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TPS65219: TPS6521901 issue

yuan qu
Prodigy 50 points
Part Number: TPS65219


Hi teams,

from TPS65219 recommend circuit the PVIN_LDO2 is from 1.8V discrete buck output. but i don't use separate DCDC as DVDD1.8V，so if i could use 3.3V output from Buck 1 to use as PVIN_LDO2?

and the output of LDO2 could also has the sequence of 5th? Thank you

  • 0
    TI__Mastermind 23301 points

    Hello,

    Thank You for using E2E! When using the TPS6521901, LDO2 input supply can come from the external 1.8V discrete or from Buck2 (3.3V). We recommend using the external 1.8V discrete because it provides a lower power dissipation. 

    If a discrete LDO is not used, how will the 1.8V IO domain (DVDD1V8) be supplied? 

    Thanks,

    Brenda

  • 0 in reply to Brenda Diaz
    Prodigy 50 points

    hi, Thank you. due to my design don't have SD card, so i connect LDO1(fixed 1.8V) to DVDD1V8(our system 1.8V IO don't need big current.)  

    that's why i don't use discrete DCDC. is that okay for my design?

  • 0 in reply to Brenda Diaz
    Prodigy 50 points

    or if i could connect Buck3(1.2V) to VIN_LDO2? because Buck3 has the 3rd power sequence and LDO2 output should be 5th power sequence.

    and this also could lower the dissipation. is this scenario  be better?

  • 0 in reply to yuan qu
    TI__Mastermind 23301 points

    Hi,

    Yes, if the application doesn't have SD card, LDO1 could be used to supply the 1.8V IO domain and the VSEL_SD pin will need to be connected to GND. Please make sure VSEL_SD pin is not controlled by the processor to make sure the output voltage on LDO1 doesn't change.

    Regarding the input voltage for LDO2, the 1.2V (from Buck3) cannot be used because the minimum input voltage for LDO2 specifically is 1.5V. 

    Thanks,

    Brenda

  • 0 in reply to Brenda Diaz
    Prodigy 50 points

    okay, yeah. thank you for correcting.

    so i think i will connect DVDD3.3V to VIN_LDO2. and this VDDR_CORE current is very small(i checked MCU benchmark test report, it's about 10mA+ ). so i think the power dissipation is not a big issue.

    any suggestions here?

    because i don't want to add extended DCDC/LDO...that way....

  • +1 in reply to yuan qu
    TI__Mastermind 23301 points

    Hi,

    Yes, LDO2 can be supplied from the same 3.3V rail (Buck2) that is supplying the other LDOs of the PMIC. 

    Thanks,

    Brenda