Datasheet

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FEATURES

16-Bit Bidirectional Current Measurement

1.56V LSB, ±51.2mV Dynamic Range

104A LSB, ±3.4A Dynamic Range (RSNS =

15m)

Current Accumulation Register Resolution

6.25Vhr LSB, ±204.8mVh Range

0.417mAhr LSB, ±13.65Ah Range

SNS

= 15m)

11-Bit Voltage Measurement

4.88mV LSB, 0V to 4.5V Input Range

11-Bit Temperature Measurement

0.125ºC Resolution, -20ºC to +70ºC

Industry Standard I

C Interface

Low Power Consumption:

Active Current:

70A typical, 100A max

Sleep Current:

1A typical, 3A max

BLOCK DIAGRAM

PIN CONFIGURATION

DESCRIPTION

The DS2745 provides current-flow, voltage, and

temperature measurement data to support battery-

capacity monitoring in cost-sensitive applications. The

DS2745 can be mounted on either the host side or

pack side of the application. Current measurement

and coulomb counting is accomplished by monitoring

the voltage drop across an external sense resistor,

voltage measurement is accomplished through a

separate voltage-sense input, and temperature

measurement takes place on-chip. A standard I

interface with software programmable address gives

the controlling microprocessor access to all data and

status registers inside the DS2745. A low-power sleep

mode state conserves energy when the cell pack is in

storage.

APPLICATIONS

Cellular

GPS

PDAs

Handheld Products

Table 1.

ORDERING INFORMATION

PART MARKING PIN-PACKAGE

DS2745U+

2745

MAX package

DS2745U+T&R

2745

DS2745U+ in Tape-and-Reel

+Denotes a lead(Pb)-free/RoHS-compliant package.

DS2745

Low-Cost I

C Battery Monito

www.maxim-ic.com



MAX

SDA

VDD

VIN

CTG

VSS

SNS

PIO

See Table 1 for Ordering Information.

19-4631

;

Rev 5/09

Summary of content (15 pages)

PAGE 1
9-4631; Rev 5/09 DS2745 2 Low-Cost I C Battery Monitor www.maxim-ic.com PIN CONFIGURATION FEATURES 16-Bit Bidirectional Current Measurement 1.56V LSB, ±51.2mV Dynamic Range 104A LSB, ±3.4A Dynamic Range (RSNS = 15m) Current Accumulation Register Resolution 6.25Vhr LSB, ±204.8mVh Range 0.417mAhr LSB, ±13.65Ah Range (RSNS = 15m) 11-Bit Voltage Measurement 4.88mV LSB, 0V to 4.5V Input Range 11-Bit Temperature Measurement 0.
PAGE 2
DS2745 Low-Cost I2C Battery Monitor ABSOLUTE MAXIMUM RATINGS* Voltage on All Pins Relative to VSS Operating Temperature Range Storage Temperature Range Soldering Temperature -0.3V to +6V -40°C to +85°C -55°C to +125°C See IPC/JEDECJ-STD-020A * This is a stress rating only and functional operation of the device at these or any other conditions above those indicated in the operation sections of this specification is not implied.
PAGE 3
DS2745 Low-Cost I2C Battery Monitor ±2 -20°C ≤ TA ≤ +70°C, 2.5V ≤ VDD ≤ 4.5V Input Resistance, VIN RIN Input Logic High: SCL, SDA, PIO Input Logic Low: SCL, SDA, PIO Output Logic Low: SDA, PIO Pulldown Current: SCL, SDA, PIO Input Capacitance: SCL, SDA CBUS SLEEP Timeout tSLEEP ±3 15 M 1.5 V VIH (Note 1) VIL (Note 1) 0.6 V VOL IOL = 4mA (Note 1) 0.4 V A 0.25 IPD (Note 3) 50 pF 2.2 S MAX UNITS 400 KHz 2-WIRE INTERFACE TIMING SPECIFICATIONS (VDD = 2.5V to 4.
PAGE 4
DS2745 Low-Cost I2C Battery Monitor Note 1: Note 2: Note 3: Note 4: Note 5: Note 6: Note 7: Note 8: Note 9: Note 10: Note 11: Note 12: All voltages are referenced to VSS. Offset specified after auto-calibration cycle and Current Offset Bias register (COBR) set to 00h. To properly enter sleep mode, SMOD=1, and the application should hold SDA and SCL low for longer than the maximum tSLEEP. NBEN = 0, Current Offset Bias Register (COBR) set to 00h, and Accumulation Bias Register (ABR) set to 00h.
PAGE 5
DS2745 Low-Cost I2C Battery Monitor PIN DESCRIPTION PIN SYMBOL FUNCTION 1 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 (IPD) for sensing disconnection. 2 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 (IPD) for sensing disconnection. 3 PIO General Purpose Input/Output.
PAGE 6
DS2745 Low-Cost I2C Battery Monitor 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.
PAGE 7
DS2745 Low-Cost I2C Battery Monitor POWER MODES The DS2745 operates in one of two power modes: active and sleep. While in active mode, the DS2745 operates as a high-precision battery monitor with voltage, temperature, current and accumulated current measurements acquired continuously and the resulting values updated in the measurement registers. Read and write access is allowed to all registers. In sleep mode, the DS2745 operates in a low-power mode with no measurement activity.
PAGE 8
DS2745 Low-Cost I2C Battery Monitor Figure 5. TEMPERATURE REGISTER FORMAT MSB—Address 0A 29 S 28 27 26 LSB—Address 0B 25 24 MSb 23 22 LSb 21 20 X X X X MSb X LSb Units: 0.125C “S”: sign bit, “X”: reserved CURRENT MEASUREMENT In the active mode of operation, the DS2745 continually measures the current flow into and out of the battery by measuring the voltage drop across a low-value current-sense resistor, RSNS, connected between the SNS and VSS pins.
PAGE 9
DS2745 Low-Cost I2C Battery Monitor CURRENT ACCUMULATION The Accumulated Current register (ACR) serves as an up/down counter holding a running count of charge stored in the battery. Current measurement results, plus a programmable bias value are internally summed, or accumulated, at the completion of each current measurement conversion period with the results displayed in the ACR. The ACR has a range of 0mVh to +409.6mVh with an LSb of 6.
PAGE 10
DS2745 Low-Cost I2C Battery Monitor CURRENT BLANKING The Current Blanking feature modifies current measurement result prior to being accumulated in the ACR. Current Blanking occurs conditionally when a current measurement (raw current + COBR) falls in one of two defined ranges. The first range prevents charge currents less than 100V from being accumulated. The second range prevents discharge currents less than 25V in magnitude from being accumulated.
PAGE 11
DS2745 Low-Cost I2C Battery Monitor Table 5.
PAGE 12
DS2745 Low-Cost I2C Battery Monitor 2-WIRE BUS SYSTEM The 2-Wire bus system supports operation as a slave only device in a single or multi-slave, and single or multimaster system. Up to 128 slave devices may share the bus by uniquely setting the 7-bit slave address. The 2-wire interface consists of a serial data line (SDA) and serial clock line (SCL). SDA and SCL provide bidirectional communication between the DS2745 slave device and a master device at speeds up to 400kHz.
PAGE 13
DS2745 Low-Cost I2C Battery Monitor Read/Write Bit The R/W bit following the slave address determines the data direction of subsequent bytes in the transfer. R/W = 0 selects a write transaction, with the following bytes being written by the master to the slave. R/W = 1 selects a read transaction, with the following bytes being read from the stave by the master. Bus Timing The DS2745 is compatible with any bus timing up to 400kHz. No special configuration is required to operate at any speed.
PAGE 14
DS2745 Low-Cost I2C Battery Monitor Write Data Protocol The write data protocol is used to write to register and shadow RAM data to the DS2745 starting at memory address MAddr. Data0 represents the data written to MAddr, Data1 represents the data written to MAddr + 1 and DataN represents the last data byte, written to MAddr + N. The master indicates the end of a write transaction by sending a STOP or Repeated START after receiving the last acknowledge bit.
PAGE 15
DS2745 Low-Cost I2C Battery Monitor REVISION HISTORY REVISION DATE 5/09 DESCRIPTION Changed the VDD maximum operating range in the Electrical Characteristics table to 4.5V. Added “VIN pin is limited to VDD voltage” text in the Voltage Measurement section. PAGES CHANGED 2, 3 7 15 of 15 Maxim cannot assume responsibility for use of any circuitry other than circuitry entirely embodied in a Maxim product. No circuit patent licenses are implied.