DS2745U+ Datasheet DS2745U+ | P4-P6

DS2745 Low-Cost I

C Battery Monitor

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Note 1:

All voltages are referenced to V

Note 2:

Offset specified after auto-calibration cycle and Curre

nt Offset Bias register (COBR) set to 00h.

Note 3:

To properly enter sleep mode, SMOD=1, and the application should hold SDA and SCL low for longer

than the maximum t

SLEEP

Note 4:

NBEN = 0, Current Offset Bias Re

gister (COBR) set to 00h, and Accumulation Bias Register (ABR)

set to 00h.

Note 5:

Parameters guaranteed by design.

Note 6:

Timing mu

st be fast enough to prevent the DS2745 from entering sleep mode due to SDA,SCL low

for period >

SLEEP

Note 7:

SCL

must meet the minimum clock low time plus the rise/fall times.

Note 8:

The maximum t

HD:DAT

has only to be met if the device does not stretch the LOW period (t

LOW

) of the

SCL

signal.

Note 9:

This devi

ce internally provides a hold time of at least 100 ns for the SDA signal (referred to the

VIHmin of

the SCL signal) to bridge the undefined region of the falling edge of SCL.

Note 10:

Filters o

n SDA and SCL suppress noise spikes at the input buffers and delay the sampling instant.

Note 11:

total capacitance of one bus line in pF.

Note 12:

The first volta

ge measurement after writing the ACR or after device POR is not valid.

Figure 1. I

C Bus Timing Diagram

DS2745 Low-Cost I

C Battery Monitor

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PIN DESCRIPTION

PIN SYMBOL FUNCTION

SCL

Serial Clock Input. 2-Wire clock line. Input only. Connect this pin to the CLOCK

terminal of the battery pack. Pin has an internal pulldown (I

) for sensing

disconnection.

SDA

Serial Data Input/Output. 2-Wire data line. Open-drain output driver. Connect this pin

to the DATA terminal of the battery pack. Pin has an internal pulldown (I

) for sensing

disconnection.

PIO

General Purpose Input/Output. Open-drain output driver with input sense. Connect

to a pull up resistor for bidirectional operation.

SNS

Sense Resistor Connection. Connect to the negative terminal of the battery pack.

Connect the sense resistor between V

and SNS.

5 V

Device Ground. Connect to the negative terminal of the Li+ cell outside the cell

protection FETs. Connect the sense resistor between V

and SNS.

CTG

Connect to Ground. Connect to the negative terminal of the Li+ cell outside the cell

protection FETs.

VIN

Voltage Sense Input. The voltage of the Li+ cell is monitored through this input pin.

8 V

Power-Supply Input. Connect to the positive terminal of the Li+ cell through a

decoupling network.

Figure 2. BLOCK DIAGRAM

DS2745 Low-Cost I

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V. Assuming a

15m sense resistor, the current sense range is ±3.4A, with a 1 LSB resolution of 104A. 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

C interface, the DS2745 allows a host system read/write access to the Status, Configuration

and Measurement registers. Additionally, the I

C slave address can be changed from the default after power up.

Figure 3. APPLICATION EXAMPLE

(1)

2.5V

150

SNS

(1)

5.6V

103

500

Protection IC

(Li+/Polymer)

1 Cell Li+

DS2745

SNS

VDD

PIO

CTG

SCL

VIN

VSS

SDA

PACK+

DATA

PACK -

102 102

150

CLOCK

(1)(1)

5.6V 5.6V

(1) Optional for 8kV/15kV ESD

FuelPack is a trademark of Maxim Integrated Products, Inc.

P1-P3 P4-P6 P7-P9 P10-P12 P13-P15

DS2745U+

Mfr. #:

Buy DS2745U+

Manufacturer:

Maxim Integrated

Description:

Battery Management I2C Battery Monitor Fuel Gauge

Lifecycle:

New from this manufacturer.

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DS2745U+