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IOUT

ILIM

Time

OUT

VIN

ITIMER

TSD

tITIMER

Transient Overcurrent

ITIMER expired

Persistent Output Overload

Thermal shutdown

TSDHYS

Current limiting

operation

VPG

tLIM

PGTH

1.2 V

tPGD

ITIMER expired

Persistent Output Overload

Current limiting

operation

tLIM

tPGD

Overload Removed

tPGA

tITIMER

¨9ITIMER

2 x ILIM

VINT

Figure 8-3. TPS2521xx Active Current Limit Response

Note

1. Leave the ITIMER pin open to allow the part to limit the current with the minimum possible delay.

2. Shorting the ITIMER pin to ground results in minimum overcurrent response delay (similar

to ITIMER pin open condition), but increases the device current consumption. This is not a

recommended mode of operation.

3. Active current limiting based on RILM is active during startup. In case the startup current exceeds

ILIM, the device regulates the current to the set limit. However, during startup the current limit is

engaged without waiting for the ITIMER delay.

4. During overvoltage clamp condition, if an overcurrent event occurs, the current limit is engaged

without waiting for the ITIMER delay.

5. Increasing the CITIMER value extends the overcurrent blanking interval, but it also extends the

time needed for the CITIMER to recharge up to VINT. If the next overcurrent event occurs before

the CITIMER is recharged fully, it will take lesser time to discharge to the ITIMER expiry threshold,

thereby providing a shorter blanking interval than intended.

During active current limit, the output voltage will drop resulting in increased device power dissipation across the

HFET. If the device internal temperature (TJ) exceeds the thermal shutdown threshold (TSD), the HFET is turned

off. Once the part shuts down due to TSD fault, it would either stay latched off (TPS252x1L variant) or restart

automatically after a fixed delay (TPS2521xA variant). See Overtemperature Protection (OTP) for more details

on device response to overtemperature.

8.3.4.3 Short-Circuit Protection

During an output short-circuit event, the current through the device increases very rapidly. When a severe

overcurrent condition is detected, the device triggers a fast-trip response to limit the current to a safe level.

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TPS2521

SLVSFX8 – MARCH 2021

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