STP16CPC26 flash on power up

[GlassPaul]

Hi! I'm using the STP16CPC26 as an LED driver, but have a problem where all the attached LEDs initially flash when powering up. This is a problem since this is a UI with a large-ish number of LEDs and you get hit right in the face with the bright flash.

I've tried delaying /OE until after I've written all zeros, and I've tried delaying applying power (12V) to the LEDs until after all zeros and /OE, but without a complete solution. Delaying the 12V power helps, but there is always a tiny blink regardless of what I do.

Is there some way to ensure that everything is dark on power-up?

Paul

[Anna180]

Hi Paul — the flash occurs because the STP16CPC26 outputs are undefined at power-up. To fix it, hold /OE high (outputs off) with a pull-up until your MCU has initialized and written zeros, then enable it. Also add pull-resistors on data, clock, and latch lines to prevent random input states. If available, use CLEAR/RESET to force outputs low, or delay the 12 V LED power with a MOSFET until setup is complete. These hardware tweaks ensure all LEDs stay dark during startup.