Unable to achieve dimming on LYT6067C

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Hi, We have used the LYT6067C for a dimmable LED Driver Circuit design. We have referenced the DER660 Application Note. We have been able to switch on the LED panel but unable to achieve dimming. We have followed the application note thoroughly but we have observed that the OP Amp LT1638 is not injecting any current across the FB path. We are applying PWM at 730Hz and is driving the PWM on a 5V duty cycle. Please help us resolve the issue.

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Hi homeone,

Thank you for using the newest product LYTSwitch-6 for your project.

May I know if op amp is supplied properly by the auxiliary supply V(aux) in the schematic? If no current injection is observed, op amp may possibly not functioning well due to lack of supply.

Current injection loop should also be slow enough to not trigger the feedback pin overload protection. You may increase the value of R14 to slow down the response.

For the layout suggestion, please make sure to place the dimming circuit close to IS pin and FB pin to prevent noise from disturbing the loop. I hope this helps.