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TPS92520-Q1: About TPS92520 output capacitor value problem

zhang lin
Intellectual 310 points
Part Number: TPS92520-Q1

Tool/software:

Hello, expert.

I encountered a problem when using tps92520. I changed the output capacitance of TPS92520 from 1UF to 4.7UF when rectifying EMC.

My current application is just a string of LED, current 800mA, PWM dimming will be used, dimming frequency is 215hz,LED series connection will only turn on and off at the same time. I looked at the manual and wrote that the value of capacitance should be paid attention to in the application of pixel beam or matrix LED load.

Please help me check whether there is any risk in the change of capacitance or what problems should be paid attention.

  • +1
    TI__Mastermind 23096 points

    Hello Zhang,

    Generally speaking having too much output capacitance can cause issues with shunt fet dimming seen in Matrix managers (LMM).  The fast transient due to shunt fet dimming can ring with cable harness and cause problems.  If you are doing just PWM dimming then you should be ok, but keep in mind that part of the output current goos into changing the output capacitance and that is taken away (delays) from turning on the LEDs.  That means at low duty cycle the linearity might not be as good.  You can reduce output noise on output by selecting different inductance and using ferrite beads with small filter capacitor instead of large output capacitance.  

    -fhoude