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Over-Current Protection

Over-Temperature Protection (OTP)

Output On/Off Inhibit

PTH12060W

1

10

4

5

6

2

3

1 =Inhibit

GND

9

8

7

L

O

A

D

GND

330 mF

2 kW

1%

0.1 W

BSS138

560 mF

PTH12020W/L

SLTS208E–MAY 2003–REVISED OCTOBER 2005

For protection against load faults, all modules incorporate output over-current protection. Applying a load that

exceeds the regulator's over-current threshold will cause the regulated output to shut down. Following shutdown

a module will periodically attempt to recover by initiating a soft-start power-up. This is described as a hiccup

mode of operation, whereby the module continues in a cycle of successive shutdown and power up until the load

fault is removed. During this period, the average current flowing into the fault is significantly reduced. Once the

fault is removed, the module automatically recovers and returns to normal operation.

The PTH12020W and PTH12030W products have overtemperature protection. These products 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 temperature. If the internal

temperature exceeds the OTP threshold, the module's Inhibit control is internally 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 begins 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 mechanism to prevent thermal stress to the regulator.

Operation at or close to the thermal shutdown temperature is not recommended 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.

For applications requiring output voltage on/off control, each series of the PTH family incorporates an output

Inhibit control pin. The inhibit feature can be used wherever 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

has its own internal pull-up to a potential of 5 V to 13.2 V (see footnotes to specification table). The input is not

compatible with TTL logic devices. An open-collector (or open-drain) discrete transistor is recommended for

control.

Figure 14. Inhibit Control Circuit

turned off, the module will execute a soft-start power-up sequence. A regulated output voltage is produced within

constant current load.

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