Hi ,
One of my customer is using LM3526MX-L as replacement for MIC2026-2Y. ( Both parts are exactly P/P and active low enable) .
with MIC part circuit operation is fine. with LM3526 We are observing some glitch on FLTA which is causing the CPU to disable the USB Phy. This we are not seeing on the other vendor. Need to know why FLTA pin is going low when device is enabled .( TI and MIC device has same current limits. Device s not hitting current limit. )
Hi Ansel,
I think as per customer schematic output capacitor value is very high. This can generate large transient current when the switch is enabled and large values of capacitance at the output have to be rapidly charged. The in-rush currents created could exceed the short circuit current limit threshold of the device forcing it into the current limit mode. The capacitor is charged with the maximum available short circuit current set by the LM3526. The duration of the in-rush current depends on the size of the output capacitance and load current. Since this is not a valid fault condition, the LM3526 delays the generation of the fault flag for 1 ms.
This you can verify by removing 2 Nos of highlighted 220uf Capacitors.
There is a work around given in data sheet if you want to bypass such glitch at FLGA pin.
