Part Number:TPS92691
Hi team,
I'm using TPS92691 in one of my designs. The input is 24V, the output is 48V @ 380mA. The LED string configuration is 6 parallel x 14 series with Vf=2.8V.
My circuit is very similar to Fig 24 in the datasheet. The PWM pin is set HIGH (digital dimming is disabled) via MCU and the IADJ pin is set via 4kHz PWM from the same MCU through a 10k/1uF RC circuit.
I am required to control the LED current for dimming levels down to 3.8-4.2mA. This is done during a calibration process where IADJ is adjusted while output current is measured. The PWM cycle that gives the LED current in the targeted range is then stored.
Most of my tests so far have been successful, but I'm encountering some issues. The LED current is >4.5mA once the driver is turned on and with the IADJ pin at 0V (duty cycle through the RC is 0%).
I believe this is due to the offset voltage of the current sense amplifier, where the devices that haven't been able to perform here are units with lower/negative offset. Does this sound right, or could there be something else to consider?
Thanks,
Brian