LEDx output signal for PCA9955

[tomofumiyasuda]

Hi All,

I control LED driver (PCA9955B) using i.MX RT1064. After I set each register and LED1 pin is output. However waveform from LED1 pin is negative voltage(-0.24V). The power supply of PCA9955B is 3.3V. What are the possible causes of this phenomenon? It is unknown whether software or hardware.

<PCA9955B data sheet>

https://www.nxp.com/docs/en/data-sheet/PCA9955B.pdf 

[tomofumiyasuda]

Hi Jose,

Thank you for your reply. 

The cause was hardware. I'm sorry to have caused you trouble.

Best regards,

[reyes]

Hi,

Can you please share your schematics for a review?

Thanks

Jose

[reyes]

Hi,

When you mentioned ‘waveform from LED1 pin is negative voltage(-0.24V)’, is this a negative spike or the voltage maintains at this level all the time?

I could use waveforms and schematics for a review.

Thanks

Jose