Other Parts Discussed in Thread: TPS54202
I'm trying to substitute the TPS54202H in for the TPS54202 since the TPS54202 is impossible to find.
I'm using the EN/UV pin to protect the battery from over discharge. I'm using an R4 of 668k and an R5 of 95.3k. All my calculations and a spice simulation say that the enable and disable voltages should be 10.17V and 11.12V respectively. However, I'm getting consistently 10.4V and 11.34V, which seems to point to an extra ~4Meg if impedance to ground on the EN node. I've built up two samples and both do it even after swapping out the parts. I've measured the blank PCB resistance to ground an it is VERY high impedance with no parts populated. Resistors are all 1% and I measured them before populating. So it has to be the TPS54202H.
This is starting to make me question the specifications of the device or the calculations in the datasheet don't reflect what the part actually does. I never had issues with TPS54202 performance not matching the calculations. I question the Rpd value inside the TPS54202H. My limited experience is that resistors are difficult to grow in silicon and accuracy can widely vary if they are not trimmed. Maybe this is why?
