TPS2521 datasheet(22/47 Pages) TI

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The internal fast-trip comparator employs a scalable threshold (ISC) which is equal to 2 × ILIM. This enables the

user to adjust the fast-trip threshold rather than using a fixed threshold which can be too high for some low

current systems. The device also employs a fixed fast-trip threshold (IFT) to protect fast protection against hard

short-circuits during steady state. The fixed fast-trip threshold is higher than the maximum recommended user

adjustable scalable fast-trip threshold. Once the current exceeds ISC or IFT, the HFET is turned off completely

within tFT. Thereafter, the devices tries to turn the HFET back ON after a short de-glitch interval (30 μs) in a

current limited manner instead of a dVdt limited manner. This ensures that the HFET has a faster recovery after

a transient overcurrent event and minimizes the output voltage droop. However, if the fault is persistent, the

device will stay in current limit causing the junction temperature to rise and eventually enter thermal shutdown.

See Overtemperature Protection (OTP) section for details on the device response to overtemperature.

IOUT

ILIM

Time

OUT

VIN

TSD

TSDHYS

tRST

Thermal Shutdown

2 x ILIM

Transient Severe Overcurrent

Persistent Severe Overcurrent

Retry Timer Elapsed

(1)

Overcurrent Removed

tSC

Current Limited

Start-up

dVdt Limited

Start-up

VPG

(1) Applicable only for TPS25210A variant

tRST

Thermal Shutdown

Retry Timer Elapsed

(1)

Short-circuit Removed

tFT

dVdt Limited

Start-up

IFT

Output Hard Short-circuit to ground

tPGD

VIN

Figure 8-4. TPS2521xx Short-Circuit Response

8.3.5 Analog Load Current Monitor

The device allows the system to accurately monitor the output load current by providing an analog current sense

output on the ILM pin which is proportional to the current through the FET. The user can sense the voltage (VILM)

across the RILM to get a measure of the output load current.

IOUT (A) =

VILM (µV)

RILM :À; x GIMON (µA/A)

(6)

The waveform below shows the ILM signal response to a load step at the output.

TPS2521

SLVSFX8 – MARCH 2021

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