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Overcurrent Protection (OCP)

Overtemperature Protection (OTP)

Auto-Track™ Function

PTV03020W

SLTS243A – FEBRUARY 2005 – REVISED OCTOBER 2007

Figure 10. Inhibit Waveform

For protection against load faults, the modules incorporate output overcurrent protection. Applying a load that

exceeds the overcurrent threshold causes the regulated output to shut down. Following shutdown, a module

periodically attempts to recover by initiating a soft-start power up. This is described as a hiccup mode of

operation, whereby the module continues in the 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.

An onboard temperature sensor protects the module 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 Inhibit control is internally pulled low. This turns the

output off. The output voltage drops 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 sensed temperature decreases

by about 10C below the trip point.

Note: The overtemperature 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 reduces 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.

The Auto-Track function is unique to the PTH/PTV family, and is available with all POLA products. Auto-Track

was designed to simplify the amount of circuitry required to make the output voltage from each module power up

and power down in sequence. The sequencing of two or more supply voltages during power up is a common

requirement for complex mixed-signal applications that use dual-voltage VLSI ICs such as the TMS320™ DSP

family, microprocessors, and ASICs.

How Auto-Track™ Works

Auto-Track works by forcing the module output voltage to follow a voltage presented at the Track control pin

(1)

This control range is limited to between 0 V and the module set-point voltage. Once the track-pin voltage is

raised above the set-point voltage, the module output remains at its set-point

(2)

. As an example, if the Track pin

of a 2.5-V regulator is at 1 V, the regulated output is 1 V. If the voltage at the Track pin rises to 3 V, the regulated

output does not go higher than 2.5 V.

Under Auto-Track control, the regulated output from the module follows the voltage at its Track pin on a

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