Dual input lithium battery charger with 5V and 3.3V outputs
This board is a power management device with LiPO/Li-ion charger and a power supply with a DC-DC converter. The charger works with either DC wall adapter or USB.
The DC input operates from 4.15V to 16V with up to 20V protection.
The USB input has a range of 4.1V to 6.3V with up to 8V protection.
It is suitable for all Lithium cell batteries and has an end-of-charge voltage of 4.2V.
![resistors](https://www.openhardware.io//uploads/5844585be05bc30b20129722/image/Dual input charger_resistors_mala.png "enter image title here")
The 5V DC-DC boost converter provides a power supply output powered by either a battery or from DC and USB inputs. It can supply more than 1.2 A at 5V and provides high efficiency power conversion of more than 90%.
The 3.3V output is powered by a high efficiency XC6210 linear voltage regulator, which can supply more than 700mA.
When no DC or USB inputs are present, the output is powered by battery. It works as uninterruptible power supply (UPS). Both outputs have undervoltage protection and are turned off if the battery voltage drops below 3V. They both also have short-circuit protection.
There are two status LEDs. One is for input, the other indicates charging. The two charging resistors on the board set the currents. Rchg sets the battery charging current and Rin limits the overall DC input current (to reduce current draw if solar panel is used to charge the battery).
They can be replaced to change current values. This is the correlation:
Rin = 6000V/Iin-max
Rchg = 1200V/Ichg-max
The ones on the board are 4k7 (Iin limit is 1.227A, Ichg = 255mA)
5V output max current 2000mA
3.3V ouput max current 800mA
Dimensions: 48mm x 42mm
![enter image description here](https://www.openhardware.io//uploads/5844585be05bc30b20129722/image/Dual input charger_top.png "enter image title here")
This board combines battery management functionalities with power supply and UPS in one tiny package.