Mitsumi Electric Co., Ltd. has developed a protection IC of one-cell lithium ion lithium polymer secondary battery for smartphones and wearable devices. The MM3846 Series protection IC is built in with a high-side control circuit consisting of N_ch field effect transistors (FETs). It also has a built-in function for battery pack abnormal temperature detection. Thus, it contributes to safer battery charging as today’s battery packs for mobile devices have higher capacity and faster charging.

Call for Safer Batteries

In recent years, the battery capacity for smartphones and tablets has become higher. Also, the number of models supporting quick charging is increasing.

The increase in current due to rapid charging requires a highly accurate temperature protection function. This function utilizes the resistance change of an external negative temperature coefficient (NTC) thermistor, instead of the temperature protection using the conventional positive temperature coefficient (PTC). Some battery packs feature high-performance function such that their status can be monitored by a device through communication of information to the system.

In response to these market needs, the company has developed a protection IC with a built-in function of detecting abnormal temperature of a battery pack. Also, it has a built-in high-side control circuit consisting of N_ch FETs, causing little influence on communication. It enables safer charging of a battery by detecting the abnormal temperature of the battery pack. In addition, direct monitoring of cell voltage is possible using a networked device. This allows more accurate display of the remaining battery level.

Detailed Features

Specifically, the battery has temperature protection function that utilizes the resistance change of an external NTC thermistor. It has a built-in charge pump circuit for high side control consisting of N_ch FETs. It also feature a built-in cell overcharge, overdischarge, and overcurrent protection function.

The main specifications are as follows: overcharge detection voltage of 4.2 to 4.6V (5mV steps) with accuracy of ±15mV; overdischarge detection voltage of 2.0 to 3.0V (50mV steps) with accuracy of ±40mV; discharge overcurrent detection voltage of -10 to -150mV (1mV steps) with accuracy of ±3mV; charging overcurrent detection voltage of 10 to 150mV (1mV steps) with accuracy of ±4 mV; and short circuit detection voltage is -40 to -300mV (5mV steps) with accuracy of ±4mV. The battery protection IC has external dimensions of 1.66×1.06×0.36(H)mm and is available in WLSCP-8E/8F package.

The battery protection IC is designed for smartphones and tablets, wearable devices such as wireless earphones, and other mobile devices.