TPS6594-Q1: VCCA and POWERON Enable available, but sometimes not power output on PMIC's outputs

Hello Max,

Here's the User's Guide for the dual pmic solution for the DRA821U: Powering DRA821 with TPS6594-Q1 and LP8764-Q1 (Rev. A)

Max Chen1 said:

Q1: what possible causes make both PMICs no output?

A power error that doesn't get removed would cause the PMIC to not have an output. If an error occurs, the PMIC will typically reboot and if the error is not fixed/removed, the PMIC will reset until the threshold is reached, 15 attempts. Please read the interrupts of 0x5A - 0x6C on both PMICs if any errors are caused it will show that, you can read the datasheet's portions on registers.

Max Chen1 said:

Q2: I have SOC_PWR_EN for PMIC A: PWRON_L/ENABLE, what enable for PMIC B? PMIC B enabled by VINT_LEOA_1V8 from PMIC A?

PMIC A send a command over the SPMI bus, this communication bus is very specific to the PMICs, see the datasheet for more details.

Please have a printout of the interrupts after the failure, read them from I2C if you can (on both PMICs). 

Max Chen1 said:

I have VCCA and Power enable signal high for PMIC A, but it still no any power rail output sometimes, what is the cause?

An error occurred, please look at the interrupts, if that's not possible, please get an oscilloscope and test through the power up sequence on the board, see where in the power sequence the rails fail to continue to power up.

BR,

Nicholas McNamara