Under rated Capacitor for current Backlight drive in RT1050-EVK

[Lorac]

#HardwareIssue 

Is your IMXRT1050-EVKB has broken when you plugged LCD on J8?

Mine yes, because the capacitor C88 is rated only 6.3V. It's a bad design. The design should support at least 25V in this case. The Backlight dc/dc converter can boot the BL+ voltage up to 24V when open circuit or during normal operating.

Brief, you must change this capacitor for at least 25V, I suggest 35V in this case.

[weidong_sun]

Hello Carol ,

    Thank you for kindly feedback and correction !

    I checked the datasheet of UM1661:

   Yes, right, C88's rating voltage , 35V is better choice.   So I quite agree with you!

[Comment] When will C88 be damaged?

       If LCD is not connected to J8, and power on board, UM1661's output voltage will be limited at 24V due to OVP, which will damage C88. So when LCD is not connected, CE pin can't be enabled.

       If LCD is connected to J8 at first, then power on board, UM1661's  output voltage will dropped to less than 6.3V due to LED array.

I'll feed this back to my superior technical department.

Thanks again!

Have a nice day!

NXP TIC Weidong Sun

[weidong_sun]

Just now I received information from AE team, new version of EVK has updated C88.

and for the 4.7uF capacitor, you can change it to be 1uF with 50V rated capacitor, which is enough.

Have a nice day!

BR,

Weidong