The TPS12000-Q1 feature adjustable short circuit protection. The threshold and the response time can be adjusted using ISCP resistor and TMR capacitor respectively. The device senses the voltage across the CS+ and CS– pins. These pins can be connected across an external current sense resistor or across the FET drain and source terminals for FET RDSON sensing. Set the circuit breaker detection threshold using an external resistor R_ISCP across ISCP and GND. Use Equation 6 to calculate the required R_ISCP value.

Equation 6.

Where, R_SNS is the current sense resistor value or the FET RDSON value, I_SC is the short circuit current level. The short circuit protection response is fastest < 6 µs with no C_TMR cap connected across TMR and GND pins.

In the configurations of high side current sense with CS_SEL connected to GND, during Q1 turn ON, first the FET’s VGS is sensed by monitoring the voltage across PD to SRC. Once VGS raises above G1_GOOD threshold to ensure that the external FET gate is enhanced, then the SCP comparator output is monitored. If the sensed voltage across CS+ and CS– exceeds the ISCP set point, PD pulls low to SRC and FLT asserts low within 6μs (with TMR open). Subsequent events can be set either to be auto-retry or latch off as described in following sections

With CS_SEL connected to >2V i.e low side current sense configurations, the device does not wait for the FETs to enhance (doesnot wait for G1_GOOD threshold to reach) and directly looks at the SCP comparator output to pull PD to SRC in the case of a short circuit event.