Remote Sense

Overcurrent Protection

Overtemperature Protection (OTP)

PTH12060W/L

www.ti.com .................................................................................................................................................... SLTS217H – MAY 2003 – REVISED DECEMBER 2008

Products with this feature incorporate an output voltage sense pin, VO Sense. A remote sense improves the load

regulation performance of the module by allowing it to compensate for any IR voltage drop between its output

and the load. An IR drop is caused by the high output current flowing through the small amount of pin and trace

resistance.

To use this feature simply connect the VO Sense pin to the VO node, close to the load circuit (see data sheet

standard application circuit). If a sense pin is left open-circuit, an internal low-value resistor (15-

Ω or less)

connected between the pin and the output node, ensures the output remains in regulation.

With the sense pin connected, the difference between the voltage measured directly between the VO and GND

pins, and that measured from VO Sense to GND, is the 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 nonlinear 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.

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

exceeds the regulator's 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 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 PTH12020, PTV12020, and PTH12030 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 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 10°C 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 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.

Copyright © 2003–2008, Texas Instruments Incorporated

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