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TPS650864: Power sequence

Guru 16770 points
Part Number: TPS650864
Other Parts Discussed in Thread: CSD87350Q5D, , TPS650861

Hi

We are considering TPS6508640 to be used along with Xilinx ZU7EV.

Ordinally, 0.85V rail, such as VCCINIT etc, requiring large current consumption.

(Our estimation is over 30A or so)

So, we will use BUCK2 controller with CSD87350Q5D for this rails.

I have questions for power sequences.

1. TPS6508640 will operate with the default value listed in Table 3-1 of the datasheet.
Is it possible to change these default values?

2. If the answer to question 1 is “NO”,
is it possible to change the output voltage after starting up with default value?

3. Figure 6-4 and Figure 6-5 of the datasheet show power up/off sequences.
Are these sequences just fixed? Or changeable by user?

BestRegards

  • na na78 said:
    1. TPS6508640 will operate with the default value listed in Table 3-1 of the datasheet.
    Is it possible to change these default values?

    No, it is not possible to overwrite the OTP (one-time programmable memory) settings. They are not re-writable EEPROM memory.

    na na78 said:
    2. If the answer to question 1 is “NO”,
    is it possible to change the output voltage after starting up with default value?

      Yes, it is possible to change by writing I2C commands to the VID registers for each BUCKx and LDOx regulator.

    na na78 said:
    3. Figure 6-4 and Figure 6-5 of the datasheet show power up/off sequences.
    Are these sequences just fixed? Or changeable by user?

    The sequences are fixed, and they will begin executing when the first CTLx pin is set high. Using TPS6508640 as an example, CTL3 = high begins the power-up sequence ("and CTL1 if used"). If you want to modify the power-up sequence by I2C, you would need an MCU that is powered by LDO_3P3 or an external LDO that can write I2C commands to the TPS650864 PMIC to modify the voltage and enable them at the correct time. If I2C is used to control the PMIC, setting the CTLx pins high can still be used but is not required.

  • Hello,

    CSD87350Q5D is an excellent choice for high current.

    The TPS650864 family is a pre-programmed variant of the TPS650861. The TPS650864 devices cannot be re-programmed, but you can program a TPS650861 to be  the same as  TPS6508640 but with a few specific changes. We provide a pre-filled OTP Generator to allow for minor changes to be a relatively easy step. These are on the "Design tools & simulation" tab of the design and development on the TPS650861 product folder:

    That said, you can change the voltages after boot using I2C. The will reset whenever power is lost or the device does a reset (OTP reload).

    You cannot change the sequencing by I2C, only by programming a TPS650861.

  • Hi Brian 

    Thank you for your reply.

    I understood the output value is changeable by writing I2C.

    In this case, I think TPS650864 will work with default value at first.

    Is it possible to disable default output before starting power sequence?
    I want to confirm I could make TPS650864 work with required VID value from the first.

    BestRegards

  • Hi Kevin

    Thank you for your reply.

    I also considered TPS650861 which is user programmable OTP memory version.
    But I hesitated to use TPS650861 because some tasks to program it would be required, and I felt difficulty.

    However, TPS650861 is very flexible anyway so I will try to check TPS650861 also.

    BestRegards

  • na na78 said:
    Is it possible to disable default output before starting power sequence?

    Yes, you need to make sure CTL3 and CTL1 pins are low. Then you can write to I2C and modify any value in the Register Map.