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TPS92692-Q1: Over current protection unwanted triggered

Gary Jiang
Intellectual 980 points
Part Number: TPS92692-Q1

Hi team,

My customer now uses TPS92692-Q1 in their headlight product, LED current is 1A, and they want to use hiccup mode, so they connect FLT pin to SS pin.

They find that when the high beam light switches to low beam light(using MOSFET to bypass several LEDs), the LED current will ramp up to 2A for 600 us and trigger LED string over current protection, enter into hiccup mode, causing the low beam light blink.

So I want to ask is there any solution we can solve this issue? Like adding LED string overcurrent response time to blank this unwanted 600us high current? Or add a 100ohm+1uF RC low pass differential filter between CSP and CSN, is this solution valid?

Thank you.

Best regards,

Gary 

  • 0
    TI__Genius 17690 points

    Hi Gary,

    In general, when you are using a MOSFET to shunt the high beam to go to low beam you need that shunt FET to turn on and off slowly so it does not cause the over current that you are seeing. 

    If you filter the CSP and CSN pin like you mentioned then you will add phase lag to the control loop and the loop will have compensated to low BW.  This method will have lower rejection BW along with the current in low beam that will go to 2A still and it's not the prefer method.

    Thanks Tuan