max gpio current for nRF52

RE: max gpio current for nRF52

Al Bundy — Wed, 07 Mar 2018 10:32:05 GMT

Ole Bauck

Can you please answer questions 2, 3, 4, 5?

RE: max gpio current for nRF52

Craig — Thu, 01 Jun 2017 19:40:48 GMT

Use a LP5562 I2C device....works wonders for this LED which I am using as well......

RE: max gpio current for nRF52

Luis — Fri, 15 Apr 2016 10:17:03 GMT

I also usually use MOSFETs for leds, but I am studying the option to remove them. Things I don't like about having mosfets for my rgb led:

Each mosfet needs 2 extra resistors, one to limit the gate current and one to make sure the mosfet will be off (for example) even if the gate pin is in undefined behaviour.
If you dont limit the gate current with "big" resistor, instant charge currents can get quite high, and this gets important if you are switching the led at some high frequency or doing PWM on the gate to change luminosity.
To use a RGB led means to use 3 mosfets + 6 resistors... so part counting goes up, also pricing and pcb area.

Of course it has its benefits, like being able to use higher current leds.

I may try to find smaller package with maybe 3 or several mosfets inside... I need my small rgb led to be visible at day ligth from a distance of a pair of meters... So not sure what option I will be following yet.

RE: max gpio current for nRF52

RK — Fri, 15 Apr 2016 00:13:49 GMT

I drive all LEDs via MOSFETs so I don't need to worry about sourcing/sinking too much current from the nRF chips. Low voltage logic MOSFETs are available cheaply, in pairs if you like. You can have LEDs as bright as you like and and have as many of them on at the same time as pleases you.

RE: max gpio current for nRF52

Luis — Thu, 14 Apr 2016 09:18:41 GMT

Thank you for the recommendation. That led does not seem bright enough, its datasheet says 20-40 mcd at 2mA, while mine (CLMVC-FKA) says 30-140 mcd minimum at 5mA. I will anyway explore this option of changing to a lower power LED and use nRF52 sinking instead of sourcing current.

RE: max gpio current for nRF52

IvanD — Thu, 14 Apr 2016 08:50:42 GMT

Make a look on the LED: SML-LX0404SIUPGUSB It is a very bright one and maybe you could save current a little bit.

RE: max gpio current for nRF52

Ole Bauck — Fri, 18 Mar 2016 10:23:47 GMT

Going a bit over 15mA will probably be ok. This is a recommended number as the real number will depend on alot of things specific for each pcb design. If you sink 15mA you should be able to source N mosfet gates (if this requires low current).

RE: max gpio current for nRF52

Luis — Thu, 17 Mar 2016 16:44:32 GMT

One more question, if I combine sink and source pins, is it safe to go a bit higher than 15mA suming sink+source? For example sink RGB leds and source N mosfet gates.

RE: max gpio current for nRF52

Luis — Thu, 17 Mar 2016 16:37:11 GMT

Thank you for the answer. Is that a real specification or still something that has to be tested and 15mA is to make sure we are on the safe side? I find it quite low. :( For example in my case I have a very low power RGB led, 5mA each led. If it goes full on it is already 15mA, so it could be risky to even charge N mosfet gates using other gpio pins at the same time?

RE: max gpio current for nRF52

Ole Bauck — Thu, 17 Mar 2016 16:15:03 GMT

We recommend 15mA total current sink/source on the chip for normal operation. This can be on one pin if you want (different than nRF51). We recommend that you sink current rather than source current because of more ground pads than vdd pads.