Power management is one of the more complex parts of the project. Power regulators are expected to dominate the amount of ICs (integrated circuits; chips) used in the design.
Overview
As a tablet computer, MediaCow Touch 2 contains a rechargeable battery pack.
MediaCow Touch 2 would charge off from USB Type-C Power Delivery that is supported by both USB Type-C ports present.
LattePanda Mu
The LattePanda supports a wide voltage input of 9v to 20v, this allows the module to be powered directly off from system power that could be anywhere between 12v (worst case) and 20v.
Battery
With difficulties finding battery packs for DIY usage that have the ability to report state-of-charge; have a fuel gauge. I used a battery pack intended as a replacement battery pack for an existing laptop, specifically the HP FM08 used in the HP OMEN 17-an008ca among others. The pinout and connector type is unknown at the moment.
In January 2025, I had the idea of making my own battery pack, using four of Adafruit's 10050mAh 3.7v battery packs in a 4S3P configuration using a custom BMS board, resulting in a 14.8v 10Ah (148.74Wh) battery pack. This is about 3.72 times the battery capacity of the Steam Deck at 40Wh and 1.7 times the capacity of the HP FM08 battery pack at 86Wh.
Voltage Supplies
System Power - VSYS
System Power is the main supply that is directly from the battery or USB Type-C ports. Worst case voltage for the battery is 12v. Power from USB Type-C is expected to be 20v.
This supply is always available while the system is powered on or off.
LattePanda Mu input voltage - VSYS_SW
VSYS_SW is a switched power supply that powers the LattePanda Mu. An Infineon BTS7003-1EPP is used to switch the voltage. Due to the relatively high voltage of VSYS, only automotive-grade parts such as the BTS7003-1EPP were available.
The BTS7003-1EPP has a unique sense pin feature that allows a microcontroller to read the voltage and current, a bit of research was done to see how this could be implemented with the SP7021, even going to a junkyard to see if I could find this component in a vehicle. Due to the part being recent, with the datasheet dating 2018, I have not been able to find this part in a vehicle. I used this as more of an excuse to go to the junkyard.
As recommended in the datasheet for the BTS7003-1Epp, a zener diode on the sense output is used to protect the microcontroller from possible overvoltage.
SMEC input voltage - SMEC_5V
SMEC_5V is a pre-regulated 5v supply that feeds directly to the PMIC for the SP7021.