Other NXP ProductsのトピックPCA9955B Short Circuit Detection Issues

PCA9955B Short Circuit Detection Issues

ricola96 — Tue, 29 Aug 2023 13:24:52 GMT

Hello,

I've got a design that uses the PCA9955B and I'm having issues where there is a short circuit reported on all LEDs.

I measure the input pins of the driver and I'm reading ~3.4V but I noticed in the datasheet that if Vo >= Vth then the short circuit error happens. Vth is ~2.85V as per the datasheet.

I'm controlling my LEDs with 5V - is the intention that the LED is used to drop that 5V to something < 2.85V?

Thank you in advance.

Re: PCA9955B Short Circuit Detection Issues

ErikaC — Tue, 29 Aug 2023 19:43:56 GMT

Hello, could you please share your schematic?

Remember that for all unused LED outputs, the user must program their LED outputs to the ‘OFF’ state (LDRx = 00) and IREFx value to 00h, and all unused LED output pins must be pulled up to VDD with a recommended 100 k shared resistor.

Hope this helps.

Re: PCA9955B Short Circuit Detection Issues

ricola96 — Tue, 29 Aug 2023 20:36:34 GMT

Thank you for the response, please see attached for an image of the relevant part of my schematic.

I don't have the unused outputs tied to Vdd through that resistor - but would that be causing a short error in LEDs that are there?

I can add the LED in the coming days and keep you posted as well.