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TPS65912: Question about TPS659127 Sleep Mode

Part Number: TPS65912

Hello,

During enter sleep mode of TPS659127,  some devices work abnormally.

With Vin = 3.8V, most devices' current consumption is around 4mA at sleep mode.

But some devices'  current consumption is around 12mA. 

Customer find that DC-DC4(3.3V) is operating in PWM mode continuously at that time.

In normal sleep mode, switched to PFM mode. 

With  Vin >= 4V, switched to PFM mode and normal current cunsumption around 4mA.

Customer wants to know why some devices cannot switch to PFM mode automatically with Vin = 3.8V?

And why sleep mode works normally with Vin >= 4V?

Please check and let me get your answer ASAP.

Regards,

Nicky

  • Nicky,

    Thank you for reaching out through E2E. I will look into this and get back to you shortly. If you are able to provide a schematic or information as to what external components you have on the output rails, that would help.


    Thanks,
    Nastasha
  • Nicky,

    After looking into this in the lab, it is determined that this is the expected behavior of this device. I do not have the information as to why it was designed in this way. Please let us know if you need further assistance for your application.

    Thanks,
    Nastasha
  • Hi Nastasha,

    I have one question about your answer. "it is determined that this is the expected behavior of this device".

    Customer tested 40 devices, but only 18 devices work as I described. If it is determined, why all device do not work the same?

    And there is my miss understanding about customer's sleep mode states.

    Customer's device is in sleep mode but PMIC is not in sleep mode. So, its output also alive.

    I attached DCDC4 parts schematic. Please refer attached.

    Customer wants to know 

    1. What conditions make PWM mode / PFM mode switching?

    2. Why over 4V input voltage it operates PFM mode and under 4V input voltage it operates PWM mode?

    Please check and let me know.

    Regards,

    Nicky

  • Nicky,

    Unfortunately, we do not have the information as to why this device is designed to switch into PFM at a certain threshold. Is this affecting your design? If so, please let us know how we can help.

    Thanks,
    Nastasha