Disable DV24VxxF5 pull-ups on ENABLE pin?

[pcdangio]

Hello. I have a platform that uses both a DV24V22F5 and a DV24V50F5 step down regulator to drop a common 12V input down to two separate 5V rails. I have a single 5V arduino digital output controlling the enable pins on each regulator.

By default, I want the regulators to start up in disable mode. Normally, I could just use a pull-down resistor to do this while the arduino digital output floats during initial boot. However, the regulators have an internal 100K pull-up resistor that is basically overpowering the 10K pull-down i’ve added.

I did the math and I’d need at least a 1.9M Ohm pull-down to overpower the regulator’s internal 100K pull-up resistor (@ 12V Vin) and drive the enable pin below 0.6V (as required in documentation). Rather than doing this, I was wondering if there is a way to disable/remove the pull-up resistor.

So, is there a way to disable the pull-up? If not, can I just cut the trace from the pull-up resistor to Vin? Can I remove the resistor entirely? Can anybody point me to which resistor on the boards is the pull-up?

Thanks so much!

[BrandonM]

Hello.

It looks like you miscalculated the pull-down resistor value needed. For the D24V22F5 regulator, there is a 270k pull-up and the pin needs to be pulled to under 1V, so a 10k pull-down should be easily enough there. The D24V50F5 has a 100k pull-up and needs to be under 0.6V, so a 4.7k pull-down should work.

You can also remove the pull-up resistor from each board and add your own external pull-down like you mentioned. The pull-up resistor for the enable pin on each of those boards is the closest resistor to the EN pin on the underside of the board (opposite the silkscreen). Here are some pictures indicating the locations:

D24V22F5 regulator (item #2858):

D24V50F5 regulator (item #2851):

Brandon