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TIDA-03027: Reagrding buck LM3489 function of TIDA-03027

Yue Ma2
Prodigy 30 points

Part Number: TIDA-03027

Hello Sir/Madam

I wander why design need a buck IC LM3489? Charger can provide almost all voltage and current if 83B DFP negotiate with charger through CC line. LM3489 would lower efficiency of charging system.

Thanks and Best regards

Mayue 

  • 0
    TI__Expert 5130 points

    Yue, hello and thank you for your interest in Texas Instruments.  Your inquiry has been forwarded to the design team that owns the TIDA-03027 design. Please allow us 1-2 business days to respond to this and your other E2E question regarding this design. 

    Best Regards,

    J. Fullilove

    Texas Instruments

  • 0 in reply to JohnFullilove
    TI__Mastermind 30000 points

    Hello Sue,

    The reason why the LM3489 is used is for when there is a mismatch in power contracts between a USB Type-C host and charger. The LM3489 has the ability to "pass through" the source voltage in the event that the source voltage is equivalent to what is required for sinking. However, if the host requests only 9V, then the 83B would control the LM3489 to buck down the received 20V to only 9V.