Texas Instruments bq25155 Battery Charge Management IC unites the most common functions for wearable and portable devices. These functions comprise a charger, a regulated output voltage rail for system power, ADC for battery and system monitoring, an LDO, and push-button controller. The IC unites a linear charger with PowerPath that allows swift and accurate charging for small batteries while giving a regulated voltage to the system. The regulated system voltage (PMID) output can be configured through I2C based on the recommended operating condition of downstream IC’s and system loads for optimal system operation.
The device maintains charge current up to 500mA and supports termination current down to 0.5mA for maximum charge. The battery is charged employing a standard Li-Ion charge profile with three phases: pre-charge, constant current and constant voltage regulation.
The device incorporates advanced power path management and control that enables the device to give power to the system while charging the battery even with poor adapters. The host can also control the power path through I2C, enabling it to disconnect the input adapter and battery without actually excluding them. The single push-button input removes the requirement for a separate button controller IC lessening the total solution footprint. The push-button input can be utilised for wake functions or to reset the system.
A 16-bit ADC allows accurate battery voltage monitoring and can be used to facilitate a low Iq gauging to monitor battery health. It can also be utilised to measure the battery temperature employing a thermistor connected to the TS pin as well as external system signals through a pin. The low quiescent current during operation and shutdown allows maximum battery life. The input LDO output voltage, current limit, charge current, and other parameters are programmable within the I2C interface giving the device a very flexible charging solution.
A voltage-based JEITA compatible (or standard HOT/COLD) battery pack thermistor monitoring input is provided to monitor battery temperature. This battery pack automatically adjusts charge parameters to stop the battery from charging outside of its safe temperature range. The temperature thresholds are programmable through I2C, enabling the host to customise the thermal charging profile. The charger is optimised for 5V USB input, with 20V absolute maximum tolerance to resist line transients. The device also combines a linear regulator to give a quiet rail for radios or processors and can be separately sourced and controlled through I2C.