DS2745-DS2745U+ Fast Delivery |IC PHOENIX CO.,LIMITED

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DS2745-DS2745U+
Low-Cost I²C Battery Monitor
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
0.125ºC Resolution, -20ºC to +70ºC
Industry Standard I2C 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 I2C
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 I2C Battery Monitor

MAX
SDA
VDD
VIN
CTG
VSS SNS
PIO
SCL
See Table 1 for Ordering Information.
19-4631; Rev 5/09
DS2745 Low-Cost I2C Battery Monitor
ABSOLUTE MAXIMUM RATINGS*
Voltage on All Pins Relative to VSS -0.3V to +6V
Operating Temperature Range -40°C to +85°C
Storage Temperature Range -55°C to +125°C
Soldering Temperature 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. Exposure to absolute maximum rating conditions for extended periods of time may affect reliability.
RECOMMENDED DC OPERATING CONDITIONS
(2.5V  VDD  4.5V; TA = 0C to +70C.)
PARAMETER SYMBOL CONDITIONS MIN TYP MAX UNITS
Supply Voltage VDD (Note 1) +2.5 +4.5 V
Serial Data I/O Pin SDA (Note 1) -0.3 +5.5 V
Serial Clock Pin SCL (Note 1) -0.3 +5.5 V
Programmable I/O Pin PIO (Note 1) -0.3 +5.5 V
VIN Pin VIN (Note 1) -0.3 VDD +0.3 V
DC ELECTRICAL CHARACTERISTICS
(2.5V  VDD  4.5V; TA = 0C to +70C, unless otherwise noted.)
PARAMETER SYMBOL CONDITIONS MIN TYP MAX UNITS70 100
Active Current IACTIVE
VDD = 4.5V 105 A
Sleep-Mode Current ISLEEP SCL = SDA = VSS,
PIO = VSS 1 3 A
Current Resolution ILSB 1.56 V/R
Current Full-Scale
Magnitude IFS (Note 1) 51.2 mV/R
Current Offset IOERR (Note 2) -7.82 +12.5 V/R
Current Gain Error IGERR -1.0 +1.0 % of
reading
Accumulated Current
Resolution qCA 6.25 Vh/R
Accumulated Current
Offset qOERR VSNS = VSS, (Notes 4, 5) -188 +0 µVh/R
per day
Voltage Resolution VLSB 4.88 mV
Voltage Full-Scale VFS 0 4.992 V
Voltage Error VGERR (Note 12) -25 +25 mV
Temperature Resolution TLSB 0.125 °C
Temperature Error TERR -3 +3 ºC
Current Sample Clock
Frequency fSAMP 18.6 kHz
DS2745 Low-Cost I2C Battery Monitor ±2
-20°C ≤ TA ≤ +70°C,
2.5V ≤ VDD ≤ 4.5V ±3
Input Resistance, VIN RIN 15 M
Input Logic High:
SCL, SDA, PIO VIH (Note 1) 1.5 V
Input Logic Low:
SCL, SDA, PIO VIL (Note 1) 0.6 V
Output Logic Low:
SDA, PIO VOL IOL = 4mA (Note 1) 0.4 V
Pulldown Current: SCL,
SDA, PIO IPD 0.25 A
Input Capacitance: SCL,
SDA CBUS 50 pF
SLEEP Timeout tSLEEP (Note 3) 2.2 S
2-WIRE INTERFACE TIMING SPECIFICATIONS
(VDD = 2.5V to 4.5V, TA = -20C to +70C.)
PARAMETER SYMBOL CONDITIONS MIN TYP MAX UNITS
SCL Clock Frequency fSCL (Note 6) 0 400 KHz
Bus Free Time Between a
STOP and START Condition tBUF 1.3 µs
Hold Time (Repeated)
START Condition tHD:STA (Note 7) 0.6 µs
Low Period of SCL Clock tLOW 1.3 µs
High Period of SCL Clock tHIGH 0.6 µs
Setup Time for a Repeated
START Condition tSU:STA 0.6 µs
Data Hold Time tHD:DAT (Note 8, 9) 0 0.9 µs
Data Setup Time tSU:DAT (Note 8) 100 ns
Rise Time of Both SDA and
SCL Signals tR 20 + 0.1CB 300 ns
Fall Time of Both SDA and
SCL Signals tF 20 + 0.1CB 300 ns
Setup Time for STOP
Condition tSU:STO 0.6 µs
Spike Pulse Widths
Suppressed by Input Filter tSP (Note 10) 0 50 ns
Capacitive Load for Each
Bus
Line
CB (Note 11) 400 pF
SCL, SDA Input
Capacitance CBIN 60 pF
DS2745 Low-Cost I2C Battery Monitor
Note 1: All voltages are referenced to VSS.
Note 2: Offset specified after auto-calibration cycle and Current 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 tSLEEP.
Note 4: NBEN = 0, Current Offset Bias Register (COBR) set to 00h, and Accumulation Bias Register (ABR)
set to 00h.
Note 5: Parameters guaranteed by design.
Note 6: Timing must be fast enough to prevent the DS2745 from entering sleep mode due to SDA,SCL low
for period >
tSLEEP.
Note 7: fSCL must meet the minimum clock low time plus the rise/fall times.
Note 8: The maximum tHD:DAT has only to be met if the device does not stretch the LOW period (tLOW) of the
SCL
signal.
Note 9: This device 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 on SDA and SCL suppress noise spikes at the input buffers and delay the sampling instant.
Note 11: CBtotal capacitance of one bus line in pF.
Note 12: The first voltage measurement after writing the ACR or after device POR is not valid.
Figure 1. I2C Bus Timing Diagram
DS2745 Low-Cost I2C Battery Monitor
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 (IPD) 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 (IPD) 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 VSS and SNS.
5 VSS Device Ground. Connect to the negative terminal of the Li+ cell outside the cell
protection FETs. Connect the sense resistor between VSS 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 VDD Power-Supply Input. Connect to the positive terminal of the Li+ cell through a
decoupling network.
Figure 2. BLOCK DIAGRAM
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. 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 I2C interface, the DS2745 allows a host system read/write access to the Status, Configuration
and Measurement registers. Additionally, the I2C slave address can be changed from the default after power up.
Figure 3. APPLICATION EXAMPLE
(1)
2.5V
RSNS
(1)
5.6V103
Protection IC
(Li+/Polymer)
1 Cell Li+
DS2745
SNS
VDD
PIOCTG
SCLVIN
VSS
SDA
PACK+
DATA
PACK -
150CLOCK
(1)(1)
5.6V5.6V
(1) Optional for 8kV/15kV ESD
FuelPack is a trademark of Maxim Integrated Products, Inc.
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. Serial access to current,
accumulated current, and status/control registers is allowed in sleep mode if VDD > 2V.
The DS2745 operating mode transitions from SLEEP to ACTIVE when: SDA > VIH OR SCL > VIH
The DS2745 operating mode transitions from ACTIVE to SLEEP when:
SMOD = 1 AND (SDA < VIL AND SCL < VIL) for tSLEEP.
CAUTION: If SMOD = 1, pull-up resistors are required on SCL and/or SDA in order to ensure that the DS2745
transitions from SLEEP to ACTIVE mode when the battery is charged. If the bus is not pulled up, the DS2745
remains in SLEEP and cannot accumulate the charge current. This caution statement applies particularly to on a
battery that is charged on a standalone charger.
VOLTAGE MEASUREMENT
Battery voltage is measured at the VIN input with respect to VSS over a range of 0 to 4.992V (VIN pin is limited to
VDD voltage) and with a resolution of 4.88mV. The result is updated every 440ms and placed in the VOLTAGE
register in two’s compliment form. Voltages above the maximum register value are reported as 7FFFh.
Figure 4. VOLTAGE REGISTER FORMAT
MSB—Address 0C LSB—Address 0D
S 29 28 27 26 25 24 23 22 21 20 X X X X X
MSb LSb MSb LSb
“S”: sign bit(s), “X”: reserved Units: 4.88mV
The input impedance of VIN is sufficiently large (>15M) to be connected to a high impedance voltage divider in
order to support multiple cell applications. The pack voltage should be divided by the number of series cells to
present a single cell average voltage to the VIN input. Note that the first voltage measurement made after the
DS2745 is powered or after the ACR register is written will not be valid. The host should wait one measurement
cycle after either of these two conditions occur before reading voltage.
TEMPERATURE MEASUREMENT
The DS2745 uses an integrated temperature sensor to measure battery temperature with a resolution of 0.125°C.
Temperature measurements are updated every 440ms and placed in the Temperature Register in two’s
complement form.
DS2745 Low-Cost I2C Battery Monitor
Figure 5. TEMPERATURE REGISTER FORMAT
MSB—Address 0A LSB—Address 0B
S 29 28 27 26 25 24 23 22 21 20 X X X X X
MSb LSb MSb LSb
“S”: sign bit, “X”: reserved Units: 0.125C
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. The voltage sense range between SNS and VSS is ±51.2mV. Note that positive current values occur when
VSNS is less than VSS, and negative current values occur when VSNS is greater than VSS. Peak signal amplitudes up
to 102mV are allowed at the input as long as the continuous or average signal level does not exceed ±51.2mV over
the conversion cycle period. The ADC samples the input differentially at with an 18.6kHz sample clock and updates
the current register at the completion of each conversion cycle. Figure 6 describes the current measurement
register format and resolution. Charge currents above the maximum register value are reported at the maximum
value (7FFFh = +51.2mV). Discharge currents below the minimum register value are reported at the minimum
value (8000h = -51.2mV).
Figure 6. CURRENT REGISTER FORMATS
MSB—Address 0E LSB—Address 0F
S 214 213 212 211 210 29 28 27 26 25 24 23 22 21 20
MSb LSb MSb LSb
“S”: sign bit Units: 20 = 1.5625V/Rsns
Table 2. CURRENT RESOLUTION FOR VARIOUS RSNS VALUES
CURRENT RESOLUTION (1 LSB)
RSNS CONVERSION
TIME |VSS - VSNS| 20m 15m 10m 5m
3.5s 1.5625V 78.13A 104.2A 156.3A 312.5A
Table 3. CURRENT RANGE FOR VARIOUS RSNS VALUES
CURRENT INPUT RANGE
RSNS VSS - VSNS
20m 15m 10m 5m
±51.2mV ±2.56A ±3.41A ±5.12A ±10.24A
Every 1024th conversion, the ADC measures its input offset to facilitate offset correction. Offset correction occurs
approximately once per hour. The resulting correction factor is applied to the subsequent 1023 measurements.
During the offset correction conversion, the ADC does not measure the SNS to VSS signal. A maximum error of
1/1024 in the accumulated current register (ACR) is possible, however, to reduce the error, the current
measurement just prior to the offset conversion is displayed in the current register and is substituted for the
dropped current measurement in the current accumulation process. The error due to offset correction is typically

Partno	Mfg	Dc	Qty	Available	Descript
DS2745	MAXIM	N/a	5752	avai	Low-Cost I²C Battery Monitor
DS2745	DS	N/a	62	avai	Low-Cost I²C Battery Monitor
DS2745U+ \|DS2745U	DALLAS	N/a	213	avai	Low-Cost I²C Battery Monitor
DS2745U+ \|DS2745U	MAXIM	N/a	10	avai	Low-Cost I²C Battery Monitor