Application Notes

ATH Series of Wide-Output Adjust

Power Modules (12-V Input)

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Output On/Off Inhibit

For applications requiring output voltage on/off control,

each series of the ATH family incorporates an output

Inhibit control pin. The inhibit feature can be used wher-

ever there is a requirement for the output voltage from

the regulator to be turned off.

The power modules function normally when the Inhibit

pin is left open-circuit, providing a regulated output

respect to GND.

Figure 3-2 shows the typical application of the inhibit

The input is not compatible with TTL logic devices. An

open-collector (or open-drain) discrete transistor is rec-

ommended for control.

turned off, the module will execute a soft-start power-up

sequence. A regulated output voltage is produced within

20 msec. Figure 3-3 shows the typical rise in both the

output voltage and input current, following the turn-off

a 5-A constant current load.

Figure 3-2

Figure 3-3

Q1Vds (5 V/Div)

Vo (2 V/Div)

Iin (2 A/Div)

HORIZ SCALE: 10 ms/Div

PTH12060W

V

IN

1

10

4

5

6

2

3

L

O

A

D

C

IN

560 µF

C

OUT

330 µF

1 =Inhibit

GND

GND

V

OUT

9

V

8

Q

1

BSS138

R

SET

2.0k

Ω

1 %

0.1 W

7

Remote Sense

The ATH10 (10A), ATH12/15 (12/15A), ATH18/22 (18/

22A), and ATH26/30 (26/30A) products incorporate an

dard application). A remote sense improves the load

regulation performance of the module by allowing it to

compensate for any ‘IR’ voltage drop between itself and the

load. An IR drop is caused by the high output current

flowing through the small amount of pin and trace resis-

tance. Use of the remote sense is optional. If not used,

low-value resistor (15-

Ω or less) is connected between

mains in regulation.

With the sense pin connected, the difference between

amount of IR drop being compensated by the regulator.

This should be limited to a maximum of 0.3 V.

Note: The remote sense feature is not designed to compensate

for the forward drop of non-linear or frequency dependent

components that may be placed in series with the converter

output. Examples include OR-ing diodes, filter inductors,

ferrite beads, and fuses. When these components are enclosed

by the remote sense connection they are effectively placed

inside the regulation control loop, which can adversely affect

the stability of the regulator.

Over-Temperature Protection (OTP)

The ATH18/22 (18/22A) and ATH26/30 (26/30A) series of

products have over-temperature protection. These prod-

ucts have an on-board temperature sensor that protects

the module’s internal circuitry against excessively high

temperatures. A rise in the internal temperature may be

the result of a drop in airflow, or a high ambient tem-

perature. If the internal temperature exceeds the OTP

threshold, the module’s Inhibit control is automatically

pulled low. This turns the output off. The output voltage

will drop as the external output capacitors are discharged

by the load circuit. The recovery is automatic, and be-

gins with a soft-start power up. It occurs when the the

sensed temperature decreases by about 10 °C below the

trip point.

Note: The over-temperature protection is a last resort mecha-

nism to prevent thermal stress to the regulator. Operation at

or close to the thermal shutdown temperature is not recom-

mended and will reduce the long-term reliability of the module.

Always operate the regulator within the specified Safe Operating

Area (SOA) limits for the worst-case conditions of ambient

temperature and airflow.

ATH10K12