The Design Of High Input Voltage Charging IC For Single-cell Li-Ion Batteries

Base on consideration of environment protection and reusable, Li-ion battery is takingthe top1in portable application because of excellent charging/discharging performance andenvironmentally friendly. Li-ion has its drawbacks: it is fragile. So the performance andlongevity of batteries are highly depended on the quality of the chargers. The purpose of thispaper is to design a high efficiency, safety and intelligent battery charging IC to secure theLi-ion batteries’ performance.The IC uses8-lead2X3UDFN package, wafer process is0.28um CMOS technology ofFreescale. The IC integrates most of important functions: trickle charging for a deeplydischarged battery, constant-current (CC)/constant-voltage (CV) charge modes, end ofCharge and Recharge modes; an internal timer for termination to prevent charging a failedbattery; charger current thermal fold-back for thermal protection, and smart batteryconnection verification to prevent charging in case there is no battery connected. Because ofhigh integration, No external FET, diode¤t sense resistor are needed. The onlyneeded external components are few: dual-color LED which can be used as status indicator, anegative temperature coefficient (NTC) thermistor circuit for setting the charge temperaturewindow, and two decoupling capacitors.The paper firstly introduces the batteries’ features, developing trend, and comparison ofcharging ICs, then one chapter is used to discuss about the IC’s basic functions and theory ofeach blocks. Following this, one chapter is used to describe the design target, specificelectrical parameters, and includes the top level circuit topology and analysis for all sub-modules. Cadence simulation is done as well to analyze the design target and parameter.Finally, the last chapter discusses fab process, assembly process, test results and reliabilityperformance for the final product.