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Original question:

TPS65313-Q1: Conditions for operation without MCU

TPS65313-Q1: TPS65313-Q1: No Output on Buck1/Buck2/Boost – Custom Board Not Switching

Lee DongJae
Prodigy 20 points
Part Number: TPS65313-Q1

Tool/software:

Dear TI Support Team,

I would like to ask a follow-up question regarding the TPS65313-Q1, which I am planning to use as a PMIC in my design.

Previously, I suspected that the issue was caused by providing only 5V to the WAKE pin, but I have since revised the circuit to ensure the WAKE pin receives approximately 11.5V (as measured with an oscilloscope). Despite this, I still do not observe any output from Buck1, Buck2, or the Boost converter — i.e., no 3.3V, 1.2V, or 5V outputs.

I designed my custom board based on the schematic provided in the EVM kit datasheet. However, I am unsure why the regulators are not turning on.

From what I can tell, there seems to be no switching activity at the Boot1 output, and I cannot identify the reason for this behavior.

Since I do not plan to use any external power source, I connected Ext_Vsen1, Ext_Vsen2, and Extsup to GND — just as shown in the EVM when those functions are unused. However, this setup still does not result in any output voltages, and I am also not observing any waveform on the VREG pin.

I would greatly appreciate your support in identifying what could be going wrong.
I will attach my schematic for your reference.

Please note that this setup is intended only for testing the power outputs, so the MCU is not connected to the board.
SPI communication is also not connected.
Pins 7 to 11, as well as all SPI-related pins, are left unconnected.

As mentioned earlier, I designed the schematic by closely referencing the TPS65313-Q1 EVM kit.
It should be nearly identical to the EVM.
If there is anything incorrect or missing in my implementation, I would greatly appreciate your advice or suggestions.

Thank you very much for your help.

Sincerely,
Lee

  • 0
    Prodigy 20 points

    Additionally, I am supplying 12 V to the AVIN pin, but the VREG output remains at 0 V — even under conditions where the internal LDO should be active.
    I also tried supplying 5 V to the EXTSUP pin, but the VREG output still does not appear.

    This seems to be the core issue preventing the device from powering up properly.

  • 0 in reply to Lee DongJae
    TI__Genius 17060 points

    Hi Lee,

    What OPN is used here?

    I need to check and get back to you on this. 

    Regards,

    Ishtiaque 

  • 0 in reply to Ishtiaque Panhwar
    Prodigy 20 points

    Hi Ishtiaque,


    The OPN used here is O31310QRWGRQ1.

    Regards,
    Lee

  • 0 in reply to Lee DongJae
    TI__Genius 17060 points

    Hi Lee,

    Thanks for the update. I will get back to you soon. 

    Regards,

    Ishtiaque

  • 0 in reply to Ishtiaque Panhwar
    Prodigy 20 points

    Hi, Ishtiaque,

    thank you for the quick reply

    I'm wating for your reply

    Regards,
    Lee

  • 0 in reply to Lee DongJae
    TI__Genius 17060 points

    Hi Lee,

    While reviewing the schematic, in EVM schematic, the diodes on the switch are not populated.  can you check that and try to un-populate those. 

    Regards,

    Ishtiaque 

  • 0 in reply to Ishtiaque Panhwar
    Prodigy 20 points

    Thank you for response.

    I have confirmed that the diodes are not mounted on the board I manufactured, as indicated by DNP on the EVM. The diodes are unpopulated, yet under these conditions, no voltage is output.

    Regards,
    Lee

  • 0 in reply to Lee DongJae
    TI__Genius 17060 points

    Hi Lee,

    Thanks for the confirmation.  I need to look at this and get back to you by Friday tomorrow. 

    Regards,

    Ishtiaque 

  • 0 in reply to Ishtiaque Panhwar
    Prodigy 20 points

    Thanks you for help. ! I'll be wating

    Regards,

    Lee

  • 0 in reply to Lee DongJae
    TI__Genius 17060 points

    Hi Lee,

    Sorry for the delay. I haven't be able to figure out what could be the cause or missing here which is preventing you from power up. 

    1. Have you tried to swap with another sample ?
      1. And see if that has the similar issue.
    2. Have you checked if it could be soldering issue, for some reason if the device is not properly soldered on the board. 
    3. Another have you checked populating the same device on the PMIC EVM, if you happened to have the EVM for example.
      1. Does that work?

    Regards,

    Ishtiaque

  • 0 in reply to Ishtiaque Panhwar
    Prodigy 20 points

    Hi, Ishtiaque

    I have fabricated a total of four guide boards, and since all four boards have identical circuits, none of them output any voltage.

    It appears that the same issue is occurring on all boards.

    We have not checked for soldering issues yet. (We will check further to be sure.)

    Do you mean that we should remove the PMIC from our fabricated board and replace it with the PMIC from the EVM? We will try this.

    I have not tried mounting the TPS65313-Q1 from our fabricated board onto the EVM TPS65313-Q1.

    I will proceed with these additional steps and get back to you with an update.

    Regards,
    Lee

  • 0 in reply to Lee DongJae
    TI__Genius 17060 points

    Hi Lee,

    Upon reviewing the schematic and comparing to EVM, I find following discrepancies. 

    1. Ext_Vsense1 and Ext_Vsense1  are Grounded in your schematic whereas in the EVM schematic these are supplied 0.8V from VIO via voltage resistor divider.  

    2. EXT_SUP in your schematic seems to be connected to GND. This should be connected to Ext_sup  5V but I think as far as I can read your schematic the R27 seems to be NC. IF that is the case then I think as per EVM schematic this should be populated and R28 should be NC. 

    Regards,

    Ishtiaque

  • 0 in reply to Ishtiaque Panhwar
    Prodigy 20 points

    Thank you, Ishtiaque,

    According to the datasheet, for the Ext_Vsense1, Ext_Vsense2, and Ext_Sup pins, if they are not used, they should be tied to GND. I have confirmed from the datasheet that if the Ext_Sup power is not used, the internal LDO is configured from the AVin voltage to generate Vreg. Since my intention is not to use Ext_Sup 5V, I believe connecting it to GND is correct.

    Regarding the EVM, it also operates internally even without supplying Ext_Sup 5V. Therefore, it seems that Ext_Sup is not currently relevant. Is it mandatory to use an external power for Ext_Sup?

    Additionally, for the prototype board, I have already applied 5V to Ext_Sup, but the symptom remained the same—no voltage output was observed.

    Regards,
    Lee

  • 0 in reply to Lee DongJae
    TI__Genius 17060 points

    Hi Lee,

    Since you are using the same OPN (O31310QRWGRQ1) as used on the EVM so you need to provide those external sense voltages  because it could be so that in the device NVM, those two external_vsense pins are configured to monitor the voltages and if you do not provide, the device may consider as fault and does not power. If you do not use in your application then you may need to modify those settings in the exiting NVM or ask for custom OPN which then can be reprogrammed as per your application use case. 

    To my understanding both above things are necessary. It doesn't hurt trying that since you are exactly copying the EVM design so you need to follow the EVM instructions for PMIC power up. 

    Regards,

    Ishtiaque