Vicor Corp.

Tel: 800-735-6200, 978-470-2900 Fax: 978-475-6715

28V Micro Family

Rev. 1.2

Page 6 of 11

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Module Enable/Disable

The module may be disabled by pulling PC below 2.3 V with

respect to the –Input. This may be done with an open collector

transistor, relay, or optocoupler. Multiple converters may be

disabled with a single transistor or relay either directly or via

“OR’ing” diodes. See Figure 1.

Primary Auxiliary Supply

At 5.7 V, PC can source up to 1.5 mA. In the example shown

in Figure 3, PC powers a module enabled LED.

Module Alarm

The module contains “watchdog” circuitry which monitors

input voltage, operating temperature and internal operating

parameters. In the event that any of these parameters are

outside of their allowable operating range, the module will

shut down and PC will go low. PC will periodically go high

and the module will check to see if the fault (as an example,

overtemperature) has cleared. If the fault has not been cleared,

PC will go low again and the cycle will restart. The SC pin

will go low in the event of a fault and return to its normal

state after the fault has been cleared. See Figures 2 and 4.

Disable

Disable = PC <2.3V

+In

PC

PR

–In

Figure 1 — Module enable / disable.

Figure 3 — LED on-state indicator.

4k

Ω

"Module

Enabled"

+In

PC

PR

–In

Optocoupler

+In

PC

PR

–In

4k

Ω

Alarm

1.00 V

+OUT

SC

–OUT

Comparator

Input Undervoltage

Input Overvoltage [a]

Over Temperature

Module Faults

2-20 ms typ.

Auto

Restart

5.7 Vdc

(0-3 mA)

50

Ω

SW2

SW3

1.23

Vdc

6 K

1 K

SW1

SW1, 2, & 3 shown

in "Fault" position

+OUT

SC

–OUT

+IN

PC

PR

–IN

1 M

Figure 2 — PC/SC module alarm logic.

Figure 5 — Isolated on-state indicator.

2-20ms typ.

Fault

SC

PC

1.23V

5.7V

40

μs typ.

Figure 4 — PC/SC module alarm timing.

Figure 6 — Secondary side on-state indicator.

CONTROL FUNCTIONS - PC PIN