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LP8758-B0: LP8758-B0 set to 0.9V

Kevin Huang67
Intellectual 370 points
Part Number: LP8758-B0

Hi Sir,

From your forum PMIC sense routing example in web, the far end voltage(1.18V) is lower than PMIC set=1.2V.

e2e.ti.com/.../how-to-implement-remote-sense-in-your-processor-power-design


Why the below case (Phil replied me on 6/30) is far end 0.968V higher than PMIC(LP8758-B0) set=0.9V ?

Your experience for PMIC(LP8758-B0) is working well when PMIC(LP8758-B0) set=0.9V, far end(11000 mil far away PMIC output) voltage=? V, I=?
[Yi, Phil] far end voltage=0.968V, if I=1A, PCB trace resistance=0.068 Ohm.

Can you help to explain the two cases' difference ?

  • 0
    TI__Genius 13216 points

    Hi Kevin,

    Thank you for posting on E2E. Phil is out of office today but will be back tomorrow to provide some insight.

    Thanks,

    Daniel W

  • 0 in reply to Daniel W
    TI__Mastermind 33140 points

    Hi Kevin,

      For remote sense connection, it's normal that far end voltage has higher level than local output when there is some load current passing through. If no load current passing through at all, both sides should have exact same voltage level. 

      For the case: the far end voltage is 1.18V which is lower than PMIC setting at 1.2V; it's normal if no load current passing through at all; since the PMIC could have <3% tolerance; this should be confirmed by checking its local output level; it should also be 1.18V. 

    Thanks!

    Phil

  • 0 in reply to Phil Yi40
    Intellectual 370 points

    Hi Phil,

    If the test chip current is from 0~1A, then suddenly the current drop from 1A to zero. The PMIC will keep at the 0.968V, so the far end is 0.968V. Is it correct? Why the PMIC not return to set=0.9V?

  • 0 in reply to Kevin Huang67
    TI__Mastermind 33140 points

    Hi Kevin,

      If there is no load current at all, then the far end should have same voltage level as the PMIC output. If PMIC output setup is 0.9V output, then the 0.968V output level is not correct since it's out of its <3% tolerance. Please check followings:

    1.  How many PMIC have the out of its <3% tolerance issue?
    2.  How many total PMIC units used in your project?
    3.  Can swap a new PMIC unit to solve the issue?

    Thanks!

    Phil