Moreover, there are power rail dependencies, meaning that not everything comes on at once:
Code:
8.3.2 Dependencies Between Rails
Charge pumps, LDOs, and VCOM driver are dependent on the positive and inverting buck-boost converters and
several dependencies exist that affect the power-up sequencing. These dependencies are listed below.
• Inverting buck-boost (DCDC2) must be in regulation before positive boost (DCDC1) can be enabled.
Internally, DCDC1 enable is gated by DCDC2 power good.
• Positive boost (DCDC1) must be in regulation before LDO2 (VNEG) can be enabled. Internally LDO2 enable
is gated DCDC1 power-good.
• Positive boost (DCDC1) must be in regulation before VCOM can be enabled. Internally VCOM enable is
gated by DCDC1 power good.
• Positive boost (DCDC1) must be in regulation before negative charge pump (CP2) can be enabled. Internally
CP2 enable is gated by DCDC1 power good.
• Positive boost (DCDC1) must be in regulation before positive charge pump (CP1) can be enabled. Internally
CP1 enable is gated by DCDC1 power good.
• LDO2 must be in regulation before LDO1 can be enabled. Internally LDO1 enable is gated by LDO2 power
good.
So, as well as battery voltage and the input voltage to the chip, we will have to look at the pins associated with DCDC2 as well as the pins for DCDC1.
The top half of the typical application gives a hint as to some useful measuring points and pins of interest.