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TPS62873: Ramping up the output voltage doesn't follow the datasheet.

Shunsuke Yamamoto
Expert 7261 points
Part Number: TPS62873

Tool/software:

Hi team,

My customer has been evaluating start up voltage function based on the EVM(TPS62873EVM-144). My customer writes VSET[7:0](0.6V) and VRANGE[3:2](1.25mV steps) to TPS62873 via I2C interface after Input power supply of 3.3V gets stabled. And then TPS62873 is enabled.

Based on the datasheet, After EN is high, the output voltage first ramps up to the target voltage set by VSEL pin, and then new programmed value are set. In my understanding correct?

But actual evaluation on the customer's side, after EN is high the output voltage first ramps up to the target voltage set by VSEL pin. That's all. By making EN low and high again, the output voltage ramps down to new programmed value.

Could you please kindly let me know which one the correct operation is?

Best regards,

Shunsuke Yamamoto

  • 0
    TI__Intellectual 960 points

    Hi Yamamoto san,

    Thanks for using e2e.

    Yes your understanding is correct. The output voltage should first go to the target voltage set before EN goes high and then change to the new programmed value.

    In your customer's case, output voltage first went up to 0.6V, and then didn't change to the new programmed value. Do I understand it correctly?

    If yes, can you please provide more information of the new programmed output voltage? I will try to check the behavior on an EVM.

    Thank you and best regards,

    Jingyi

  • 0 in reply to Jingyi Liu
    TI__Expert 7261 points

    Hi Jingyi-san,

    Thank you for the reply. The output voltage is first 1.2V, and 0.6V secondly. The startup sequence is below.

    Input voltage on and EN low -> Programming 0.6V and 1.25mV steps -> EN high -> Output voltage becomes 1.2V -> Programming 0.6V and 1.25mV steps -> 0.6V.

    Best regards,

    Shunsuke Yamamoto

  • 0 in reply to Shunsuke Yamamoto
    TI__Intellectual 960 points

    Hi Yamamoto san,

    Thanks for the information :). I will try to do the bench measurement as soon as possible.

    Best regards,

    Jingyi

  • 0 in reply to Shunsuke Yamamoto
    TI__Intellectual 960 points

    Hi Yamamoto-san,

    I want to check with you again before go to the lab.

    Is your customer using 2 devices in stack? Besides, on EVM TPS62873EVM-144 the default device is TPS62873-Q1 (automotive version). Have your customer changed the devices to TPS62873 (industrial version)? 

    Thank you and best regards,

    Jingyi

  • +1 in reply to Shunsuke Yamamoto
    TI__Intellectual 960 points

    Hi Yamamoto-san,

    I did the bench measurements with the GUI, and found the GUI can be misleading indeed. I'm sorry about this issue and our team will try to solve it.

    I assume your customer use the GUI like this to choose the step and Vset: 

    Here the Vset is not updated directly after changing the voltage steps. One way to solve it is to drag the Vset bar a little bit to actually 'update' the output voltage.

    But I would recommend to directly choose the step and Vset from the register page, as shown below. Here we can write data into the register for sure.

    Or, if possible, customer can also choose the 10mV steps, which can support output voltage from 0.8V to 3.3V.

    Thank you and best regards,

    Jingyi

  • 0 in reply to Jingyi Liu
    TI__Expert 7261 points

    Hi Jingyi-san,

    My customer has confirmed that the datasheet is correct based on their original board. Thank you for your quick support.

    Best regards,

    Shunsuke Yamamoto

  • 0 in reply to Shunsuke Yamamoto
    TI__Intellectual 960 points

    Hi Yamamoto-san,

    Good to hear that :). Thank you for the update.

    Best regards,

    Jingyi