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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 cir-

cuit voltage of the inhibit input is 11.5 ±1 VDC.

ATW28XXD Block Diagram

Application Information

Inhibit Function

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 sys-

tem is fail-safe; that is, the slaves will continue operating

should the master frequency be interrupted for any rea-

son. 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 possibil-

ity of radiating the 250KHz switching frequency.

The appropriate parts must be ordered to utilize this fea-

ture. After selecting the converters required for the sys-

tem, 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).

Advanced Analog offers an option, which allows synchroni-

zation of multiple AHE/ATW type converters, thus eliminat-

ing this type of noise.

A T W 28xxD

A T W 28xxS

A F C 461

or

AF V 4 6 1

A T W 28xxD

or O ther

C o m patab le

+ In

+ In

+ In

Ca se

Ca se

Ca se

Re turn

Re turn

Re turn

Re turn

Re turn

Re turn

Ou tp ut

Ou tp ut

Ou tp ut

MS T R

SLV

SLV

+ In

Re turn

Ou tp ut

Re turn

Sy ste m

Bu s

Ou tp ut

Ou tp ut

3

4

+ V out

Re tu rn

P u ls e W idth

M o d u la to r

EM I

Filte r

1

8

10

+ In put

E nable

In put

Re tu rn

FB

Drive 1

Drive 2

2

S y nc

E rror A m p

& R eference

5 -V out