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Power-Up Characteristics

(5 V/div)

(2 V/div)

(2 A/div)

t − Time − 4 ms/div

Overcurrent Protection

PTR08100W

SLTS284B – AUGUST 2007 – REVISED DECEMBER 2007

When configured per the standard application, the PTR08100W power module produces a regulated output

voltage following the application of a valid input source voltage. During power up, internal soft-start circuitry slows

the rate that the output voltage rises, thereby limiting the amount of in-rush current that can be drawn from the

input source. The soft-start circuitry introduces a short time delay (typically 10 ms) into the power-up

characteristic. This is from the point that a valid input source is recognized. Figure 13 shows the power-up

waveforms for a PTR08100W, operating from a 12-V input and with the output voltage adjusted to 3.3 V. The

waveforms were measured with a 6-A constant current load.

Figure 13. Power-Up Waveforms

For protection against load faults, the PTR08100W incorporates output overcurrent protection. Applying a load

that exceeds the regulator's overcurrent threshold causes the regulated output to shut down. Following

shutdown, the 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.

Copyright © 2007, Texas Instruments Incorporated

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Product Folder Link(s): PTR08100W