bq20z65-R1

SLUS990 – DECEMBER 2009

www.ti.com

CONFIGURATION

Oscillator Function

The bq20z65-R1 fully integrates the system oscillators therefore, no external components are required for this

feature.

System Present Operation

The bq20z65-R1 periodically verifies the PRES pin and detects that the battery is present in the system via a low

state on a PRES input. When this occurs, the bq20z65-R1 enters normal operating mode. When the pack is

removed from the system and the PRES input is high, the bq20z65-R1 enters the battery-removed state,

disabling the charge, discharge, and ZVCHG FETs. The PRES input is ignored and can be left floating when

non-removal mode is set in the data flash.

BATTERY PARAMETER MEASUREMENTS

The bq20z65-R1 uses an integrating delta-sigma analog-to-digital converter (ADC) for current measurement, and

a second delta-sigma ADC for individual cell and battery voltage, and temperature measurement.

Charge and Discharge Counting

The integrating delta-sigma ADC measures the charge/discharge flow of the battery by measuring the voltage

drop across a small-value sense resistor between the SR1 and SR2 pins. The integrating ADC measures bipolar

time, using an internal counter. The fundamental rate of the counter is 0.65nVh.

Voltage

The bq20z65-R1 updates the individual series cell voltages at one second intervals. The internal ADC of the

bq20z65-R1 measures the voltage, scales and calibrates it appropriately. This data is also used to calculate the

impedance of the cell for the Impedance Track™ gas-gauging.

Current

The bq20z65-R1 uses the SRP and SRN inputs to measure and calculate the battery charge and discharge

current using a 5m

Ω to 20mΩ typ. sense resistor.

Wake Function

The bq20z65-R1 can exit sleep mode, if enabled, by the presence of a programmable level of current signal

across SRP and SRN.

Auto Calibration

The bq20z65-R1 provides an auto-calibration feature to cancel the voltage offset error across SRN and SRP for

maximum charge measurement accuracy. The bq20z65-R1 performs auto-calibration when the SMBus lines stay

low continuously for a minimum of a programmable amount of time.

Temperature

The bq20z65-R1 has an internal temperature sensor and 2 external temperature sensor inputs, TS1 and TS2,

used in conjunction with two identical NTC thermistors (default are Semitec 103AT) to sense the battery

environmental temperature. The bq20z65-R1 can be configured to use the internal temperature sensor or up to 2

external temperature sensors.

16

Submit Documentation Feedback

Copyright © 2009, Texas Instruments Incorporated

Product Folder Link(s): bq20z65-R1