Operating Fuel Gauge bq20z7x/8x/9x and SMBus-Like bq24745/47/65 Chargers
The smart charger bq24747/765 is a high-efficiency, synchronous battery charger with an integrated input current comparator. This charger provides low component count for space constrained, multichemistry battery charging applications. SMBus input current, charge current, and input current digital-to-analog converters allow for very high regulation accuracies that the system power management microcontroller can easily program by using SMBus protocol.
The bq20z7x/8x/9x, SBS-compliant gas gauge integrated circuit (IC), incorporating patented Impedance Track technology, is designed for battery-pack or in-system installation. It measures and maintains an accurate record of available charge in Li-ion or Li-polymer batteries using its integrated high-performance analog peripherals. It monitors capacity change, battery impedance, open-circuit voltage, and other critical parameters of the battery pack, and reports the information to the system host controller over a SMBus.
The charger IC (bq24747/765) and gas gauge IC (bq20z7x/8x/9x) are both SBS compliant. The ChargeCurrent() register address is 0x14. The ChargerVoltage() register address is 0x15. The charger IC operates as a slave. Control input is received from the gas gauge IC through the SMBus. The gas gauge IC operates as master with broadcasts enabled. It broadcasts the ChargeCurrent() and ChargeVoltage() command to the charger IC. When the charger IC gets the two commands, it starts the charger. In this system, no extra host controller is required for the charger IC. It saves the total cost or the total system software resource.