Design Of A High-accuracy,multi-mode Li-ion Battery Aptitude Charge Management Chip

With the development of IC technology, the amount and type of handheld devices is increasing, and as the core of handheld devices, batteries are expected to be given has become increasingly high, the shortage of traditional storage batteries began to emerge. Emerging energy lithium-ion batteries for its high specific energy, no pollution, the advantages of large capacity, long cycle life, known as the 21 st century the development of the ideal energy and become the mainstream of the energy storage devices on the market today. However, when using lithium batteries also have security issues of concern: overcharge and high temperature will cause the lithium batteries have a risk of explosion; over-discharge will reduce the life of lithium-ion batteries and even damage the lithium battery. During the lithium battery charging and discharging its take certain protective measures are very necessary, therefore, high reliability, high precision, safe and fast battery charging management chip research is of great importance.This design adopts the CSMC 0.5 um BCD process, according to the working principle of type Buck switch converter, analysis and design for more than a high precision model of lithium battery intelligent charging management chip. In this paper, the design of lithium battery management chip for lithium batteries using a three-stage charging mode: precharge trickle mode, constant current mode and constant voltage mode. Due to the trickle charging makes the system operated in discontinuous conduction mode(DCM), while the constant current charging system is operating in continuous conduction mode(CCM), in order to improve the transient response to the change of the power supply voltage and load capacity and the conversion efficiency of the system, the design uses peak current mode pulse modulation mode(PFM-PWM) control mode. To be able to adapt to a wide input voltage range, introduces a slope compensation technology to increase the load ability of the system; The chip maximum programmable charge current up to 2A and charging time can be set in a external security, achieved with the user’s interactive management; By trimming technology enables simultaneous battery charging termination voltage accuracy up to ± 0.75%, and the external series set on a section or two series lithium battery to charge. This design is also based on safety norms Battery Association of Japan promulgated integrated NTC battery temperaturemonitoring in real-time to adjust the charging current and charging termination voltage charging mode. In addition, the chip integrates cycle-by-cycle current limit protection circuit, over temperature protection circuitry, battery overcharge protection circuit, bad battery detection, improved the charging rate and ensured the safety of the lithium battery at the same time.The article first introduces the development process of the lithium battery, lithium battery charging principles and charging methods, and applications on the market today are more charging management chip, and then describes the principles and characteristics of Buck switching converter, compared the advantages and disadvantages of current control mode and the voltage control mode, and then based on the basic of Buck DC_DC topology for the stability of the system are analyzed. Finally on the basis of the described in this article, designed the overall circuit. This paper mainly analyzes the bandgap reference circuit, oscillator and slope compensation circuit, NTC battery protection circuit, constant current/constant voltage operational amplifier circuit and charging mode switch module. Under the premise of minimizing the overall design of the peripheral device circuit as a whole.Finally, this paper design the circuit on the platform of cadence’s simulation environment, simulation of the situation at different input voltages, different process parameters, different working environment temperature and other conditions on the use of voltage source simulated battery charging, The simulation results are to meet the requirements of the design specifications, has been out tapeout.