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TPS82130: TPS82130 output discharge

user6049718
Prodigy 95 points
Part Number: TPS82130
Other Parts Discussed in Thread: TPS62130A, TPS62135,

Does TPS82130 has output discharge function like TPS62130A or TPS62135 when the device is shut down by EN or UVLO?  I hope Vout is always lower than Vin  during power-down.

  • 0
    TI__Guru**** 150760 points

    Hi User,

    If you want, you can keep discussing this on your first thread.

    No, TPS82130 does not have output discharge.  However, the PG output can be used to sink some current just like the TPS62130A, since both devices hold PG low when EN is low.

    No device can force Vout to remain below Vin, for a sudden decrease of Vin to 0V for example.  Why is this needed in your application?

  • 0 in reply to Chris Glaser
    Prodigy 95 points

     TPS82130 Output Voltage Configuration with Digital Potentiometer(TPL0401A). 

     TPS82130 Vin and TPL0401A VDD use the same +5V power. 

    TPL0401A Power Sequence as below: 
    Protection diodes limit the voltage compliance at SDA, SCL, terminal H, and terminal W, making it important to
    power up VDD first before applying any voltage to SDA, SCL, terminal H, and terminal W. The diodes are forwardbiasing,
    meaning VDD can be powered unintentionally if VDD is not powered first.

    For protecting TPL0401A, I need to keep Vout to below Vin all the time in design. Could you help to check the design(during power on and power down)?  Or I need a DC-DC with output discharge function?Thanks a lot！

  • 0 in reply to user6049718
    TI__Guru**** 150760 points

    Thanks for sharing the circuit.  Are you concerned that a voltage will flow from Vout, through Rup and Rser, and into the TPL0401A?  Is this the current path?

    If TPS82130 uses 5V for its input, then Vout will not be present when the 5V is applied.  After 5V is applied, there will be some delay and then soft start before Vout is fully up.  The power up case looks ok for Vin > Vout.

    The resistors Rup and Rpar will discharge the output.  The time it takes can be calculated from an RC discharge circuit, where C is the total output capacitance.

    If you are concerned that the 5Vin can be removed and re-applied quickly, before a discharge is complete, you should probably control the EN pin of the TPS82130.  An MCU can do this or a simple RC delay circuit, as shown in #3 here: http://www.ti.com/lit/an/slyt730/slyt730.pdf

    You can check with the TPL engineers to see if there is any concern with power down.  If the Vdd supply voltage goes to 0V eventually, is there a concern?

  • 0 in reply to Chris Glaser
    Prodigy 95 points

    Hi, Chris

       Thanks for your reply.

         For discharging Vout, I will use a 330 resistor between PG and Vout. Using a 28K  resistor for Rup, the current will sink to PG MOSFET. 

         I will check with the TPL engineers to see if there is any concern with power down.

         Thank you very much.