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TPS65094: spec check

GARETH OU
Guru 11615 points
Part Number: TPS65094


Hi

Customers want to test the Buck2 ( VCCGI) set of Power Rails in tps65094. This is APL GI Power Rail. It depends on SVID ( pin#58 CLK and pin#59 DATA ) to have Output voltage. Generally speaking, in the absence of CPU, PWM Control can set a voltage called VBoot, Come for Power RD to do the test. Can TPS65094 set this VBoot?

  • 0
    TI__Mastermind 32220 points

    Hi Gareth, 

    On TPS65094 Buck2 (VCCGI) output regulation voltage is default = 0V. Therefore I2C communication via host is required to set desired output voltage to test Buck2 rail. 

    GARETH OU said:
    Generally speaking, in the absence of CPU, PWM Control can set a voltage called VBoot, Come for Power RD to do the test. Can TPS65094 set this VBoot?

    I do not quite understand this part of your question, would you be able to rephrase for me? What exactly are you asking TPS65094 to do?

    Best Regards,

    Garrett 

  • 0 in reply to Garrett Kreger
    Guru 11615 points

    Hi Garrett

    TPS650947 SW1 +VNN Test Transient test.

    Blue is the current waveform.

    Yellow is the voltage waveform.

    When the current is light load, the voltage is different from the previous level. Any comments on this?

  • 0 in reply to GARETH OU
    TI__Mastermind 32220 points

    Hi Gareth, 

    Upon initial inspection I agree it is odd that the voltage behavior circled in red is different compared to the previous periods with light load current. Is this observation repeatable? Also is the customer using the recommended output capacitance (220 uF) listed on datasheet page 13? 

    Looking at the provided waveform even with the observed voltage difference the device maintains Vout according to the load transient regulation spec listed for BUCK1 on page 13 of the datasheet. I have included the spec below for reference. 

    Best Regards,

    Garrett 

  • 0 in reply to Garrett Kreger
    Guru 11615 points

    Hi Garrett

    1.Yes, Vout cap have 220uF/2.5V Pos-cap solution. But at light load, it is often seen that this type of waveform exists.

    2.TPS650947 buck 2 vccgi power rail, Loadline issue. Can this be adjusted?

  • 0 in reply to GARETH OU
    TI__Mastermind 32220 points

    Hi Gareth, 

    1)Thank you for confirming the customer has the correct output capacitor. Here are a couple things to note.

    First, the provided Vout waveform appears to have a bit of noise. If possible the customer should measure with a different probe to alleviate the noise and have a cleaner waveform.

    Second, when the load transitions from higher current to light load current the buck regulator switches from PWM mode to PFM mode. In PFM mode the device skips switch pulses to ensure higher efficiency, and will have slightly less voltage regulation accuracy. This may explain why every so often the regulation voltage at light load is slightly different. 

    Overall as stated above the difference in Vout is minimal and within the specification for BUCK1 listed on the datasheet. 

    2) Can you please clarify what you are looking to adjust with BUCK2? From what is shown on the included schematic the connections look to be correct.

    Best Regards,

    Garrett

  • 0 in reply to Garrett Kreger
    Guru 11615 points

    Hi Garrett

    2.Test Loadline >> When the normal load increases, the voltage will drop, and the efficiency will be better But customer test buck 2 vccgi Loadline load increase output voltage will not drop

  • 0 in reply to GARETH OU
    TI__Mastermind 32220 points

    Hi Gareth, 

    BUCK2 will attempt to regulate to the same voltage even when the load is increased. The figure included below is an application curve from the datasheet showing how BUCK2 voltage may initially drop slightly due to load increase, but it returns to the set regulation voltage. 

    Best Regards,

    Garrett 

  • 0 in reply to Garrett Kreger
    Guru 11615 points

    Hi Garrett

    The customer test load line voltage does not drop, so it cannot meet the intel specification
How to enable this function?
    Thanks
  • 0 in reply to GARETH OU
    TI__Expert 4985 points

    Hi Gareth,

    Due to the US holiday on September 5th, the response will be delayed. Expect a reply later this week.

    BR,

    Samuli

  • 0 in reply to Samuli Piispanen
    TI__Mastermind 32220 points

    Hi Gareth, 

    What is the intel specification (i.e. BUCK2 function) the customer is looking to meet? As mentioned above, by default BUCK2 output will regulate at the set voltage with a load current draw up to 21A. The results in the table provide agree with the expected operation of the TPS65094. 

    Best Regards,

    Garrett

  • 0 in reply to Garrett Kreger
    Guru 11615 points

    Hi Garrett

    But We can not measure test of Intel load line

    Intel VCCGI Load line spec is 6m ohm~

    Could you help us?

  • 0 in reply to GARETH OU
    TI__Mastermind 32220 points

    Hi Gareth, 

    Your question relates to this previous thread asking about Intel's DCLL spec, which I will link here: https://e2e.ti.com/support/power-management-group/power-management/f/power-management-forum/1035747/tps65094-apollo-lake-dcll-specification 

    As of now TI does not have information regarding how you would measure this Intel specification. All specifications relating to load and line regulation for VCCGI rail is listed on page 14 of TPS65094 datasheet. I will mention this device was used on the Intel Apollo Lake CRB, and therefore should meet the requirement. 

    Best Regards,

    Garrett