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5

AMF28XXS Series

AMF28XXS Block Diagram

Application Information

Inhibit Function

EMI Filter

Device Synchronization

Notes to Specifications

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. The open circuit voltage of the en-

able input is 10.0 +1 V

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

Return

P ulse W idth

M odulator

Prim ary

H ousekeeping

S upply

EM I

Filter

U nder-V oltage

Detec tor

8

1

2

7

+ Input

E nable

Sync

Input

Return

Error

Am p &

Ref

FB

CS

Driv e

6

Case

1 Parameter guaranteed by line and load regulation tests.

2 Bandwidth guaranteed by design. Tested for 20 Hz to 2 MHz.

3 Capacitive load 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.

4 Parameter shall be tested as part of design characterization and after design or process changes. Therefore this Parameters shall

be guaranteed to the limit specified.

5 Load step transition time between 2 and 10 microseconds.

6 Recovery time is measured from the initiation of the transient to where V

7 Input step transition time between 1 and 10 microseconds. Parameter guaranteed by design but not 100% tested.

8 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.