This is a breakout PCB for the MAX17043 single cell Li-Poly/Li-Ion fuel gauge. Determining the state of charge for a Li-Poly battery can be very difficult to determine due to the relatively flat discharge profile. Using a 2-Wire (I2C) interface, you can get the relative state of charge(SOC) displayed as a percentage. The board can also generate an external interrupt to alert the user if the battery charge falls below a "programmable" value of 1 - 32%. This is a useful feature if you don't want to have to continually poll the battery, just program an interrupt routine for low battery.
The board features 2 JST connectors for connecting the battery. The battery can be plugged into either connector. The second connector can be used as a bypass to the rest of circuit if you are placing the board in-line to an existing design. Since the board is powered by the battery the VDD pin must remain floating. It is possible to power the board from a 3.3/5 volt supply instead of using the battery but you will need to remove the solder from SJ1 first and then connect an external supply to VDD. There is no value added in doing this but the option is available if need be. Also please be sure to connect the battery using the correct polarity as there is no reverse voltage protection built in which means you could damage the IC and also battery.
The board is not affected by an external charging circuit, as a matter of fact you can monitor the battery SOC while it is charging to help determine how long until a full charge is reached.
NOTE ABOUT SOC READING AT FULL CHARGE
A couple of people had requested I look into the calibration procedure as described in the datasheet because they were getting SOC readings around 1-2% above or below the 100% level at full charge. Unfortunately Maxim was reluctant to provide details on how the configuration register can be adjusted. I decided to try different settings in the configuration register to come up with a calibration routine but was unable to produce significant enough variations in the final SOC reading to make an impact. After more testing I found that the charging circuit that is used seems to play the biggest role on the final SOC reading. I tested two different charging circuits and was able to charge the same battery to only 98% on one and a little over 101% on another.
- Single cell Li-Poly/Li-Ion fuel gauge
- Host-side or battery-side fuel gauging
- Battery SOC units displayed as a percentage down to 1/256%
- Battery voltage level also available
- No offset accumulation on measurement
- No full-to-empty battery relearning necessary
- No sense resistor required
- External alarm/interrupt for low-battery warning
- I2C interface up to 400kHz
- Powered directly from battery
- 5 volt tolerant IO
- Low power consumption (50uA)
- On-board JST connectors
- RoHS compliant