Rainbow Electronics DS2741 User Manual

General Description

The DS2741 current monitor/accumulator is a complete
current-sensing, measuring, and accumulation device
tailored for cost-sensitive, battery-powered applications
in a small 3mm x 3mm TDFN package. As a result, the
DS2741 is a key component in battery-charge control
and remaining capacity-estimation applications.

Through its I2C interface, the DS2741 gives the host
system access to current measurement and accumula­tion registers. The 7-bit slave address is factory pro­grammable, allowing up to 128 devices to be individually
addressed by the host system.

Applications

Cell Phones

PDAs

Battery Monitor/Rechargers

Features

♦ Complete, Low-Cost, Integrated Current-Sensing

and Accumulation Solution with Serial Digital
Output

♦ On-Board 38mΩ Sense Resistor

♦ Current Measurement:

Signed 10-Bit Bidirectional Measurement
±2.5A Dynamic Range
1% Error at +25°C
2% Error Over Temperature

♦ Current Accumulation:

0.247mAhr LSB
±8.1Ahrs Full-Scale Range

♦ Industry-Standard I

2

C Interface with Factory-

Programmable Slave Address

♦ 2.5V to 4.5V Single-Supply Operation

♦ Low-Power Consumption:

Active Current: 60µA (typ)
Sleep Current: 1µA (typ)

♦ -20°C to +70°C Operating Range

♦ 14-Pin TDFN (3mm x 3mm x 0.8mm)

DS2741

Current Monitor and Accumulator with

Integrated Sense Resistor

________________________________________________________________

Maxim Integrated Products

1

Pin Configuration

Ordering Information

DS2741

2.2kΩ

1.8V

2.2kΩ

0.1μF

RS+

GND

SLP

V

CC

RS-

SDA

SCL

DC-DC

CONVERTER

Li +

BATTERY

MICROPROCESSOR

CHARGER/

LOAD

Typical Operating Circuit

Rev 0; 8/08

For pricing, delivery, and ordering information, please contact Maxim Direct at 1-888-629-4642,
or visit Maxim’s website at www.maxim-ic.com.

+

Denotes a lead-free/RoHS-compliant package.

T = Tape and reel.

*

EP = Exposed pad.

PART TEMP RANGE PIN-PACKAGE

DS2741N+ -20°C to +70°C 14 TDFN-EP*

DS2741N+T -20°C to +70°C 14 TDFN-EP*

RS-

12

DS2741

245

3

RS+

TDFN

GND

SCL

DNC

9

8

EP*

6

7

V

CC

TOP VIEW

*EXPOSED PAD

RS- RS- SLP

RS-

13 11 10

14

+

1

RS+ RS+ SDA

RS+

DS2741

Current Monitor and Accumulator with
Integrated Sense Resistor

2 _______________________________________________________________________________________

ABSOLUTE MAXIMUM RATINGS

RECOMMENDED OPERATING CONDITIONS

(TA= -20°C to +70°C.)

Stresses beyond those listed under “Absolute Maximum Ratings” may cause permanent damage to the device. These are stress ratings only, and functional
operation of the device at these or any other conditions beyond those indicated in the operational sections of the specifications is not implied. Exposure to
absolute maximum rating conditions for extended periods may affect device reliability.

Voltage Range on VCCRelative to GND ...............-0.5V to +6.0V

Voltage Range on SDA, SCL,

RS+, RS-, SLP Relative to GND.....-0.5V to (V

CC

+ 0.5V), not to

exceed +6.0V

Continuous Internal Sense Resistor Current ......................±2.7A

Pulsed Internal Sense Resistor

Current ..................................±10A for <100µs/s, <1000 pulses

Operating Temperature Range ...........................-20°C to +70°C

Storage Temperature Range .............................-55°C to +125°C

Soldering Temperature...........................Refer to the IPC/JEDEC

J-STD-020 Specification.

DC ELECTRICAL CHARACTERISTICS

(2.5V ≤ VCC≤ 4.5V, TA= -20°C to +70°C.)

Supply Voltage VCC (Note 1) 2.5 4.5 V

Input Logic-High: SCL, SDA VIH 1.5 V

Input Logic-Low: SCL, SDA VIL 0.4 V

Input Logic-High: SLP V

Input Logic-Low: SLP V

Power-Up Ramp Time from
0V to V

PARAMETER SYMBOL CONDITIONS MIN TYP MAX UNITS

IH

IL

t

25 ms

CCMI N

RAMP

0.7 x
V

CC

V

0.3 x
V

CC

V

Active Current I

Sleep-Mode Current I

Output Logic-Low: SDA VOL IOL = 4mA (Note 1) 0.4 V

Internal Current-Sense Re sis tor
Value

Current Resolution I

Current Ful l-Scale Magnitude IFS (Note 2) 2.54 2.7 A

Current-Sense Accuracy at +25°C ATL I

Current-Sense Accuracy from
0°C to +70°C

Current Sampling Rate t

Accumulator Resolution qCA 0.247 mAh

Internal Time-Base Accuracy

Current-Sense Offset Mea sured w ith RS+ and RS- shorted -10 +10 mA

PARAMETER SYMBOL CONDITIONS MIN TYP MAX UNITS

ACTIVE

SLEEP

R

SNS

LSB

A

TL

CSR

t

ERR1

t

ERR2

SLP = SCL = SDA = VCC 60 90 μA
SLP = 0V 1 2 μA

+25°C 38 45 m

2.64 mA

at 1.5A ±1 ±2 %

SENSE

I

(Note 3) 200 μs

(Note 4) ±1 ±3

(Note 4) ±6.5

at 1.5A ±2 ±4 %

SENSE

%

DS2741

Current Monitor and Accumulator with

Integrated Sense Resistor

_______________________________________________________________________________________ 3

TEMPERATURE SENSOR CHARACTERISTICS

(VCC= +2.5V to +4.5V, TA= -20°C to +70°C, unless otherwise noted.)

AC ELECTRICAL CHARACTERISTICS: I2C INTERFACE

(2.5V ≤ VCC≤ 4.5V, TA= -20°C to +70°C, timing referenced to V

IL(MAX)

and V

IH(MIN)

. See Figure 4.)

Note 1: All voltages are referenced to GND. Currents entering the IC are specified positive and currents exiting the IC are negative.
Note 2: Compensation of the internal sense resistor value for initial tolerance and temperature coefficient of -20°C to +70°C can

reduce the maximum reportable magnitude to 2.5A.

Note 3: Current sampling ceases for 2.5ms every 144ms to allow the ADC to measure temperature.
Note 4: Typical value for t

ERR1

is specified at 3.6V and +25°C, max value is specified for 0°C to +50°C. Max value for t

ERR2

is

specified for -20°C to +70°C.

Note 5: Interface timing shown is for fast-mode (400kHz) operation. This device is also backward compatible with standard-mode

I

2

C timing.

Note 6: C

B

—Total capacitance of one bus line in pF; timing referenced to 0.1 x VCCand 0.9 x VCC.

Temperature Error ±5 °C

PARAMETER SYMBOL CONDITIONS MIN TYP MAX UNITS

SCL Clock Frequenc y f

Bus Free Time Between STOP
and START Conditions

Hold Time (Repeated) START
Condition

Low Period of SCL t

High Period of SCL t

Data Hold Time t

Data Setup Time t

START Setup Time t

SDA a nd SCL R i se Time tR (Note 6)

SDA and SCL Fall Time tF (Note 6)

STOP Setup Time t

SDA a nd SCL Capacit i ve
Loading

PARAMETER SYMBOL CONDITIONS MIN TYP MAX UNITS

(Note 5) 0 400 kHz

SCL

t

1.3 μs

BUF

t

0.6 μs

HD:STA

1.3 μs

LOW

0.6 μs

HIGH

0 0.9 μs

HD:DAT

100 ns

SU:DAT

0.6 μs

SU:STA

0.6 μs

SU:STO

(Note 6) 400 pF

C

B

0.1C

0.1C

20 +

20 +

B

B

300 ns

300 ns