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EK-H780C-OP-001

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Document:	H780-C, -D, -H, -J, -K, -L Power Supply User's Manual
Order Number:	EK-H780C-OP
Revision:	001
Pages:	35
Original Filename:

OCR Text

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EK-H780C-OP-001

power supply
user’'s manual

digital equipment corporation - maynard, massachusetts

CONTENTS
g

Page

CHAPTER 1

INTRODUCTION

1.1

GENERAL

1.2

H780 BLOCK DIAGRAM DESCRWTION

. . . . . ... .. ... ...... B

1.3

SPECIFICATIONS

1.4

RELATED LITERATURE

CHAPTER 2

INSTALLATION

2.1

GENERAL

2.2

DIFFERENCES BETWEEN 115 VAC AND 230 VAC POWER SUPPLIES

1-1

e e e e e e e e e

. . . . . . . . .. . ... .... e

. . . . . . . . . . .

e e e e e e e e e e

1-4

1-7

. . . . e

o e

2.3

SPACE REQUIREMENTS

2.4
2.5

INPUT POWER REQUIREMENTS
. . . .. e
e e e e e e e
CABLE REQUIREMENTS
. . ...
. e e e e e e e e e e

. . . . . . . . .

2.6

INSTALLATION PROCEDURE

2-1
2-1

. . .. .. ... ... .. .. ...

...

2-2

Initial Power Turn-On

. . . . . . . . . . .. . . ... ... ....

. . . ... ... .... .

. . . . . . . . ... .. ..

2.6.4

Mounting an H780 to an H9270 Backplane

2.6.5

Connecting an H780 to an H9270 Backplane

H780 Master-Slave Connection

. ..
. . .. e

. . . . . . . . . . . o

CONSOLE CONTROLS AND INDICATORS

...

. ... ... ... .. ..

2-2

24
24

e e .

2-7

... L

2-8

v v

. . . . . . . .. ... .. ... 2-11

+12 VAND +5 V ADJUSTMENT PROCEDURE

. . ... ... ... .... 2-11

2.8.1

+12
V Adjustment

. . . . ... ... ... e

2.8.2

+5S V Adjustment

. . . . ... ...

CHAPTER 3

2-]
2-1

2.6.3

2-1

. .
e
e

H780-C and H780-D Stand-Alone Operation

2.8

e e e
..

2.6.2

Connecting ACLineCord

2.7

e e e
e e

2.6.1

2.6.6

e e .12

e e e e e e e e e e 2-15
...

...

215

BASIC OPERATION

3.2

UNREGULATED VOLTAGE AND LOCAL POWER CIRCUITS

3.3

+5 V AND +12 V SWITCHING REGULATOR CIRCUITS

... .. ..

3-1

.. ... ... ..

3-2

OVERLOAD AND SHORT-CIRCUIT PROTECTION CIRCUITS

3.5

3.6

LOGIC SIGNAL GENERATION CIRCUITS

VAND +12

VCROWBAR CIRCUITS

. ... ..

3-3

. . . . . . . .. ... ... ....

. . . . . . . ... ... ....

3-5

ILLUSTRATIONS

Figure No.

Title

Page

1-1

H780 Power Supply Options

1-2

H780 Power Supply Block Diagram

. . . . . ... ... ..............
. . . . . . ... ... ..........

1-4

2-1
2-2

AC Terminal Block at Rearof H780
. . . . . . . . ... .. . . .....
H780-C, -H, and -K (115 Vac) AC Terminal Block Wiring Configuration
. ..

2-3
2-3

2-3

H780-D, -J, and -L (230 Vac) AC Terminal Block Wiring Configuration

...

1-3

ILLUSTRATIONS (Cont)

Title

Figure No.

Locations of J1 and J2 on Power Supply Board

......... e

e e

H780-C and -D Enable Plug
. . . . . .. ... .. .. e
e e e e e e
Left Side of H780 Showing H9270 Mounting Holes . . . . . . . . .. . ...

2-5
2-6
2-7

H780 Mounted to H9270 Backplane

. . . . . . . .. ... e e

2-8

H780 to H9270 Backplane Connections

2-9

Location
of H780 DC Output Connector(J4)

. . . . . . . . . . . ... ...

2-10

Pinning for H780 DC Output Connector (J4)

. . . . . .. . ... ... ...

2-11

H780 DC Output Connector (J4) with Mating DC Output Cable

A SN B

W b f:-} [ g i (N

(70-11584-0-0)

. . . . . . . . . . . .. ... ....

. . . . . . . e

H780 Master-Slave Connections

. . . . . . . . . . . o v v v v i i

Pinning for J2 (REMOTE) on Console Printed Circuit Board

. . . . . . . ..

Console Controls and Indicators

. . . . . . . . . . ... ... ... .....

Locations of H780 Adjustments

. . . . . . . . . . .. .. .. e

Unregulated Voltage and Local DC Power CII‘CUltS
Basic Regulator Circuit

. . . . . . . . .

..o

Overload and Short-Circuit Protection Circuits
Crowbar Circuit

e e e e e

e e e,
oL

. . . . . . . . . .. ... ..

. . . . . . . . . e
e

Logic Signal Generation Clrcults

........................

Power-Up/Power-Down Sequence

. . . . . . . . . . . ... ... ......

DC ON/OFF Circuit Timing

. . . . . .. ... .. .... e

TABLES
Table No.

Title
H780 Power Supply Options

. . . . . . . ... JE

Master/Slave Interface Cables

. . . . . . . .. . .. e

H780 Controls and Indicators

. . . . . . . . . . . . . .. .. ... .....

e e e e e

e e

CHAPTER 1

INTRODUCTION

GENERAL

The H780 power supply is designed to provide dc operating power for LSI-11 or PDP-11/03 systems
1.1

Six H780 options are available:

H780-C - 100-127 Vac input, no console
H780-D - 200-254 Vac input, no console

H780-H - 100-127 Vac input, with master console
H780-J - 200-254 Vac input, with master console
H780-K - 100-127 Vac input, with slave console

H780-L - 200-254 Vac input, with slave console

rs for monitoring LSI-11 or PDP-11/03
The H780 master console contains RUN and DC ON indicato
ENABLE/HALT switches for controlling
states, as well as DC ON/DC OFF, LTC ON/OFF, and
for monitoring the status of the
the processor. The slave console contains only a DC ON indicator
zed in Table 1-1 and are shown in
slave power supply. The H780 power supply options are summari
lone unit or it can be mounted to an H9270
Figure 1-1. The power supply can be used as a stand-a
for the H780, and when mounted to an
backplane. Built-in cooling fans provide forced air coolingPDP-11
/03 modules mounted in the backH9270 backplane, also provide cooling for the LSI-11 or a multiple
xing scheme provide control
plane. High frequency, low voltage, switching regulators, and
rcuit protection. Propshort-ci
and
of overcurrent, overvoltage, slow voltage buildup, low line voltage,
er power sequencing of the LSI-11 or PDP-1 1/03 power is also provided.

Table 1-1

H‘780 Power Supply Optmns

i
i

Power Supply

lnput Reqmrements

Console Supplied

H780-C

100-127 Vac
50
+£1 Hzor60
1 Hz

None

H780-D

200-254 Vac

None

H780-H

100-127 Vac
50+1 Hzor60
+1 Hz

Master

200-254 Vac
50+1 Hzor
60 + Hz

Master

50+1Hzor60+1 Hz

H780-J

H780-K

100-127 Vac

Slave

50+1 Hzor60
+1 Hz

H780-L

200-254 Vac

Slave

50+1 Hzor60
1 Hz

1.2 H780 BLOCK DIAGRAM DESCRIPTION
Figure 1-2 is a block diagram of the H780 power supply. AC line voltage is applied to the two cooling
fans and to the power transformer. The transformer has dual primary windings to meet U.S. and
European power requirements. A single secondary winding generates a stepped-down ac voltage which
is rectified and filtered to produce 26 Vdc (nominal) unregulated. The unregulated 26 Vdc is applied to
- two three-terminal regulators which produce -15 V and +5 V for the H780 internal circuits. Unregu-

lated 26 Vdc is also applied to +5 V and +12 V high frequency, high efficiency, switching regulators.
The outputs of the +5 V and +12 V switching regulators supply operating power to the LSI-11 or
PDP-11/03 system. Each switching regulator circuit is designed for good frequency stability, high
noise rejection levels, and excellent load and line regulation. An L-C output filter and a fast-recovery
diode is used in each switching regulator circuit. The +5 V switching regulator operates at a frequency
from 7 kHz to 12 kHz, while the +12 V switching regulator operates from 8 kHz to 14 kHz. Both

switching regulator circuits are protected from overvoltage, overcurrent, and short circuit outputs. In
~ addition, failsafe short circuit startup is provided, akmg with protection against a short between the
+5 V and +12 V outputs. Logic signal generation circuits within the H780 pmwde for proper power
sequencing of an LSI-11 or PDP-11/03 system, as well as the generation of the line time clock (BEVNT
L) and power supply status signals. H780-H and -J options are supplied with a console which contains
RUN and DC ON indicators for monitoring the processor and power supply states, as well as DC
ON/DC OFF, LTC ON/OFF, and ENABLE/HALT switches for controlling the systcm The H780K and -L options have a console which contains only a DC ON indicator.
|

1-2

1154

BE1e-3

H780-K and -L Power Supplies

Figure 1-1

H780 Power Supply Options

1-3

-15V

REGULATOR [~

)

15V

LOCAL DC POWER

ssy

>+
5A

REGULATOR
M

LA
PRIMARY )
POWER

>
]

| PwR |

RECTIFIER

A2V,

AND
FILTER

ckTsT

1....

‘

+5v

o\ o—al SWITCHING -

REGULATOR

—

)

| ¥V UNREG

y
;

ovfimbmm |

SHORT-CKT

PROTECTION

> +5V

OVERVOLTAGE

CKT

{CROWBAR)

l
.

"
BDCOK H

—{
8] spok n

sionaL | =

»f

aeummfim fiEvm L
CKTS

—

—{8]eracr L
-—Ds%m L

+12Vv

SWITCHING

REGULATOR

> +12V

L—-n—-—-p

JLTAGE

Vg&fl?

CP-1792

Figure 1-2

H780 Power Supply Block Diagram

1.3 SPECIFICATIONS
- The following specifications and parti
culars are for informational purposes
and are subject to change
without notice.
”
Electrical
Input Voltage (Contmuausly - see Note
100-127 Vac (H780-C, -H,
-

700,..,254 Vac (H780-D, -J, -L)

Tempomry Line D:ps Allowed

100% of voltage, 20 ms max

AC Inrush Currem

70A@127V, 60 Hz (8 33 ms)

25 A (;
@ 254 V, 50 Hz (10 ms)
input wa&r (fans mclmded)

M@ W @ full load max
W

@ full loacd
|wwm

g e
Crree
Loty
LVtey
mission and1 Susm
w:,w:; v
Sl

EREXIN

Rty B

BRI

Electrical (Cont)
[nput Protection

H780-C, -H, -K (100-127 Vac) fast blow 5 A fuse
H780-D, -J, -L (200-254 Vac) fast blow 2.5 A fuse
Hi-Pot
2 kV for 60 seconds from input to output, or input to chassis

Output Power (combinations not to exceed 110 W)
+5VISA-18A
+12V025A-35A

Maximum DC Current under Fault Conditions:
+5V Bus = 28
A
+12V Bus =95
A
+5 V Output
Total Regulation
Line Regulation
Load Regulation
Stability
Thermal Drift
Ripple

5V +3%
+0.5%
+1.0%

0 o ?QOC’“’“’S

(See Note 2)

150 mv p-p (1% for f <3 kHz)

+5 V Output

Dynamic Load Regulation

+1.2%
di/dt = 0.5 A /us
Al=5A

Noise

1% peak at f > 100 kHz (noise is superimposed on ripple)

Interaction due to +12 V

+0.05%

+12 V Output

Total Regulation
Line Regulation
Load Regulation
Stability.
Thermal Drift
Ripple
Dynamic Load Regulation

12V +£3%
+0.25%
+0.5%
0.1%/1000 hours
0.025%/° C above 25° C
350 mv p-p (1% for f < 3 kHz)
+0.8%
di/dt = 0.5 A/us
f < 500 Hz
Al =3 A

(See Note 2)

Noise

1% peak f > 100 kHz (noise is superimposed on ripple)

Interaction dueto +5 V

+ 0.2%

Electrical (Cont)
Overvoltage Protection

+5V

6.3V nm’;?ninal
min = 5.65V
max = 6.8 V

+12V

15 V nominal

min = 13.6 V

max = 16.5V
Adjustments
+5 V Output

405V -68V
-

+12 V Output

guarantee range 4.55 - 5.65 V

10,6 V-165V

guarantee range 11.7 - 13.6 V

Controls

Rear Panel
AC ON/OFF switch

|
h
Console (Master Only)
DC ON/OFF switch
Halt/Enable Switch
LTC On/Off Switch

Console Indicators
DC ON
Run
Spare

.
Master Only

Backplane Signals
BPOK H
BDCOK H
BEVNT L
BHALT L

SRUN L

Mechanical
Cooling
|
Two self-contained fans provide 30 CFM (0.7140 CMM; 200 LFPM) air flow.

Size
5-1/2 in. w X 3-1/3 in. h X 14-5/8 in. |
(1397cmw X 843 cm h X 37.15cm 1)
Weight

13 1bs (5.90 kg)
Environmental

Temperature
- Ambient 5° C - 50° C (41° F - 122° F)
Storage -40° C - 70° C (-40° F - 158° F)
Humidity
90% maximum without condensation

1-6

1.4

NOTES
'
Operation from ac lines below 100 V may cause the power supply to overheat because af decreased air flaw fmm the cooling fans.

These pammetem apply after five minutes of warmup and are measured
with an averaging meter at the LSI-11 or PDP-11/03 backplane terminal
block under system loading.

RELATED LITERATURE

In addition to the H780 print set, the Microcomputer Handbook contains useful information for instal“ling and operating the H780 power supply. Handbooks may be ordered from the nearest Digital
Equipment Corporation Sales Office.

CHAPTER 2

INSTALLATION

GENERAL
le dc power
ts of inspecting the unit, connecting a suitab
Installation of an H780 power supply consis
LSI-11 or
the
to
supply
cord, setting up the +5 V and +12 Vdc outputs, and connecting the power
|

2.1

PDP-11/03 system.

230 VAC POWER SUPPLIES
22 DIFFERENCES BETWEEN 115 VAC AND
power supplies (H780-C, -H, and -K) and the 230 Vac

H780
The main differences between the 115 Vac
power supply
are the ac input jumper configuration on the
-L)
and
-J,
-D,
(H780
H 780 power supplies
fuse; the 230
low
fast-b
A
5
witha
(115 Vac supplies are equipped
terminal block (TB1), the fuse rating
the 230 Vac
on
only
used
is
which
filter
line RFI
Vac supplies have a 2.5 A fast-blow), and the poweroperat
rewired for
be
can
-K)
and
-H,
-C,
(H780
ion
115 Vac
supplies. Power supplies factory-wired for
supplies
Vac
115
of
users
ean
Europ
er,
rs on TB1. Howev
230 Vac operation by reconfiguring the-Kjumpe
EMI
the
meet
not
will
es
suppli
these
as
ion
for 230 Vac operat
should not rewire the H780-C, -H or other
be
can
-L)
and
-J,
-D,
(H780
es
suppli
Vac
230
hand, the
requirements of VDE N-12. On the ean countr
for
ies as well as the U.S. AC wiring configurations
rewired for 115 Vac and used in Europ
raph 2.6.1.
the H780 power supplies are detailed in Parag

SPACE REQUIREMENTS
inches long
/2 inches wide £ 3-1/3 inches high X 14-5/8
The H780 power supply occupies a spacecm5-1long).
to
Space should be available to the rear of theledsupply
(13.97 cm wide X 8.43 cm high X 37.15 . H780-H,
allow
to
-J, -K and -L options should be instal an H9270
gain access to AC ON/OFF toggle switch
console. Users installing the H780 to
supply
power
for unobstructed viewing and use of the
ane.

2.3

backplane must allow for power supply space toward the right of the backpl
2.4 INPUT POWER REQUIREMENTS

at 50 +1 Hzor
e of providing 340 W (full load) of ac power
The user’s ac power source must be capabl
ty to provide
sibili
respon
with the H780 options; it is the user’s tions to the
60+ 1 Hz. No ac power cord is supplihised partic
H780 are
connec
ular application. AC power
the proper line cord and ac plug for
detailed in Paragraph 2.6.1.

2.5 CABLE REQUIREMENTS

e to the power
H780 options to connect the H780 consollisted
Three interface cables are supplied with the 1/PDP
below by
are
cables
-11/03 backplane. These
supply and to connect the H780 to the LSI-1
|

type and part number.

DEC Part No.

Cable

DC Output Cable
Power Supply Status Cable (logic cable)
Power Supply Console Cable

7011584-0-0
7011411-0K-0
7008612-0M-0

In addition, if the user is controlling an H780 slave power supply (H780~K or -L) from an H780 master
(H780-H or -J), the interface cable between the master and slaveis the user’s responsibility. This cable
can be constructed from 12-conductor ribbon cable and two 16-pin, IC-type male connectors (3M part
number 3416). The master/slave cable can be ordered from the nearest Digital Equipment Corporation Sales Office. Cable lengths and part numbers are listed in Table 2-1.
Table 2-1

Master/Slave Interface Cables

Length

DEC Part No.

4 in.

7008612-0D

6 in.
9in.
11in.
14 in.
18 in.
49 in.
2 ft.
6 ft.
10 ft.

7008612-0F
7008612-0K
7008612-0M
7008612-1B
7008612-1F
7008612-4A
7008612-02
7008612-6A
7008612-10

2.6 INSTALLATION PROCEDURE
After unpacking the H780 from the shipping container, inspect the unit and report any damage to the
nearest Digital Equipment Corporation Sales Office. Inspect for the following:

Damage to the chassis or printed circuit boards.

Loose or broken cbmponents

Damage to the console on the H780-H, -J, -K, or -L

Free rotation of the blades on the cooling fans

Proper amperage fuse (2.5 A fast-blow for H780-D, -J, and -L; 5 A fast-blow for H780-C,
-H, and -K)

Proper seating of the fuse

Proper seating of the console cable connectors (H780-H, -J, -K, and -L)

The presence of the plastic shield covering the terminal block at the rear of the H780.

2.6.1 Connecting AC Line Cord
The H780 power supplies are equipped with a terminal block (Figure 2-1) at the rear.

Jumpers on this

terminal block configure the supply for 115 Vac or 230 Vac operation (Paragraph 2.4), while two of the
terminal block screws provide a means of cannectmg ac input power to the H780. A suitable length of
No. 16 AWG, 3-conductor, stranded power cordis to be connected to the terminal block as shownin
Figure 2-2 (for H780-C, -H, and -K supplies), or Figure 2-3 (for H780-D, -J, and -L supplies). The
jumpers shownin Figures 2-2 and 2-3 are factory-installed. However, the jumper configuration can be
altered by the user to change the ac input from 115 Vto 230 V for the H780-C, -H, and -K, or from 230

Vto 115V for the H780-D, -J, and -L. European uscrL are advised not to operate an H780-C, -H, or-K

power supply on a 230 EVac lmc as these supplies are not equipped with an RFI line filter. When
mstallmg the ac line cord,remove the plastic shield cavarmg the terminal block (Figure 2-1). Terminals

2-2

should be crimped or soldered to the power cord wires. Connect the ac phase wires to the terminal
block (Figure 2-2 or 2-3), and connect the ac ground wire to the H780 chassis using the Phillips head
screw to the right of the terminal block (Figure 2-1). This screw also pmwdes a ground for the RFI
filter in the H780-D, -J, and -L supplies by means of a green/yellow wire. Make sure this wire is
reconnected to ground when replacing the screw. Be sure to replace the plasttc shield over the terminal
block after completing the wiring. Route the power cord to the top of the H780 chassis and secure it to
the chassis with a suitable strain relief, as shownin Figure 2-1. The upper-right screw at the rear of the
H780 chassis can be used to anchor a cable clamp. The free end of the power cm'd should be terminated with a connector which is suitable for the user’s requirements.

AC POWER CORD

CABLE CLAMP

smumm

PLASTIC

SCREW

SHIELD

AC ON/OFF

SWITCH

AC TERMINAL

CHASSIS GROUND

AC LINE

BLOCK

SCREW

FUSE (F1)

(TB1)

8115-1

Figure 2-1

AC Terminal Block at Rear of H780

WHITE

BLACK
GREEN

115 VAC

CHASSIS

= GROUND

— TERMINAL BLOCK

CP-2407

Figure 2-2

H780-C, -H, and -K (115 Vac)

AC Terminal Block Wiring Configuration
2-3

BLUE

BROWN } 230 VAC

GREEN/ YELLOW

[

figmmm. BLOCK

@@@@

CP-2408

Figure 2-3

H780-D, -J, and -L (230 Vac) AC Terminal
Block Wiring Configuration

2.6.2

H780-C and H780-D Stand-Alone Operation

2.6.3

Initial Power Turn-On

If an H780-C or -D power supplyis to be used as a stand-alone supply, a 510 1/4 W resistor must be
installed between J2-2 and J2-9 on the power supply printed circuit board (Figure 2-4). The 510 resistor
provides a pull-up level to an internal power supply gate, thus cnablmg the +5 V and +12 V outputs.
This resistor is not required for the H780-K or -L slave supplies, nor is the resistor required for the
H780-H and -J supplies. The resistor can be installed by bending its leads and inserting them into
socket J2, or by soldering the resistor across pins 2 and 9 of a 16-pin DIP, IC-type male connector.
Pinning for the J2 enable plugis shown in Figure 2-5.

Before connecting the dc output of the H780 to an LSI-11 or PDP-11 /03 verify the dc output voltages

by performing the following procedure:

Ifthe H780 is a slave supply (or an H780-C, -D), either cable J2 REMOTE of the slave H780
(or J2 on the power suply PC board of H780-C, -D) to the J2 REMOTE connector on the
H780 master supply (refer to Paragraphs 2.5 and 2.6.6), or install a 510 1/4 W resister into
the slave (Paragraph 2.6.2).

Connect the H780 to a suitable ac power source.

Setthe H780 AC ON /OFF switch (Figure 2-1) to ON. The fans in the H780 should operate.

On H780-H and -J options, set the console DC ON/OFF switch (Figure 2-14) to ON. The
DC ON indicator should light. (For master-slave operation, the DC ON/OFF switch and
DC ON indicator are located on the user’s master supply. The DC ON indicator on the slave
should also light.)

Using a DVM, measure the +5 V and +12 Vdc outputs at J4 (Figures 2-9 and 2-10) on the
H780 PC board (side 2). The +5 V output should not be greater than +5.15 V and the +12

'V output should not exceed +12.36 V. Perform the adjustment procedure in Paragraph 2.8 if
the outputs are out
of tolerance.

6. Set the master consbla DC ON/OFF switch to the OFF position.
7.

Set the AC ON/OFF switch to the OFF position.

Unplug the ac pcfiwer cord and connect the H780 to the LSI-11 or PDP-11/03 system.

2-4

‘

Figure 2-4

81156

Locations of J1 and J2 on Power Supply Board

5100 174w

RESISTOR

13\12

———

AT,

c—————

T
.

CP-2409

Figure 2-5

H780-C and -D Enable Plug

2.6.4 Mounting an H780 to an H9270 Backplane
The H780 power supply is designed to be mounted to the LSI-11/PDP-11/03 H9270 backplane. Four

holes on the left side of the H780 are equipped with No. 8-32 threaded bosses (Figure 2-6). These holes
mate with four holes in the right side of the H9270 backplane frame. Four No. 8-32 X-1/2 inch screws
are inserted through the H9270 backplane holes and are threaded into the H780 power supply. The
H9270 backplane and the H780 power supply thus become one assembly (Figure 2-7). Figure 2-6

shows the location of the four mounting holesin the H780. The two screws securing the front chassis
pdmtmn must be removed. These screws are to be replaced with langer screws (1 /2 inch) whcn attaching the H780 to the H9270.
E

#8-32 THREADED HOLES
FOR MOUNTING H9270

REMOVE THESE SCREWS
AND REPLACE WITH

#8-32 X 1/2” WHEN

MOUNTING H9270

8115-5

Figure 26 Left Side of H780 Showing H9270 Mounting Holes

811512

Figure 2-7

H780 Mounted to H9270 Backplane

2-6

Connecting an H780 to an H9270 Backplane

2.6.5

The H780 power supply is connected to the H9270 by means of two cables, These cables are supplied
with the H780 (refer to Paragraph 2.5). One of these cables is a 10 inch logic signal cable (DEC part

number 70-11411-0K-0) which connects from J1 on the power supply board (Figure 2-4) to connector

pins on the H9270 printed circuit board (Figure 2-8). Either end of this cable can be connected to the
power supply or the backplane. The other cable is a 12 inch dc output cable (DEC part number 701 1584-0-0). This cable is terminated at one end with a keyed, 12-pin connector which mates with J4 on
side 2 of the H780 power supply board. Figure 2-9 shows the location of J4; Figure 2-10 shows J4
pinning. The remaining end of the dc output cable is terminated with a 6-lug connector strip which is
connected to the H9270 backplane terminal block, as shown in Figure 2-8. When connecting the 6-lug
connector strip to the H9270 backplane, make sure that the spade lug connectors are facing up. Figure
2-11 shows the dc output cable connected to J4 of the H780. The H780 logic signal and dc output
cables are routed toward the rear of the power supply and exit from the supply chassis next to the
|

H9270 backplane terminal block.

CONSOLE
/p*c‘ BOARD

|
J4 12-PIN CONNECTOR

31 (SUPPLY)

2 OF PC. BOARD)
(SIDE

‘

H780 POWER SUPPLY

AC LINE
NE CORD

O NRECTOR “Z/SOCKET

CONNEC

PWR XFMR‘

Y S—

WER CABLE (12in.)

?fomsamowm

cL3L

BEVNT L—\

AR
pe—

) (70-08612-0M-0)

SIGNAL PIN SIGNAL
9 +5A
+5A

SRUNL

DCONH 10 SPARE
SPARE
SRUNL

GROUND

13 GROUND

6
7
8

L
Cs3

9
10

BEVNTL
(KEY)

CL3 L
C€S3 L
SPARE

BHALT L
DCOK H

4
6
7
8

CONSOLE
POWER
SIGNAL/

“—PIN
{1

‘

{

SIGNAL
BPOK H

SIGNAL CABLE (10 in.)J
(70-11411-0K=0)

16-PIN SOCKET

"L_pIN
{
|

—

}

P.C. BOARD

BEVNTL
CL3
C€S3
SPARE

12 GROUND
14 DC OKLEDH
{5 SPARE
16 B HALT L

CONNECTOR PINS ON

' H9270 P.C. BOARD

% o3 & &+— BDCOK H
|

D ] 5V
oecTor | “~T-HZ
SCONNECTOR
STRIP

+5vB

D
]

Q@ @& eo—BHALT L

H9270 BACKPLANE REAR VIEW

(P.C. BOARD SIDE 2)

W__‘GW
|
SRUN L

BPOK H

]GND

TERMINAL BLOCK

CP-1825

Figure 2-8

H780 to H9270 Backplane Connections

2-7

DC OUTPUT
CONNECTOR

811611

Figure 2-9

Location of H780 DC Output Connector (J4)

the H780 and connected to
H780-H. -J. -K, and -L power supplies have a console that is attached to
2-OM-0). This cable is
70-0861
number
part
the supply by means of a console signal /power cable (DEC 2-4) to J1 on the console
PC board (refer
factory-installed from J2 on the power supply board (Figure
to Figures 2-8 and 2-12).

lave Connection

H780 Master-S
an H780-K or -L slave
An H780-H or -J power supply can be used as a master supply to control
LSI-11 or PDP-11/03
down
r
up/powe
supply. This master-slave arrangement allows the user to power
ed to the master
connect
is
supply
slave
The
expander backplane logic from the master supply console.
circuit board,
printed
console
supply
master
supply by means of the J2 (REMOTE) connector on the
necting cable
intercon
The
board.
circuit
and J2 (REMOTE) on the slave power supply console printed and a suitable length of 12-condu
ctor
rs
connecto
male
is the user’s responsibility. Two 16-pin, IC-type
h
Paragrap
to
(refer
cable
necting
intercon
the
t
construc
to
cable (preferably ribbon type) can be used
J2
and
Y)
(SUPPL
J1
the
of
s
location
the
and
boards
circuit
printed
2.5). Figure 2-12 shows the console

2.6.6

2-8

(REMOTE) connectors. J1 is always connected to J2 of the power supply printed circuit board (Figure
2-8) by the console signal/power cable (DEC part number 70-08612-OM-0) which is factory-installed.
~ Pinning for J2 (REMOTE) on the console printed circuit board is shown in Figure 2- 13. Pinning for J2
on the power supply printed circuit board is indicated in Figure 2-8.
PIN NO.

4
—

—
CONNECTOR .
KEY WAYS (6)
&

—

|
'

)

+5V OUTPUT

—

| m—

)

—

)

—

412V OUTPUT

—

{

————— 412V RETURN

:
NOTE

+5V RETURN
‘

CP-2410

VIEWED FROM BOTTOM OF

POWER SUPPLY P.C. BOARD

Figure 2-10

Pinning for H780 DC Output Connector (J4)

81159

Figure 2-11 H780 DC Output Connector (J4)
with Mating DC Output Cable (70-11584-0-0)
29

J1 {SUPPLY) CONNECTED TO J2 ON

POWER SUPPLY P.C. BOARD OF MASTER

‘

J2 (REMOTE) CONNECTED TO J2 (REMOTE)

ON SLAVE SUPPLY INDICATOR P.C. BOARD

8116.2

)

H780-H and -J (Master)

J2 ON
J1 {BUPPLY) CONNECTED TO

POWER SUPPLY P.C. BOARD OF SLAVE

“

‘)

F
CON ECT TO J2 (REMOTE)
122 (REMOTE)
ON CONSOLE P.C. BOARD OF MASTER

H780-K and -L (Slave)
Figure 2-12

H780 Master-Slave Connections
2-10

————"

A———

A————

M-

m—-

———

—————

J2 (REMOTE)
PIN

SIGNAL

PIN SIGNAL

NO CONNECTION

DCONH

SPARE3

NOCONNECTION

SPARE4

SPARE 2

SPAREGB

GROUND

ClaL

DCOKH

CSs3L

SPARES®

SPARE 1

NOCONNECTION
CP-24i1

Figure 2-13

Pinning for J2 (REMOTE) on Console Printed Circuit Board

2.7 CONSOLE CONTROLS AND INDICATORS
|
The H780-H or -J master console has three LED indicators and three, two-position,
toggle switches.
One of the LED indicators is a spare indicator. Circuitry to drive this indicator is
included on the
console printed circuit board for user application. The console on the H780-K and -L slave supplies
has only one LED indicator - DC ON. Figure 2-14 shows the H780 console controls and indicators;
they are described in Table 2-2. Additionally, the rear panel of the H780 contains an AC ON/OFF
toggle switch and an ac line fuse (Figure 2-1).
|

2.8 +12V AND +5V ADJUSTMENT PROCEDURE
‘The H780 power supply is factory-adjusted to produce +12 V and +5 V outputs within
the operating
tolerance of an LSI-11 or PDP-11/03 system. The adjustment procedures presented allow
the user to
trim the dc outputs of the H780 to meet his particular needs. One adjustment is provided for the
+12 V
output, while two adjustments (one for the output voltage and one for the switching regulator
frequency) are provided for the +5 V. Figure 2-15 shows the locations of the adjustments. A DVM,
an
oscilloscope, and a small screwdriver are required. Power supply loading is provided by the LSI-11 or

PDP-11/03 system.

2-11

SPARE INDICATOR
811510

H780-H and -J Console

DC ON INDICATOR

81731

H780-K and -L Console

Figure 2-14

Console Controls and Indicators
2-12

+12 V OUTPUT

ADJUST (R87)

CCW - INCREASE
CW - DECREASE

+6V FREQUENCY

ADJUST (R69)

CW - DECREASE
CCW - INCREASE

+5 V QUTPUT

ADJUST (R88)

CCW - INCREASE

CW - DECREASE

511568

Table 2-2
Control /Indicator

DC ON

H780 Contmlsynd Indicators

- Type

}

Function

Illuminates when the DC ON/OFF
toggle switch is set to ON and proper
dc output voltages are being produced

LED indicator

by the H780.

If either the +5 V or +12 V output
from the H780 is faulty, the DC ON

indicator will not illuminate. This is
the only indicator on the H780-K and
-L slave supplies.

RUN

Illuminates when the LSI-11 or PDP11/03 processor is in the run state (see

LED indicator

ENABLE/HALT).

SPARE

Not used by the H780 or processor.

LED indicator

The H780 contains circuitry for driving this indicator for user
applications.

- DC ON/OFF

Two-position toggle switch

When set to ON, enables the dc outputs of the H780. The DC ON
indicator will illuminate if the H780
dc output voltages are of proper values. If a slave supply is'connected to a
master, the slave DC ON indicator
will light if the slave dc output voltages are of proper value.

When set to OFF, the dc outputs from
the H780 are disabled and the DC ON
indicator is extinguished. If a slave
supply is connected to a master, the
slave DC ON indicator will also
extinguish.

ENABLE/HALT

Two-position toggle switch

When set to HALT, the B HALT L
line from the H780 to the processor is
not asserted and the processor is in the
run mode (RUN indicator
illuminated).

When set to ENABLE, the BHALTL
line is asserted allowing the processor
to execute console ODT microcode
(RUN indicator extinguished).

2-14

Table 2-2

Control/Indicator

LTC ON/OFF

H780 Cflntmls and !ndicatms (Cont)

| Type
S

jé'’I’wo»-»;;u:mi’tinz:m mggle sWitch
|

Functinn

When set to ON, enables the generation of the line time clock (LTC) by

the H780.

When set to OFF, disables the H780
line time clock.
AC ON/OFF (rear panel)

| Two-position toggle switch

When set to ON, applies ac power to
the H780.

When set to OFF, removes ac power
from the H780.
FUSE (rear panel)

5 A or 2.5 A fast-blow

Protects H780 from excessive current.
H780-C, -H, and -K use a 5 A fuse,

H780-D, -J, and -L use a 2.5 A.

2.8.1
+12 V Adjustment
|
Perform the following procedure when adjusting the +12 Vdc output:

Apply power to the LSI-11 or PDP-11/03 system and allow a five minute warmup period.

Using a DVM, measure the +12 V output at the LSI-11 or PDP-11/03 backplane terminal
block (refer to Figure 2-8).
|

Using a small screwdriver, adjust R87 (Figure 2-15) until the DVM indicates +12.0 V
(+11.64 V to +12.36 V acceptable range). Turning R87 CW decreases the +12 V output,
while turning CCW increases the output.
NOTE

If R87 is turned too far CCW, the +12 V output will
crowbar and drop to approximately 0 V. This will
occur between +13.0 V and +16.5 V. Do not allow
the supply to crowbar as this may blow the internal
fuse (F1) protecting the +12 V regulator.
4.

Using an oscilloscope, measure the ripple on the +12 V output at the backplane terminal
block. The ripple should not be greater than 350 mV peak-to-peak.

2.8.2 +5 V Adjustment
|
Perform the following procedure when adjusting the +5 Vdc output:
I.

Apply power to the LSI-11 or PDP-11/03 system and allow a five minute warmup period.

Using a DVM, measure the +5 V output at the LSI-11 or PDP-11/03 backplane terminal
block (refer to Figure 2-8).

2-15

Using a small screwdrwcr adjust R88 (Figure 2-»15) untnl the DVM mdwates +35. 0 V (+4.85

Vto +5.15 V acceptable range). Turning R88 CW decreases the +5V output whfle turning

CCW increases the output.

NOTE

If R88is turned too far CCW, the +5 V output will

crowbar and drop to approximately 0 V. This will
occur between +5.6 V and +6.8 V. Do not allow the
supply to crowbar as this may blow the internal fuse
(F2) protecting the +5 V regulator.

Usmg an oscilloscope, measure the amplitude and frequency of the ripple on the +5V
output at the backplane terminal block. The ripple should not be greater than 150 mV peakto-peak with a period from 80-140 us. If the ripple periodis not within 80-140 us, adjust
R96 (Figure 2-15). Turning R96 CW decreases the ripple period, while turning CCW
increases the period. After adjusting the ripple period, recheck the +5 V output (steps 2 and
3).

2-16

CHAPTER 3
BASIC OPERATION

3.1

GENERAL
This chapter contains a functional
description of the H780 power suppl
y. Major functions contained in
the
H780 were introduced in Paragrap
h 1.2 and illustrated in Figure
1-2. These functions include
circuits which produce unregulated
voltage and local power for the H780
internal circuits, +5 V and
+12 V switching regulators, over

(overvoltage protection) circuits,

load and short-circuit protecti

on circuits, +5 V and + 12 V crow
bar
and logic signal generation circuits.

3.2 UNREGULATED VOLTAG
E AND LOCAL POWER CIRCUI
TS
Unregulated voltage and local powe
r circuits provide operating dc powe
r for power supply logic and
control circuits, and dc power for
the +5 V and +12 'V regulator circu
its. These circuits are shown in
Figure 3-1. AC power is supplied to
the H780 via an ac input plug and
cable. A toggle switch mounted
on the rear of the H780 applies ac
power to the power supply. Normally
, this switch remains in the ON
position, allowing ac power to be
controlled by power distribution
and
control circuits in which the
LSI-11 or PDP-11/03 system is
installed. Primary circuit overload
prote
ction is provided by a fuse
mounted
on the rear of the H780.

\/OFF

ONO

(e
'

PWR

XFMR

q') 3

FAN

WER

(115v)

—

:
1

FAN

oo—

‘

SWR

ON/OFF

o wR

230V 1 j |

Figure 3-1

“;L

)

—

- &gg crg GN
LOG!

IGNAL

‘

— ) GENERATION

CKTS

me
o

Yy | %

T
=

sas

TRANS
IENT
LU

fz‘i"év PRIMARY POWER CONNECTIONS
|

__
S

’

41|

L‘*mm”*m“ m-—.-—-mmJ

UNREG

3-TERMINAL
REGULATOR

(+5V)

+5V

=
3-TERM INAL

*] REGULATOR

|—» -i5v

(-15v)

CP-1T93

Unregulated Voitage and Local DC Powe

r Circuits

Primary power circuits are factory~wired for 115 Vac (H780-C, -H, -K) or 230 Vac (H780-D, -J, -L)

operation. Power transformer pnmary wmdmgs and the two fans operate directly from the swwtchcd ac
power.

A single center-tapped sccan,dary winding wpplies power for rcgulamr circuits and internal circuit
operation. Conventional fullwave rectifiers and a -15 V, 3-terminal regulator IC provide regulated
voltage for internal distribution. The rectifiers also provide +24 V (approx) for internal distribution
and regulator operation. A 3-terminal regulator integrated circuit provides +5 V logic and control
power for H780 circuits. The +5 V and +12 V regulators use the same +24 V unregulated voltage for
regulation and distribution to the processor modules. AC voltage from one side of the transformer
secondary is also routed to the line time clock (LTC) circuit, which generates a BEVNT L bus signal
for a line time clock processor interrupt. When used with a 60 Hz line frequency, the interrupt occurs

at 16.667 ms intervals; a 50 Hz line frequency will produce interrupts at 20 ms intervals.

33 45V AND +12 V SWITCHING REGULATOR CIRCUITS
Both +5 V and +12 V regulator circuits receive the +24 V unregulated input power. The +5 V and
+12 V regulator circuits are identical except for component values. Hence, only the basic +5 V regulator is described in detail.

The basic regulator is a switching regulator which operates at approximately 10 kHz. The main controlling element is a 3-terminal regulator which operates at approximately the regulated output voltage
level. Basic regulator circuits are shown in Figure 3-2. Note that the ground terminal of the 3-terminal
regulatoris connected to a circuit that allows adjustment of the terminal voltage over a-0.7V - +1.5
V range. Hence, the 3-terminal regulator output in the +5 V regulator circuit can range from 4.3 V 6.8 V (approx).
SNUBBER

DI12E 2R15
1
!

Y+

FREQ.

R34 :.»‘

R27
ANN

R14

|
|

|CONTROL
!

BSSPE. S—

arz-c |

1 co

D32

aye- '
PART OF Dg
‘wmmw

WHEELING

o
| &

TO OVERLOAD

DIODE

AND
SHORT-CIRCUIT

1
=

PROTECTION
CKT.

|
=

3-TERM.
flEfi Lhmfl

L_t+sv)

2RIB

SR33

€10 A~

——

ADJ.

@T
= |

Ipmrecm

SENSE

FREE

1
TCZ

CURRENT

NETWORK

¥-

CROWBAR

ekt

w41 .5V

+svapu. ADJ.)
RE8SS (FACTORY-

R17

IV AN Ie07 07V
=
CP~1794

Figure 3-2

Basic Regulator Circuit

3-2

Normal switching regulator operation is accom

ward-bias for the control transistor is

plished when the control transistor is turne

supplied via R 14. It is turned off only
during fault

(overcurrent or shorted output voltage) or when

the input ac line voltage is below

d on. For-

conditions

specifications. Its
emitter supplies unregulated voltage to the 3-term
inal regulator. At less than 50 mA regulator outpu
t
current (approx), the 3-terminal regulator
supplies the output voltage. However, as load
curren
t
through the 3-terminal regulator is increased
beyond this value, the voltage drop across
R27
forwa
rdbiases the driver transistor. The pass switch transi
stor then turns on and applies the unregulated
+24 V
to L2. The outpu

t capacitor then charges toward the +5 V
value, current limited by the inductance of
L2. When the output voltage rises to the 3-term
inal regulator regulation voltage, the 3-term
inal regulator turns off;

current through R27 stops, and the driver transi
stor is not forward-biased. Hence, the
driver and pass switch transistors cut off.
The energy stored in L2 continues to charg
e the capacitor
bank slightly beyond the designed output
voltage via the free-wheeling diode and the
current sense
resistor. Once the inductor’s stored energy
is spent, the load discharges the output capaci
tor until the
output volta
ge drops below the 3-terminal regula
tor’s regulation voltage. At that point,
current

TM through R27 increases and turns

on the driver and pass switch transistors,

‘that as the load is increased, the pass switc
capacitor to the regulated voltage value.

ing regulator operation.

and the cycle repeats. Note

h must remain on longer in order to charg

This process repeats at a 7-12 kHz rate,

Switching losses in the pass switch transi

e the output

producing the switch-

stor are minimized by the snubber netwo

operates during the “off” switching

transient (as the pass switch is biased-off

rk. This network

) by controlling the rate of

increasing collector to emitter voltage as collec

tor current decreases.
The control transistor is turned off durin
g a fault condition by overload and short
-circuit protection
circuits. When a fault condition is detec
ted, the control transistor’s base volta
ge drops to nearly 0 V,
~causing it to cut off. When cut
off. operating voltage is removed from
the 3-terminal regulator and R27
current is 0, disabling the switching
regulator circuit.

3.4 OVERLOAD AND SHORT-CIRCUI
T PROTECTION CIRCUITS
Each H780 dc output is overload and
short-circuit protected. When in an over
load condition, excessive
power
supply current is sensed, causing

both switching regulators to go

off and then cycle on and off at
a low-frequency rate (approximately
7.5 Hz) until the overload is remo
ved. Each time the power
supply cycles on, the circuit checks
for the overload condition. If the load
current returns to normal,
the 10 kHz switching regulator

operation resumes.

Overcurrent sensing circuits for +5
V and +12 Vdc outputs are identical
except for component values.
A 5 V power supply overcurrent condi
tion results in an increased voltage
drop across the current sense
resistor (Figure 3-3), forward-biasing
the current sense transistor. (During
normal operation, this transistor is not forward-biased.) Current
sense transistor collector (Q8) voltage
then drops from the normal +24 V (approx) to the +5 V regul
ator output value; this voltage, whic
h is less than the +13.8 V
reference applied to the current limit
comparator’s inverting input, is diode
-coupled to the comparator’s nominvcyting input,
causing the comparator’s output

to go lmnfi; the diode coupling provi

des

output signal triggers the 50 us one-s

hot, whose OVERCURRENT L

pulse output triggers the 135 ms
one-shot and sets the Current Limit
flip-flop. The OVERCURRENT L
pulse is also ORed with the
POWER OFF L signal, turning on the
+5 V and +12 V hold-off transistors.
Both switching regulators
are then disabled. The high 135 ms
one-shot output pulse is ANDed with
the
Current Limit flip-flop
output, turning on +5 V
and +12 V extended hold-off trans

istors. Hold-off signals remain

and inhibit switching regulator opera

ms one-shot resets, terminating
the

tion for the 135 ms pulse duration.

delayed hold-off signals, and trigg

low output resets the Current Limit

in this state

At the end of this time, the 135

ers the 2 ms one-shot. Its active

flip-flop and clears the 135 ms one-s

hot for 2 ms, allowing the
regulator pass switch transistors to
operate for 2 ms (minimum). At the
end of this time, the 135 ms
one-shot is again enabled (the clear
input goes high) and a new overcurren
t cycle is enabled. If the
overload is removed, normal operation
resumes; otherwise, the overload cause
s a new overload condition to occur and the cycle

repeats, as described above.
3-3

LOW FREQ CKT

[ParToF+sv
~— — — |
SWITCHING REG

— e

R20S

CURRENT

frivia

[

SENSE

10 LoAD

C6 |
CURRENT
(17 - +5V
L2V SIRRE

+5V HOLDOFF L

CURRENT

;
'
(EXTENDED)|

CURRENT

TRANSISTOR

—@_

'/Q12-D

D20
FRK”W *f2\/

TRANSISTOR
+V

D19

‘w

R58

UNREG —1——AAN

13.8V{(NOM.)

COMPARATOR

(EXTENDED)

50
Us |

ONE- |

A==
RS9

‘

’-

(YA

SHOT
£E6 |

| B

\Dy/ 01274

+5V HOLDOFF L

”

L D13

X 014

POWER OFF L

FROM LOGIC SIGNAL ——
GENERATION CKTS

'Dég

+12v HOLDOFF L

Q12-8B

CP-1796

Figure 3-3

Overload and Short-Circuit Protection Circuits

Switching regulator operation is suspended when the operator places the DC ON/OFF switch in the
OFF position. Logic signal generation circuits respond by immediately asserting BPOK H low to
initiate a processor power-fail sequence. After a 5-10 ms *““pseudo delay,” POWER OFF L is asserted
low. This low signal is wire-ORed with OVERCURRENT L, inhibiting the switching regulator oper-

ation, and dc power is removed from the backplane.
3.5 +5V AND +12 V CROWBAR CIRCUITS
|
Crowbar circuits are connected across both +5 V and +12 V power supply outputs for overvoltage
protection. An overvoltage condition could occur if +12 V and +5 V outputs shorted together, of if a
~driver or switch transistor becomes shorted. When shorted to a higher voltage source, the crowbar
fires, shorting the supply voltage that is protected to ground (dc return). In this condition, the overload
and short-circuit protection circuits respond by limiting the duty cycle of the switch transistor until the
overvoltage source is removed. However, when the overvoltage is caused by a shorted driver or switch
transistor, short-circuit protection is ineffective, and the excessive current caused by the crowbar circuit firing will blow the regulator’s fuse (F1 for +5
V or F2 for +12 V).
The crowbar circuit for the +5 V output is shown in Figure 3-4. It comprises a 5.6 zener diode D9,
diode D8, programmable unijunction transistor Q9 and silicon-controlled rectifier (Q15). Q15, R19,
D8, and D9 supply the 6.1 Vdc (approx) crowbar reference (threshold) voltage
to the gate of Q9 via
R21. Q9 is normally off and its cathode supplies a 0 V gate input to Q15. An overvoltage is coupled
into the circuit via C7, causing the gate voltage of Q9 to rise; this triggers Q9 and its cathode voltage
rises to the output (overvoltage) potential. Q15 then fires and shorts (crowbars) the supply output. The
circuit remains in this condition until the overvoltage is removed (Q15 current goes to zero) and either
the power supply switch transistor is off, due to short-circuit protection, or the regulator’s dc fuse
opens.

3-4

+5V

> +5V

+s5v | Gle,

SWITCHING) C2L,

REGULATOR |

a1s

OUTPUT

...,

RTN (GND)
CP-1797

Figure 3-4

Crowbar Circuit

The +12 V crowbar circuit functions in a similar manner. However, the reference voltage for this
power supply is approximately 13.5 V.

3.6

LOGIC SIGNAL GENERATION CIRCUITS

Logic signal generation circuits produce LSI-11 bus signals for power normal/power fail and line time
clock interrupt functions and processor Run-Enable/Halt mode. The RUN indicator circuit monitors
the SRUN L backplane (nonbused) signal and provides an active display when the processor is in the
Run mode. BPOK H and BDCOK H indicate power status. When both are high, power to the LSI-11
bus is normal and no power fail condition is pending. However, if primary power goes abnormally low
(or is removed) for more than 16.5 ms, BPOK H goes low and initiates a power-fail processor interrupt. If the power-fail condition continues for more than an additional 4 ms, a “pseudo delay” circuit
causes BDCOK H to go low. The circuit also causes the overload and short-circuit protection circuit to
inhibit +5 V and +12 V control transistors; normal output voltages are available for 50 us (minimum)
after BDCOK H goes low (depending on the loading of the dc output voltages). The DC ON/OFF
switch simulates an AC ON/OFF operation by turning switching regulators on or off without turning
system primary power off. A normal power-up/power-down sequence is produced by this circuit. The
line time clock circuit produces a processor interrupt at the power line frequency (either 50 or 60 Hz).
The circuit simply asserts the BEVNT L line at the line frequency.

DC voltage monitor circuits respond to both +5 V and +12 V power supply outputs. A +2.5 V
reference at the voltage comparator’s noninverting input is established by +5 A and a voltage divider
~comprised of R25 and R3, as shown in Figure 3-5. Voltages are sensed at the anodes of diodes D17 and
D35s.

The sensed voltage to the voltage comparator’s inverting input is normally 5 V, causing the comparator’s output to go low. The low signal forward-biases DC ON panel indicator driver transistor
Q10, producing a DC ON indication, and reverse-biases the BDCOK H FET bus driver Q6. As a
result, Q6 cuts off, and its source voltage rises to +5 V, producing the active BDCOK H signal.
When either (or both) power supply output is 0 V, the voltage at the voltage comparator’s inverting

input is less than the +2.5 V reference. Hence, the comparator’s output goes high, turning off the DC
ON indicator and allowing Q6 to conduct. Q6 asserts the BDCOK H signal low, indicating that a dc

power-fail condition exists. When normal power is restored, as during the power-up sequence, C137
charges via R50. When the C37 voltage exceeds the +2.5 V reference, the comparator’s output then

goes low (normal).

+5V

R45

VOLTAGE

SENSE INPUTS

}
+5A

45V

#12V

'}—106

BDCOK H

+5A

D35E&

OI7K

‘
+5A

SR25

RSO ‘

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VOLTAGE

D119

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:
+2.5V /

;

0 C OK L R39
AAN

Q10

% D15

R30

R3S
'

R35

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+5A—w—1e—0C LOH| cover
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c19

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D27

POWER OFF L

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R91

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SRUN L

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» PROTECTION
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- CIRCUIT
CKTS

D26

D3
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TO OVERLOAD AND

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ACV{ D2

DC OFF VOLTAGE

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2.5y

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RUN

+5A

CHALT H

BHALT L

CP-1798

Figure 3-5

Logic Signal Generation Circuits

3-6

AC voltage monitor-circuits include an ac low comparator, a 16.5 ms delay, and a BPOK H bus driver
circuit, whichis enabled only when BDCOK H is in the active (dc voltage normal) state. Rectifiers D2
and D3 produce positive-going dc voltage pulses at twice the ac line frequency. R32, R12, and C1

produce nominal +3.9 V.(paak) normal line voltage pulses which are coupled to the noninverting mput

of the ac low comparator via R48. R8 and R9 produce a +2.5 V reference for the comparator’s
inverting input. The comparator’s normal output is a series of pulses occurring at twice the ac power
line frequency. Each positive-going leadmg edge retriggers the 16.5 ms one-shot, keeping it in the set
state. The 16.5 ms one-shot output is diode-ORed with DCOK L via diodes D25 and D23 and PWR
OFF H via D24. Normally, the three signals are low and Q11 remains cut off. In this condition, C4
charges to +3.125 V via R36 and R38. This signal is then applied to the power OK comparator’s
inverting input via R24. Since the noninverting input is referenced to +2.5 V by voltage divider R5 and
R6, the comparator’s output goes low, biasing off FET Q5. Q5’s source voltage then rises toward +5 V
via R46, producing the active BPOK H signal. Powcr«up/powewdown sequence timing is shown in
Figure 3-6.
(:'h

AC INPUT

;

é
BPOK H

—’l 15-24ms (&

’4— TOW(WN)-O!

—

4ms(min)

}0-—-

BDCOKH
|

lt-ammms

k—-imm(mm)

DC QUTPUT
VOLTAGES

~ POWER UP

— POWER DOWN

>
cP-1823

Figure 3-6

Power-Up/Power-Down Sequence

A power failure is first detected when the pulsaimg dc voltage at the ac low comparator’s noninverting
input is less than +2.5 V (peak). The comparator’s output then remains low, allowing the 16.5 ms oneshot to go out of the retrigger mode. The one-shot resets 16.5 ms after the leading edge of the last valid
ac voltage alternation; the 16.5 ms delayis equivalent to a full line cycle (twwalt&mam) failure. The
high one-shot output is then coupled via D23 to the base of Q11, forward-biasing it. Q11 conducts and
rapidly discharges C4; R36 limits peak discharge current.
The low voltage thus pmducedis less than the +2.5 V reference at the power OK comparator’s input,
and its output goes high. QS5 then conducts and asserts the BPOK H signal low (power faxl) The AC
LO H signal produced by the 16.5 ms one-shotis coupled via D34 to C39 on the inverting input of AC
OK comparator ES. When C39’s voltage rises above 2.5 V, the comparator’s output goes low, turning

off the DC ON indicator and negating BDCOK via the de voltage monitor circuit, and turns off the
regulator circuits by asserting POWER OFF L via D27.

3-7

When normal power is restored, the 16.5 ms one-shot returns to the retrigger (set) mode. ACLOH

goes low and enables the dc voltage monitor and,regulamr circuits. The low AC LO H signal also
removes forward bias from the base of Q11, cutting it off. Its coilacmr voltage then rises as C4 charges
at la relatively slow rate. R38 controls the chargmg rate of C4 and ensures that ac voltage and dc output
voltages are normal for appmmmawly 100 ms (70 ms minimum) before BPOK H goes high.

The DC ON /OFF switch simulates a power failure when it is placedin the OFF pomtmn Crosscoupled inverters provide switch debounce protect on and a low (false) DC ON H signalis produced.
This signalis inverted to produce a high PWR OFF H signal thatis coupled via D26 to the “pseudo
delay”TM circuit, causing a power fail sequence to occur, and to Q11 via R53 and D24, causing BPOK H
to go low (power fail mdwation) After a 5-10 ms (approx) “pseudo delay,” C13’s voltage rises above
the dc off voltage comparator’s +2.5 V reference (noninverting) input. The comparator’s output goes
low, asserting POWER OFF L low and turning off the switching regulators. When the DC ON/OFF
switchis returned to the ON position, PWR OFF H goes low, rapidly discharging C13. POWER OFF
L. then goes high and switching regulator operation resumes. Approximately 100 ms later, BPOK H
goes high and normal processor operation is enabled. DC ON/OFF circuit timing is shown in Figure
3-7.
ON

DC
ON/OFF
SWITCH QFF

—

4ms{min)

“"{ }“'“5"10“5

BPOK H

I
'4-—-—— 70m(min)~——-¢!

tmm(min)-——l }‘-— )

| "—f* l‘-—-—B’mu(miM

BDCOK H
DC OUTPUTS

|
e

DC OFF

/
xf::.

DC ON

>
CP-1824

Figure 3-7

DC ON/OFF Circuit Timing

BEVNT L is the bused EVENT line which is normally used for line time clock interrupts. Q4 is cut off
and QI is forward-biased during negative alternations of the ac line, producing low-active BEVNT L
signals. DI clips negative alternations and limits Q4’s reverse-bias to emitter voltage. The LTC
ON/OFF switch must bein the ON position for BEVNT L signal generation. When the LTC function
is not desired, the LTC switchis set to the OFF position; CSPARE2 goes low. Ql remains cut off, and
BEVNT L remains passive (high).
The RUN indicatoris illuminated whenever the processor is executing programs. SRUN L, a nonbused backplane signal, is a series of pulses which occur at 3-5 us intervals whenever the processor is in
the Run mode. The pulses trigger a 200 ms one-shot on each SRUN L pulse leading edge, keeping it in

the retrigger mode. Its high RUN H output signalis then inverted, producing a low signal that turns
on the RUN indicator. When the processor is in the Halt mode, SRUN L pulses cease and the 200 ms
one-shot resets after the 200 ms delay. The RUN indicator turns off, indicating the Halt mode.
The HALT/ENABLE switch allows the operator to manually assert the BHALT L signal low, causing
the processor to execute console ODT microcode. When in the ENABLE position, BHALT L is not
asserted, and the Run mode is enabled. Cross-coupled inverters provide a switch debounce function.

3-8