Other Parts Discussed in Thread: TPS82130, LMZ10503, LMZ30604, LMZ30606
We are using the LMZ20502SILT and on 4 of our boards the part "goes bad" after a few power cycles. The failure mode is a very low ohm reading to ground at the VOUT pin and the voltage is stuck around 0.5V.
This mode is consistent with all 4 failures. The output is supposed to be 1.35V. Rtop is 69.8K, Rbot is 56.0K and the cap across Rtop is 56pF. Cin is 47uF/10V and Vin is 3.3V. Cout is pretty high at 825uF and the rail is prebiased at startup. On top of that my enable pin is controlled by a buffer that has no power for about 10mS when the 3.3V is applied. I suspect the output capacitance is way too high. I have 4 failures out of 20 boards. This is a ASIC application which is driving the Cout qty. I might be able to remove some of the Cout and I added a pull down resistor on the enable pin. What is my Cout limit? Is there a better part for the job?