We are using the TPS62130 circuit for supplying four DCP020515D (external clocked) with +5.4V out of +12V computer power supply. The output is pre biased by a schottky diode from +5V of same computer power supply. This path is used for delivering the high startup current (>4A) of all DCP020515P. The TPS62130 will be delayed (10ms) enabled via RC circuit from external clock of DCP020515D and delivers the normal load current (<2A).
Generally it works, but up to 10% of TPS62130 did not start after an indefinite time. Reason: The soft start pin has low impedance (100Ohm-15kOhm), also if it is unsoldered and measured directly between soft start pin and GND. If we apply a 10k resistor between SS pin and output, most of the not working devices will start and are working normally!!! If so the power path is not damaged! The output draws no current, so internal switches are off if device is not working!
We made many tests with hot plug and unplug of input voltage, overloading, overheating (not soldered exposed pad), several 1000 start cycles but we cannot destroy it in that way! Not all devices are affected but it is not acceptable when 10% stops working after indefinite time!
What is going wrong here?
Startup behavior with 10ms delay:
CH1: Switching node of TPS62130
CH2: Output current via 51mOhm shunt (instead L60)