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ATW28XXD Series

Connecting the inhibit input (Pin 8) to input common (Pin 10)

will cause the converter to shut down. It is recommended

that the inhibit pin be driven by an open collector device

capable of sinking at least 400µA of current. The open

circuit voltage of the inhibit input is 11.5 ±1.0VDC.

Block Diagram

Application Information

Inhibit Function (Enable)

EMI Filter

An optional external EMI filter (AFC461) is available that will

reduce the input ripple current to levels below the limits

imposed by MIL-STD-461B CEO3.

Device Synchronization

To take advantage of this capability, the system designer

must assign one of the converters as the master. Then, by

definition, the remaining converters become slaves and will

operate at the masters’ switching frequency.

The user should be aware that the synchronization

system is fail-safe; that is, the slaves will continue

operating should the master frequency be interrupted for

any reason. The layout must be such that the synchronization

output (pin 2) of the master device is connected to the

synchronization input (pin 2) of each slave device. It is

advisable to keep this run short to minimize the possibility

of radiating the 250KHz switching frequency.

The appropriate parts must be ordered to utilize this

feature. After selecting the converters required for the

system, a ‘MSTR’ suffix is added for the master converter

part number and a ‘SLV’ suffix is added for slave part

number. See Part Number section.

Typical Synchronization Connection

Whenever multiple DC/DC converters are utilized in a single

system, significant low frequency noise may be generated

due to the slight differences in the switching frequencies of

the converters (beat frequency noise). Because of the low

frequency nature of this noise (typically less than 10KHz), it

is difficult to filter out and may interfere with proper operation

of sensitive systems (communications, radar or telemetry).

International Rectifie roffers an option,which allows

synchronization of multiple AHE/ATW type converters, thus

eliminating this type of noise.

ATW28xxD

ATW28xxS

AFC461

or

AFV461

ATW28xxD

or Other

Compatable

+ In

+ In

+ In

Case

Case

Case

Return

Return

Return

Return

Return

Return

Output

Output

Output

MSTR

SLV

SLV

+ In

Return

Output

Return

System

Bus

Output

Output

3

4

+Vout

Output

Return

Pulse Width

Modulator

EMI

Filter

1

8

10

+Input

Enable

Input

Return

FB

Drive 1

Drive 2

2

Sync

Error Amp

& Reference

5 -Vout