PCF1545 PWM Dimming Behavior Analysis on Embedded Boards

[jeremiranner]

I have been testing PWM dimming behavior with the PCF1545 on a small embedded LED control board and noticed some interesting behavior at lower brightness levels.

The setup currently uses:

• MCU: Cortex-M based controller
• Communication: I2C
• LED load: multi-segment indicator array
• Supply voltage: 3.3V

At higher PWM duty cycles, brightness transitions appear smooth and stable. However, when reducing brightness below roughly 15–20%, slight flickering becomes visible depending on the LED type and refresh timing.

A few observations so far:

• Increasing the PWM refresh frequency reduced visible flicker.
• Different LED colors behaved differently, especially blue LEDs.
• Timing jitter from other RTOS tasks slightly affected consistency.
• Power rail noise also influenced low-brightness stability.

I am currently experimenting with:

• adjusting scan/update intervals
• optimizing I2C transaction timing
• using separate power filtering for the LED section
• synchronizing PWM updates with the main refresh loop

Has anyone else analyzed PWM dimming characteristics on the PCF1545 in embedded applications?

I would be interested in:

• recommended PWM frequency ranges
• best practices for low-brightness stability
• techniques to reduce flicker during dynamic updates
• observations when using RTOS environments vs bare-metal systems

Any practical insights or scope captures would be greatly appreciated.