MAX1811 Lithium Battery Charger Production

1 Features
MAX1811 does not require microprocessor control, and the maximum charging voltage can be set to 4.1 V or 4.2 V by pins, with a maximum error of 0.5%.
MAX1811 can set the battery charging current to 100mA or 500mA through the logic control circuit, which meets the USB current standard. MAX1811 works in linear mode, does not require external inductors, and the built-in MOSFET power switch effectively saves the size of the circuit board.
When using the USB port power supply to charge the battery, for low-power USB ports, the SETI terminal potential of the MAX1811 chip should be pulled low, and its charging current is set to 100mA. For high-power USB ports, the SETI pin of the MAX1811 chip should be connected to a high level, and the charging current is set to 500mA; connect the 5ETV terminal to a high level or a low level, and the charging voltage of the lithium battery is set to 4.2 V or 4.1 V respectively. The CHG terminal of MAX1811 allows the chip to light up the LED during charging.

2 Pin Function
The MAX1811 uses an enhanced thermal 8-pin SO package, which allows a power dissipation of 1.4 W: In addition, the MAX1811 also has an internal thermal protection diode, which reduces the cost and size of the charger. The MAX1811 pin functions are shown in the following table.

3 MAX1811 Lithium Battery Charging Control Circuit

The charging current of this circuit is available in two gears: 100mA (when switch SB is disconnected in the figure) and 500mA (when switch S is closed in the figure). When the circuit allows the MAX1811's first pin to be connected as shown in the figure, the maximum charging voltage is 4.2V; when the first pin is connected to the negative end of the power supply, the maximum charging voltage is 4.1V. Once the maximum charging voltage is reached, the charging current decreases sharply and maintains the maximum charging voltage unchanged. In the figure, VD1 is used as a power indicator, and VD2 is used as a charging indicator. The light is on when charging is in progress, and the light is off when charging is completed.