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TPS650942 BUCK1 (VNN) at S4/S5 satuts

LI FOX
Prodigy 10 points

Dear Sir,

TPS650942 BUCK1 (VNN) is high at G3 to S4/S5(cold boot). Why BUCK1 (VNN) is low at S0 to S4/S5(cold off)? What is the different?

Thanks!

  • 0
    TI__Genius 17380 points
    Hi Li,

    VNN is required to perform an A-to-S rail transition during operation according to the APL EDS (IBL#557555). The Cold Boot (Figure 4-1 in the EDS) shows VNN coming up first as an "A" rail.

    After the PMIC release PCH_PWROK, VNN becomes an "S" rail, meaning it is disabled when the processor enters sleep states. As a result, it becomes one of the first to power down per the Cold Off sequence (Figure 4-5 in the EDS).