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TLVM13640: Vout is provided externally (USB) before turning VIN on.

Lait Abu Saleh
Prodigy 70 points
Part Number: TLVM13640


Hi there,

I have an issue with the TLVM13640RDLR trying to generate a 5 V output from a 24 V input at VIN. The circuit has a USB-OTG port for standard communication and first programming of a processor module from within a pc. The design works fine in usual use-case. 

Whenever a connect the USB cable prior to connecting the power supply (24 V at VIN) the IC an unusual behaviour of the circuit happens. The 5 V rail is not stable anymore! 

Page 18 on the datasheet states: "The VLDOIN voltage must not exceed both VIN and 12 V."

Due to the connection of USB => VOUT1, VOUT2 and VLDOIN (shorted to VOUT1 and VOUT2 on the circuit) gets 5 V from USB (VBUS). VIN is still not active. This leads to VLDOIN > VIN (= 0V).

Does this harm the IC? Is there a work around to avoid this problem?

schematic of "TLVM13640" along with the used power switch (TPS2560DRCT) towards the USB connector. VBUS is acutally needed by the module for detection purposes...

 

Best

Lait

  • +1
    TI__Guru 50120 points

    Hello Lait,

    Note the spec in the datasheet. The VLDOIN should be no more than the lower of the two max spec (V_Vin+0.3 or 16V). 

    In the case where your VIN is off (0V), the VLDOIN should be no more than 0.3V. 

    If there is an external circuit that bias the "5V" rail, output of the TLVM13640 when the power module is off, this may be causing damage to the device.

    In such a case, it is recommended to have a reverse current blocking diode in series with the 5V output to prevent reverse current.

    Regards,

    Jimmy