I have a design wherein the basic idea is to control individual LED strings and dim (analog dimming) them using Pi Pico via I2C interface.
This board is the LED driver which will be connected to the LED array board where the strings of LED are populated.
The LED driver is a constant current one, one is Recom and another one is from Diodes Inc.
More detailed info can be found in the attached schematic.
Parts Datasheet Links -
- RCD-24-0.35/VREF - Constant Current LED Driver
- TBD62786AFWG,EL, Application note - High Side Load Switch
- AD5142AWBCPZ10-RL7 - Digital potentiometer
- PCAL6408APWJ - I2C Expander
Recom's datasheet says "Don't connect the V- output to Gnd"
I had assigned a separate net to it (provided jumpers for flexibility of using two different drivers.)
I have connected the high side switch according to the datasheet and app note, but to control the load switch the gate or input pin of the load switch is being controlled by the I2C expander.
Where should I connect the I2C expander GND: GNDD or GND?
If I want to control the load switch I must connect the IO expander's ground to the GNDD net but that would mean for I2C it won't use the GND of Pi Pico.
Am I missing something here or is my schematic wrong? Please advise.
I found the following post useful.
If there's any shortcoming in the post understandability please let me know.