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TPS63031: Excessive current consumption

Evgeni Kosakovski2
Prodigy 30 points
Part Number: TPS63031

Hello.

We have a similar problem as in this post: https://e2e.ti.com/support/power-management/f/196/t/48432?TPS63031-Possible-excessive-current-consumption . We are developing a project with a microcontroller and a touch toggle switch powered by a Li-ion battery. For 3.3V voltage stabilization we use DC/DC TPS63031. The system is always off. When the user presses the touch sensor, the switch turns on and the voltage starts the microcontroller and peripherals. In the working state, the system consumes a current of 90mA, and in the off state, the consumption should not exceed 600uA (periphery from charger to toggle switch). But, as I see it, in the off state, DC/DC consumes 3mA: we gradually disconnect all the peripherals that follow the DC/DC until the charger and DC/DC remain. The charger itself does not consume current (we removed the DC/DC and left only the charger).
We took the Typical application from the datasheet as the basis for the connection. But now I understand that it is necessary to make changes. In this regard, I would like to understand how to do it correctly:
1. Do you need to connect PS/SYNC to ground to enable power save mode?
2. DC/DC is always connected to the touch sensor, which consumes 59uA. Does EN need to be connected to VIN in order to put the DC/DC to operation, or can it remain connected as it is now, across a capacitor to ground?
3. Do I need to change the VINA connection?
4. What is the minimum DC/DC current consumption I should have with the switch off, 35uA, or is it some other state other than Quiescent current (Shutdown 0.9uA)?
5. Is it possible to input DC / DC into Shutdown current when I connect, so that the touch switch continues to work and can turn on all peripherals?
Connection diagram is attached.
  • 0
    TI__Expert 4760 points

    Hi Evgeni,

    The main cause of large current consumption is that the device works in FPWM, so you need to connect PS/SYNC to ground to enable power save mode.

    The VINA and EN pin connection should not be changed. 

    The minimum DC/DC current consumption you should have with the switch off is above 35uA. 35uA is maximum Iq which is measured when EN is high without switching. You can read the article below to understand better. No load current, which is what you desired, is measured when EN is high and with switching. It should be hundreds of uA if power save mode is enabled.

    Best Regards,

    Yichen

  • 0 in reply to Yichen Xu
    Prodigy 30 points

    Hi Yichen.

    Thanks for your reply and the document. But I have additional questions:

    1. What will change if connect EN to the VIN?
    2. VINA is Supply voltage for control stage. What does this mean? What is its functionality? What will change if connect VINA to the VIN or to the GND?

    How does this affect current consumption?

    Evgeni

  • 0 in reply to Evgeni Kosakovski2
    TI__Expert 4760 points

    Hi Evgeni,

    VINA means the internal power source for the device, it supply the power consumption of device. From the picture below you can see VINA is derived from VIN, they are connected with a resistor. And there is a 0.1uF capacitor outside. So VINA is derived from VIN with a RC filter, to avoid noise of input side. So connecting EN to the VIN will not affect to much, but EN voltage will not be filtered and might be interrupted. And since VINA is already connected to VIN inside, it can never be connected to GND because it will cause shorting. 

    This will not affect no load current. Allowing power save mode will reduce power consumption at light load and reduce current consumption.

    Best Regards,

    Yichen Xu

  • 0 in reply to Yichen Xu
    Prodigy 30 points

    Hi Yichen.

    We will correct our design and then check it on a new PCB. Thank you for your help.

    Evgeni