DC input and battery charging

peach-pi uses a TI TPS65090 combination PMIC and battery charger. The two power sources for peach-pi are the 12V DC input from the AC wall adapter and the battery, both of which feed into the TPS65090.

The TPS65090 has DCDC[1-3] voltage rails which feed a number of system components. One of these rails feeds a MAXIM MAX77802 PMIC.

TODO: determine which DCDCn rail from TPS65090 feeds into MAX77802.

DCDC1 feeds cortex-A15 cluster but not only. When chromebook2 is running on battery, the power consumption of DCDC1 is null when cortex-A15 cluster is in power down.


No public data sheet exists for this part, but Google searching reveals it to be a common PMIC on many devices (just look at how often it is used in mainline Device Trees!).

Based on the peach-pi DTS files it is clear that the MAX77802 feeds the Cortex-A7 and Cortex-A15 cpu clusters inside the Exynos5800 AP. Using this knowledge we can search for the MAX77802 part on the mainboard and probe resistors that surround it, allowing us to map out the physical voltage rails and probe them for power consumption.

After disassembling your peach-pi and removing the heat pipe, you can find the MAX77802. It is near the AP and surrounded by many small SMD resistors.

TODO: upload photo showing MAX77802 and establishing the orientation that the AP is "up", ribbon is "down".

Current state of voltage rail identification

So far all of the voltage rails on the left side of the MAX77802 scale voltage together, in a "measured" range from 880mV to 1.4V.

TODO: upload picture from lab notebook showing findings

TODO: upload computer graphic illustrating resistors with their voltage range and names

WorkingGroups/PowerManagement/Doc/peach-pi_power (last modified 2015-02-04 13:23:27)