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TPS65261-1: Technical Inquiry Regarding PGOOD Function Implementation in TPS65261-1

SHENG YANG
Expert 1320 points
Part Number: TPS65261-1

Tool/software:

Hi team,

We are currently planning to use two TPS65261-1 devices to build a power supply system for motherboard power delivery, and have technical questions regarding the implementation of the PGOOD function that we hope TI engineers can clarify. Thank you for your support.

①As shown in the datasheet excerpt below: "When all buck channels are within regulation range and the power sequence is completed, the PGOOD signal will be asserted high". If I'm not using all three channels but only one or two channels, will the PGOOD signal remain permanently low?

②Does the [PGOOD Deglitch Time] shown in the figure below refer to the 512 cycles parameter listed in the specifications table?

  • 0
    TI__Genius 10470 points

    Hi,

    SHENG YANG said:
    ①As shown in the datasheet excerpt below: "When all buck channels are within regulation range and the power sequence is completed, the PGOOD signal will be asserted high". If I'm not using all three channels but only one or two channels, will the PGOOD signal remain permanently low?

    All 3 EN pins should be enabled for PGOOD to assert high irrespective of using 1/2/3 channels. 

    SHENG YANG said:
    ②Does the [PGOOD Deglitch Time] shown in the figure below refer to the 512 cycles parameter listed in the specifications table

    Yes, you're right. 

    Regards,

    Gautam

  • 0 in reply to Gautam Iyer
    Expert 1320 points

    HI

    Thanks for your response.

    As shown in the figure below, two TPS65261-1 devices are used with a total input voltage of 12V.Power supply ① (TPS65261-1) generates 5V, while power supply ② (TPS65261-1) produces 1.1V and 1.5V. The 1.5V output then enables power supply ① to generate 3.3V and 2.5V.

    Subsequently, the PGOOD signal from power supply ① enables the third channel (1.8V power output) of power supply ②.
    Can this sequence of operations be implemented as described? Thank you.

    Both power ICs have their MODE pins grounded.



  • 0 in reply to SHENG YANG
    TI__Genius 10470 points

    Thanks for the brief description on power sequencing. As I mentioned earlier, as soon as EN1,2 & 3 cross Venxh threshold - PGOOD would assert high. 

    Regards,

    Gautam

  • 0 in reply to Gautam Iyer
    Expert 1320 points

    HI Gautam Iyer

    Thanks for your response.

    Sorry, I didn't understand. If only BUCK1 is used (with no power inductors for BUCK2/BUCK3 outputs), will PGOOD assert high as long as EN1/EN2/EN3 exceed the Venxh threshold and BUCK1 output voltage is stable?  Is it not necessary to consider all three FB signals?


  • 0 in reply to SHENG YANG
    TI__Genius 10470 points

    When I mentioned enable EN1/EN2/EN3; I assumed all 3 bucks are populated and generating right output. 

  • 0 in reply to Gautam Iyer
    Expert 1320 points

    HI Gautam Iyer

    Thanks for your response.

    Could the TPS65261-1 be used with only one output channel operational? For instance, utilizing BUCK1 while leaving BUCK2 and BUCK3 inactive. In this scenario, what would be the status of PGOOD?

  • 0 in reply to SHENG YANG
    TI__Genius 10470 points
    SHENG YANG said:
    For instance, utilizing BUCK1 while leaving BUCK2 and BUCK3 inactive. In this scenario, what would be the status of PGOOD?

    PGOOD will be asserted low in this case. Again, inactive meaning no output voltage with EN2/3 disabled. 

  • 0 in reply to Gautam Iyer
    Expert 1320 points

    HI Gautam Iyer

    Thanks for your response.

    ①If only BUCK1 is used while BUCK2 and BUCK3 are unused (with no output power inductors and feedback circuits), and if PGOOD functionality is desired, then EN2 and EN3 need to be pulled high. In this configuration, when BUCK1's output voltage is normal, PGOOD can also be pulled high. Is this understanding correct?

    ②If only BUCK1 is active while BUCK2 and BUCK3 are disabled (with no output power inductors or feedback circuits present), and if EN2 and EN3 are pulled low, then PGOOD will remain low even when BUCK1's output voltage is normal. Is this interpretation correct?

  • +1 in reply to SHENG YANG
    TI__Genius 10470 points
    SHENG YANG said:
    ①If only BUCK1 is used while BUCK2 and BUCK3 are unused (with no output power inductors and feedback circuits), and if PGOOD functionality is desired, then EN2 and EN3 need to be pulled high. In this configuration, when BUCK1's output voltage is normal, PGOOD can also be pulled high. Is this understanding correct?

    Yes, EN2 and EN3 have to be pulled high plus both FB pins should be fed with the output. 

    SHENG YANG said:
    ②If only BUCK1 is active while BUCK2 and BUCK3 are disabled (with no output power inductors or feedback circuits present), and if EN2 and EN3 are pulled low, then PGOOD will remain low even when BUCK1's output voltage is normal. Is this interpretation correct?

    Correct. 

    Regards,

    Gautam