SHORT

ILIMx

48000

I

R

=

TPS2540, TPS2540A

TPS2541, TPS2541A

www.ti.com

SLVSAG2C

– OCTOBER 2010 – REVISED OCTOBER 2011

Current-Limit Thresholds

The TPS2540/40A/41/41A has two independent current-limit thresholds that are each programmed externally

with a resistor. The following equation programs the typical current-limit threshold:

(3)

RILIM1 when ILIM_SEL is logic HI. The ILIM_SEL pin allows the system to digitally select between two

current-limit thresholds, which is useful in end equipment that may require a lower setting when powered from

batteries vs. wall adapters.

FAULT Response

The FAULT open-drain output is asserted (active low) during an over-temperature or current limit condition. The

output remains asserted until the fault condition is removed. The TPS2540/40A/41/41A is designed to eliminate

false FAULT reporting by using an internal deglitch circuit for current limit conditions without the need for external

circuitry. This ensures that FAULT is not accidentally asserted due to normal operation such as starting into a

heavy capacitive load. Over-temperature conditions are not deglitched and assert the FAULT signal immediately.

Undervoltage Lockout (UVLO)

The undervoltage lockout (UVLO) circuit disables the power switch until the input voltage reaches the UVLO

turn-on threshold. Built-in hysteresis prevents unwanted oscillations on the output due to input voltage drop from

large current surges.

Thermal Sense

The TPS2540/40A/41/41A protects itself with two independent thermal sensing circuits that monitor the operating

temperature of the power distribution switch and disables operation if the temperature exceeds recommended

operating conditions. The device operates in constant-current mode during an over-current condition, which

increases the voltage drop across power switch. The power dissipation in the package is proportional to the

voltage drop across the power switch, so the junction temperature rises during an over-current condition. The

first thermal sensor turns off the power switch when the die temperature exceeds 135

°C and the part is in current

limit. The second thermal sensor turns off the power switch when the die temperature exceeds 155

°C regardless

of whether the power switch is in current limit. Hysteresis is built into both thermal sensors, and the switch turns

on after the device has cooled by approximately 10

°C. The switch continues to cycle off and on until the fault is

removed. The open-drain false reporting output FAULT is asserted (active low) during an over-temperature

shutdown condition.

Copyright

© 2010–2011, Texas Instruments Incorporated

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Product Folder Link(s): TPS2540, TPS2540A TPS2541, TPS2541A