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5

AMF28XXD Series

AMF28XXD Block Diagram

Application Information

Inhibit Function

EMI Filter

Device Synchronization

Notes to Specifications

An optional EMI filter is available (AFH461) that will

reduce the input ripple current to levels below the

limits imposed by MIL-STD-461 CE03.

When multiple DC/DC converters are utilized in a

single system, significant low frequency noise may

be generated due to a small difference in the switch-

ing frequency of the converters (beat frequency

noise). Because of the low frequency nature of this

noise (typically less than 10 KHz), it is difficult to

filter out and may interfere with proper operation of

sensitive systems (communication, radar or telem-

etry). Advanced Analog provides synchronization

of multiple AMF type converters to match switching

frequency of the converter to the frequency of the

system clock, thus eliminating this type of noise.

3

4

+ V out

Re tu rn

P u ls e W idth

M odulato r

Prim a ry

H ouseke epin g

S upply

EM I

Filte r

8

1

2

7

+ In put

E nable

S y nc

In put

Re tu rn

FB

CS

Drive

5

-V o u t

6

Ca s e

E rro r

A m p &

R e f

Connecting the enable input (Pin 1) to input common

(Pin 7) will cause the converter to shut down. It is

recommended that the enable pin be driven by an

open collector device capable of sinking at least 400

µA of current. If the user chooses not to use the inhibit

function, it may be left open and the converter will

function normally. Because it is internally pulled up,

the open circuit voltage of the inhibit input is 10.0

+1V

DC.

1.

Applicable to positive and negative outputs.

2.

Maximum combined output is 12 watts. 10.8 watts (max.) is available from either output (90%).

3.

4.

1.2 watt load on output under test, 1.2 watt to 10.8 watt load change on other output.

5.

Capacitive value may be any value from 0 to the maximum limit without compromising DC performance. A

capacitive load in excess of the maximum limit will not disturb loop stability but may interfere with the operation

of the load fault detection circuitry, appearing as a short circuit during turn-on.

6.

Parameter shall be tested as part of design characterization and after design or process changes. Thereafter,

parameters shall be guaranteed to the limit specified.

7.

Load step transition time between 2 and 10 microseconds.

8.

50% load.

9.

Input step transient time between 1 and 10 microseconds.

10. Turn-on delay time measurement is for either a step application of power at the input or the removal of a ground

signal from the inhibit pin while power is applied to the input.