Battery temperature monitoring

BQ2057 by measuring the TS and VSS pins the voltage between the battery temperature to realize a continuous monitoring of the thermistor used as temperature sensors, and through resistor divider, as shown in Figure 3-1. Divider resistance is calculated according to parameters.laptop battery BQ2057 the voltage within the V (TS1) and V (TS2) threshold voltage comparator to decide whether to allow charging. As the outer part of the pressure and threshold voltage within the department are VCC as a reference to ensure the temperature detection circuit VCC from the work of the power fluctuations. When the TS pin connected to VCC or VSS, you can charge against BQ2057 function.

2.4 Charge Status Indicator

BQ2057 through the tri-state STAT pin reporting the current charge status: Charging state of high, charging the completion of low-level, temperature, high impedance fault or sleep state. When the STAT pin with a single LED or dual LED reverse connected, it can achieve the charge status of the LED instructions STAT mouth can also be micro-controller interface with the equipment, micro-controller by identifying the mouth STAT
Three states to achieve intelligent management of devices.

3. Typical charger circuit desig

BQ2057-designed charger circuit using simple, widely used in portable electronic systems, IBM ThinkPad X41 Tablet Battery, IBM ThinkPad X60 Battery,the current power management for portable electronic products, compact design makes sense.

BQ2057 designed using rechargeable lithium batteries can be realized on a circuit or two rechargeable lithium battery, the working power supply DC + rechargeable lithium battery pack according to the voltage options, recommended operating voltage 4.5V ~ 18V, battery positive terminal voltage PACK + access BAT pin,IBM Laptop Battery TS-pin test battery thermistor NTC resistor divider after the adoption of the partial pressure value, thereby to determine the temperature is normal, BQ2057 can be designed by a PNP transistor or a P-channel MOSFET, charge, should be met in the choice power requirements, using PNP transistor charging circuit see Figure 3-1, using P-channel MOSFET, the charging circuit see Figure 3-2.

4. Conclusion
In our design of a portable electronic device, select the BQ2057W chip design equipment 7.2V lithium-ion battery charging circuit, the charging circuit is very simple, the whole charging process and the status display by BQ2057 individual achievement, the entire power management module is simple and reliable , the charger circuit for the lithium battery requirements related to the electronic system designed to be valuable
MAX1811 Lithium Battery Charge Controller2009-09-20 14:15Maxim MAX1811 is a USB interface produced by a single lithium battery charge controller, which can be powered directly from the USB port, or by other external power supply, power supply voltage up to +6.5 V.
1 Features
MAX1811 without microprocessor control, the maximum charge voltage pin can be set to 4.1 V or 4.2 V, the maximum error is 0.5%.
MAX1811 to charge the battery current can be set to logic control circuits 100mA or 500mA, in line with the current USB standard. MAX1811 works in linear mode without an external inductor, the built-in MOSFET power switch and effective to save the circuit board size.
When using U-port power to recharge the battery department, when, for low-power USB port, should MAX1811 chip SETI potential down side, IBM ThinkPad X60 Battery, the charging current is set to 100mA, for high-power USB port, should be cited MAX1811 chip SETI Then feet high, this time the charge current is set to 500mA; will 5ETV terminating high or low access, lithium battery charging voltage were set to 4.2 V or 4.1 V. MAX1811 allows chip in the CHG-side lit during charging LED.

2 Pin Function
MAX1811 uses a thermally enhanced 8-pin SO package, allowing power dissipation 1.4 W: In addition,IBM ThinkPad X41 Tablet Battery, IBM ThinkPad X60 Battery, MAX1811 also features internal thermal protection diodes, thereby reducing the cost and size of the charger. MAX1811 pin functions as indicated below.

Pin No. Pin Name Pin Function
1 SELV The battery voltage selector terminal
2 SETI Charge current setting terminal
3 GND Ground terminal
4 IN Supply voltage input
5 BATT Battery voltage detection input, usually right to take a 1.5uF capacitor
6 GND Ground terminal
7 EN Enable control terminal
8 / CHG Charge status indication signal output terminal

3 MAX1811 Li-ion battery charge control circuit

Charge current of the circuit there is 100mA (figure SB disconnect switch), 500mA (when the figure switch S is closed) two block to choose from. MAX1811 Circuit allowed the first figure connected by a pin, the maximum charge voltage of 4.2V;IBM ThinkPad X41 Tablet Battery, the first one foot and the power to connect the negative side, the maximum charge voltage of 4.1V. Once you reach the maximum charge voltage, the charge current to a sharp decline, and maintain the highest charge voltage constant. The figure, VD1 as the power instructions, VD2 as charging instructions, lights say they are charging, lights turned off and the end of that charge.