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

V375C3V3C75B DC-DC Converter

Rev. 3

Page 4 of 8

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CONTROL FUNCTIONS - PC PIN

Module Enable/Disable

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

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

1.00V

+Out

SC

–Out

Input Undervoltage

Input Overvoltage

Over Temperature

Module Faults

2-20ms typ.

Auto

Restart

5.7Vdc

(0-3mA)

50

Ω

SW2

SW3

1.23

Vdc

6K

1K

SW1

SW1, 2, & 3 shown

in "Fault" position

+Out

SC

–Out

+In

PC

PR

–In

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.

Primary Auxiliary Supply

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

Figure 3, PC powers a “green” module enabled LED.