Hello,
I am using a S18V20F12 board to boost a 4.2V battery to 12v. The enable pin is activated with a 5.2V signal from a microcontroller. Normal function is for 5.2V to be sent for 30 seconds, and then it goes low. This all works fine in an isolated circuit, however when I introduce the S18V20F12, there seems to be voltage “backfeed” of 2.7 V between EN and GND, so that the EN pin is never pulled low. When I remove the enable pin wiring from the circuit, the 2.7V is no longer present.
Is there anything I’m obviously doing wrong here?
I just worked out that the pin isnt “driven low” ,power is just cut (not to the main system, just the enable pin)…would this cause a floating state and issues? Im proposing to instead use thr 5v signal pulse to trigger an arduino nano or similar to handle enabling the regulator
The S18V20F12 regulator uses a 100 kΩ pull-up resistor on the board to connect the ENABLE pin to reverse-protected VIN. It should be easy for a microcontroller to drive that pin low, but in your case it sounds like your pin can only switch between a high state and a floating state, which explains why connecting it directly will not work.
Using an Arduino pin to handle the ENABLE pin instead would work. A simpler solution that could allow you to keep using the same microcontroller would be to add a stronger pull-down resistor (e.g. 1kΩ) between the ENABLE pin and ground. That would change its default state from high (enabling the board) to low (disabling the board), and applying the 5.2 volt signal from your pin would switch the state.
