Shifting to a multicell battery stack and maintaining validated design
A solution that allows for improved efficiency of the backlight with the upgrade to a multi-cell battery stack and the reuse of the validated single-cell design is to use a front-end PMU. An integrated device such as the TPS65090, which has a high input voltage range (for example, 6 V to 17 V), a charger with power-path management, three step-down converters, two always-on LDOs, seven load switches and an I 2C interface, can stand between the multi-cell battery and the single-cell power system. This approach allows for the shift to a multi-cell battery stack solution by adding the front-end PMU and using an LED driver optimized for the higher voltage IC.
The front-end PMU can connect directly to the battery stack with the power-path and PMU charger functionality. This protects the system and controls charging the multi-cell battery stack using an AC adapter. The power-path, or system voltage, connects to the WLED driver and the frontend PMU switching converters input and LDOs, with outputs of 5 V, 3.3 V and a converter with adjustable output from 1.0 V to 3.3 V. Since these voltages are typical for single-cell battery systems, and the switching converters are capable of delivering a single-cell battery-like 4A continuous current, these front-end PMU outputs drive the downstream ICs in the existing single-cell design. Moreover, the TPS65090 has seven load switches, capable of reducing power consumption of disabled peripheral ICs down to 1 uA.