Dear Pololu team,
I am looking into using your U1V10F3 or U1V11F3 boards to power a wireless sensor node. Power supply will be a LiPo battery which does NOT have protection of its own. So I need some sort of voltage supervision to protect the LiPo from undervoltage.
Looking at the U1V10* and U1V11* modules, it’s not hard to guess they use the TPS61200 chip, which has a UVLO pin - which you sadly don’t make accessable, even if scraping off some solder protect from the U1V11* and making the required voltage divider is maybe possible with extreme care (probably only in my dreams).
So, instead, I put my hopes in the /SHDN pin of the U1V11* modules. Have you got any ideas for me what I could do to shut down power to VOUT when VIN drops below, say, 3.3 Volts?
Many thanks for any advice,
Looks like the whole board might be better if we just brought out the UVLO pin instead of the enable pin since it looks like the only cost of using the UVLO pin as a general shutdown pin is slightly higher current use in the disabled state. We’ll look into that and making a revision to the board.
For your case right now, I think the easiest thing to do would be to just access that IC pin on our board. You can see on the board that it’s tied to the VIN pin past the via on the component side and also through the via to the other side (yay, redundancy!). So you could cut around that via on the bottom side and between the via and the VIN pin on the component side and then you could access the UVLO pin of the chip at that via.
If you want some external circuit to use with the enable pin that is super low power and includes a comparator and fixed reference, you might consider some of the MCU supervisor chips: they’re made for various voltages and have various inversions and thresholds available. There might be some side effects, like a delay on power-up or after a glitch before the enable is reasserted (typically that would go to the reset pin of the MCU).