Lithium-ion battery pack monitoring circuit design

　　Intersil's ISL94203EVAL1Z is a kit that facilitates testing of the ISL94203 Li-ion battery pack monitoring and control IC. The ISL94203 monitors cell voltage, current and temperature. It converts cell voltage, current and temperature to 12-bit digital values, provides balancing control, and provides complete standalone battery operation. The ISL94203 default standalone operation can be overridden by an external microcontroller. A PC Graphical User Interface (GUI) supports the hooks required to monitor standalone operation with an external microcontroller and demonstrates operation.

　　Circuit Characteristics

　　Battery voltage monitoring supports Li-ion standalone pack control - no MCU required, multiple voltages and programmable detection/recovery, meets overvoltage, undervoltage, overcurrent and short circuit conditions, configuration maintenance/calibration registers, open battery connection detection, integrated charge/discharge FET drive circuit built-in, charge pump supports high-end n-channel FETs, balance using external FETs and internal state machine or external microcontroller, enters low power state after time of inactivity. Charge or discharge current detection resumes normal scan rate.

　　Functional Description

　　This IC is intended to be a standalone battery monitor, so it provides monitoring and protection functions without the use of an external microcontroller. The power control FETs of the section are positioned high by a built-in charge pump to drive the n-channel FETs. The current sense resistor is also high. Power is minimized across the board so that the section circuit is powered most of the time, extending battery life. At the same time, the RGO output stays on most of the time so any connected MCU can remain on most of the time. The ISL94203 includes: input level shifter to enable monitoring of battery stack voltage, 14-bit ADC converter, voltage readings are trimmed and results are saved to 12 bits, 1.8V voltage reference (0.8% accurate), .5V regulator, volt age hold during sleep

　　Power Path Connections

　　Figure 12 shows a main power path connected to the charge/discharge path.

　　Figure 13 shows connecting the separate charge/discharge paths.