Hey all,
We have noticed an issue in our LED light setup (see simple schematic snippet below). We have multiple of these IC's daisy chained together (10 IC's in total). We encounter issues with a very specific operating condition. This hardware is used to generate very short light flashes and that is achieved by switching on and off the +Vled with a MOSFET with a simple enable signal on the connector of this LED light system.
However, if we upload the brightness/pwm settings while VLED is disabled, then some IC's _sometimes_ do not register the requested settings apparently as we can see that some IC's do not drive the LED's on while the others work correctly. It's also changing from one test to the other, some IC's (other IC's) than the previous short flash would then not turn on the LEDs.
This situation does not happen when using higher PWM values than 3% or when using 100% PWM and a very low brightness instead.
We know how to avoid this situation but it would be interesting to have an explanation concerning the root cause. Of course, when you tell the device to start pulling very low currents through the LED which is not powered (VLED is off), then where does this current come from? Maybe that generates an illegal operating condition in the device? But why then? And why does it work with low brightness and high PWM?
Thanks for any valuable input or thoughts about the issue we see.
Gerrit
VLED Switch
LED Driver:
