BQ27750 Datasheet, PDF (16/34 Pages) Texas Instruments – Impedance Track Battery Gas Gauge and Protection Solution for 1-Series Cell Li-Ion Battery Packs

bq27750
SLUSCM7 – JUNE 2017
www.ti.com
7.3 Feature Description
7.3.1 Battery Parameter Measurements
The bq27750 device measures cell voltage and current simultaneously, and also measures temperature to
calculate the information related to remaining capacity, full charge capacity, state-of-health, and other gauging
parameters.
7.3.1.1 bq27750 Processor
The bq27750 device uses a custom TI-proprietary processor design that features a Harvard architecture and
operates at frequencies up to 4.2 MHz. Using an adaptive, three-stage instruction pipeline, the bq27750
processor supports variable instruction length of 8, 16, or 24 bits.
7.3.2 Coulomb Counter (CC)
The first ADC is an integrating converter designed specifically for coulomb counting. The converter resolution is a
function of its full-scale range and number of bits, yielding a 3.74-µV resolution.
7.3.3 CC Digital Filter
The CC digital filter generates a 16-bit conversion value from the delta-sigma CC front end. Its FIR filter uses the
LFO clock output, which allows it to stop the HFO clock during conversions. New conversions are available every
250 ms while CCTL[CC_ON] = 1. Proper use of this peripheral requires turning on the CC modulator in the AFE.
7.3.4 ADC Multiplexer
The ADC multiplexer provides selectable connections to the VCx inputs, TS1 inputs, internal temperature sensor,
internal reference voltages, internal 1.8-V regulator, PACK input, and VSS ground reference input. In addition,
the multiplexer can independently enable the TS1 input connection to the internal thermistor biasing circuitry, and
also enables the user to short the multiplexer inputs for test and calibration purposes.
7.3.5 Analog-to-Digital Converter (ADC)
The second ADC is a 16-bit delta-sigma converter designed for general-purpose measurements. The ADC
automatically scales the input voltage range during sampling based on channel selection. The converter
resolution is a function of its full-scale range and number of bits, yielding a 38-µV resolution. The default
conversion time of the ADC is 31.25 ms, but is user-configurable down to 1.95 ms. Decreasing the conversion
time presents a tradeoff between conversion speed and accuracy, as the resolution decreases for faster
conversion times.
7.3.6 ADC Digital Filter
The ADC digital filter generates a 24-bit conversion result from the delta-sigma ADC front end. Its FIR filter uses
the LFO clock, which allows it to stop the HFO clock during conversions. The ADC digital filter is capable of
providing two 24-bit results: one result from the delta-sigma ADC front end and a second synchronous result
from the delta-sigma CC front end.
7.3.7 Internal Temperature Sensor
An internal temperature sensor is available on the bq27750 device to reduce the cost, power, and size of the
external components necessary to measure temperature. It is available for connection to the ADC using the
multiplexer, and is ideal for quickly determining pack temperature under a variety of operating conditions.
7.3.8 External Temperature Sensor Support
The TS1 input is enabled with an internal 18-kΩ (typical) linearization pull-up resistor to support the use of a 10-
kΩ (25°C) NTC external thermistor, such as the Semitec 103AT-2. The NTC thermistor should be connected
between VSS and the individual TS1 pin. The analog measurement is then taken via the ADC through its input
multiplexer. If a different thermistor type is required, then changes to configurations may be required.
16
Submit Documentation Feedback
Product Folder Links: bq27750
Copyright © 2017, Texas Instruments Incorporated