Rainbow Electronics DS2745 - Manual (Page 6)

DS2745 Low-Cost I 2 C Battery Monitor
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DETAILED DESCRIPTION
Current is measured bidirectionally over a dynamic range of ±51.2mV with a resolution of 1.56 mV. Assuming a
15m W sense resistor, the current sense range is ±3.4A, with a 1 LSB resolution of 104mA. Current measurements
are performed at regular intervals and accumulated with each measurement to support accurate “coulomb
counting”. Each current measurement is reported with sign and magnitude in the two-byte Current register. The
Accumulated Current register (ACR) reports the coulomb count and supports a wide range of battery sizes. Battery
voltage measurements are reported in the two-byte Voltage register with 11-bit (4.88mV) resolution, and
Temperature is reported in the two-byte Temperature register with 0.125C resolution.
The DS2745 measurements can be used directly to provide accurate fuel gauging in typical use conditions, or
along with FuelPack™ algorithms to form a complete and accurate solution for estimating remaining capacity over
wide temperature and operating conditions.
Through its two wire I
2 C interface, the DS2745 allows a host system read/write access to the Status, Configuration
and Measurement registers. Additionally, the I 2 C slave address can be changed from the default after power up.
Figure 3. APPLICATION EXAMPLE
(1)
2.5V
150 W
1k W
R
SNS
(1)
5.6V
103
500 W
Protection IC
(Li+/Polymer)
1 Cell Li+
DS2745
SNS
VDD
PIO CTG
SCL VIN
VSS
SDA
PACK+
DATA
PACK -
102 102
150 W
CLOCK
(1) (1)
5.6V 5.6V
(1) Optional for 8kV/15kV ESD
FuelPack is a trademark of Dallas Semiconductor.