TPS92641：TPS92641:模拟调光驱动波形异常。

Hi pengcheng,

For question 1, the datasheet should contain enough information for you to do the design. If possible, please send a clearer version of your schematic to me (maybe through e-mail) and I can help with schematic review.

For question 2, please check if BOOT UVLO happens (Please refer to Section 7.3.13 Boot Undervoltage Lockout (UVLO) from the datasheet).

Best Regards,

Steven

Hi pengcheng,

If the cause is BOOT UVLO, then you can consider enlarging the capacitance of the BOOT capacitor or changing the switching MOSFETs to those with lower Qg and see if it helps.

Best Regards,

Steven

Hi pengcheng,

I take a quick look over your schematic. The D25 diode is in the wrong polarity.

There are several things to check - 

• Have you ever tried CSD18563Q5A? If so, how about the results?
• What is the status of Q18 and Q17 during your test? Normally, when the shunt FET is used, it is not recommended to use large output capacitance as you do in your schematic.
• It would be better if you can summarize all the current findings in a file and mark the signals in the oscilloscope capture / mark the measurement points in the schematics to make it easier for me to take a look on. Thanks.

Best Regards,

Steven