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Original question:

TPS54320: condition of I/O short

TPS54320: condition of I/O short

user5006534
Prodigy 90 points
Part Number: TPS54320

Hi Team.

When Vout line is short circuited to another power line,
TPS54320 broke.
Vin and PH terminals are short circuited.

Vin = 5V
Vout = 3V
another power = 4.7V

I want to know the reason of I/O short.
This does not applicable tha case that short VOUT to a voltage greater than VIN.

  • 0
    Prodigy 90 points

    I have additional information.

    circuite is shown.

    My thoughts are below.

    When Vout line is short circuited to another power line,
    TPS25942 stop output detecting overcurrent.

    Therefore, VOUT short to a voltage greater than VIN.
    TPS54320 broke.

    I have a question
    Is it possible that reverse biased diode is connected to Vout and Vin？6746.circuite.pdf

  • 0 in reply to user5006534
    TI__Prodigy 30 points

    Hello,

    Here are my thoughts on the schematic and your observation of Vin shorting to PH when a 4.7V supply is connected to the Vout node:

    Schematic:

    • The inductor size of 22uH is fairly large and results in very little inductor ripple current.
    • The feedback resistors are correctly sized for 3V Vout. When the 4.7V rail is connected to Vout, then the voltage on the Vsense pin is 1.23V rather than the 0.8V that is used for proper function of the converter.
    • Cout is sized appropriately

    Observed Shorting of Vin to PH:

    • Having Vout greater than VIN will cause the body diode on the internal FET to conduct without any current limit. This definitely is not desired and may cause damage to the device.
    • There is a large error being introduced to the control logic when 4.7V is connected to the output. As mentioned above, there will be 1.23V at the Vsense pin which will create a large error signal.
    • With the small Voltage drop (300mV) across the inductor during the application of 4.7V to the Vout node (and 5V on the PH node during the ON time), the rise of the current in the inductor is slower than when 3V is at Vout.
    • These conditions result in the peak current mode control of the converter turning ON the high side FET for 100% of the switching cycle.
    • This 100% duty cycle results in the observed shorting of the Vin and PH pins.

    Please let me know if you have any questions.

    Thanks,

    Kyle Patrick