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TPS2116: VIN2 and VOUT short ?

user244678
Expert 1245 points
Part Number: TPS2116

Hello,

In the circuit below, I switch between the 5V input of VIN1 and the USB VBUS of VIN2.
The operating mode is priority mode.
I am currently experiencing the following symptoms.
1. When VIN1=5V input and VIN2=floating, the same voltage as VOUT appears at VIN2.
    At this time, the 5V current of VIN1 is 1A.
2. Next, when VIN1=5V input, VIN2=USB VBUS 5Vinput, the current consumption of VIN2 USB VBUS is 300mA, and the current consumption of VIN1 5V drops to 700mA.
    The total current consumption of VIN1+VIN2 is 1A, which is the same as 1. It appears that both VIN1 and VIN2 are output to VOUT.
I suspect that the internal FFT of the TPS2116 may be short.
What could be the cause of TPS2116 causing these symptoms?
The 5V input of VIN1 and VIN2 are both tyv 5.0V, and the voltage exceeding the absolute maximum rating of 6V is not applied.

Best Regards,

Hiroyuki Taguchi

  • 0
    Expert 1245 points

    Hi,

    I would like to ask an additional question.

    Q1. 

    In the case of VIN1=floating, VIN2=USB VBUS 5V input, 5V is output to VOUT, but is it correct to understand that it is operating in the mode shown in the red frame in the figure below?

    Q2.

    Which input, VIN1 or VIN2, is used for the power supply of "Control logic and gate drivers" in the datasheet Function Block Diagram?

    Best Regards,

    Hiroyuki

  • 0 in reply to user244678
    TI__Mastermind 19340 points

    Hi Hiroyuki-san,

    It looks like your part has been damaged. I see only 1uF capacitance on the inputs - I've seen before where when the part switches over, cable inductance and switched power supply delay cause the input voltage to temporarily go over 6V and that breaks the part. Can you swap the part with a new one and confirm the behavior, and if that's the case, put a bigger input capacitance on the device?

    Q1. Yes, that's correct.

    Q2. Whichever input is higher powers the device circuitry - there's a description of this in the Iq section of the data sheet Electrical Characteristics table.

    Thanks,

    Patrick

  • 0 in reply to Patrick Shalton
    Expert 1245 points

    Hi Patrick,

    Thank you for your reply.

    I will replace the device with a normal one and check if it temporarily exceeds 6V.

    I understand the answers to Q1 and Q2. thank you.

    Thanks,

    Hiroyuki

  • 0 in reply to user244678
    TI__Mastermind 19340 points

    Hi Hiroyuki-san,

    Thank you, please let me know the results and if you have additional questions.

    Thanks,

    Patrick