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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 I

C interface, the DS2741 gives the host

system access to current measurement and accumula-

tion registers. The 7-bit slave address is factory pro-

grammable, 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

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

DS2741

TDFN

TOP VIEW

EP*

*EXPOSED PAD

245

13 11 10

RS- RS- SLP

RS+ RS+ SDA

RS-

RS+

RS-

RS+

GND

SCL

DNC

Pin Configuration

Ordering Information

DS2741

2.2kΩ

1.8V

2.2kΩ

0.1μF

RS+

GND

SLP

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*

Summary of content (9 pages)

PAGE 1
Rev 0; 8/08 Current Monitor and Accumulator with Integrated Sense Resistor 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.
PAGE 2
DS2741 Current Monitor and Accumulator with Integrated Sense Resistor ABSOLUTE MAXIMUM RATINGS 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. Voltage Range on VCC Relative to GND ...............-0.5V to +6.
PAGE 3
Current Monitor and Accumulator with Integrated Sense Resistor DS2741 TEMPERATURE SENSOR CHARACTERISTICS (VCC = +2.5V to +4.5V, TA = -20°C to +70°C, unless otherwise noted.) PARAMETER SYMBOL CONDITIONS MIN TYP Temperature Error MAX UNITS ±5 °C MAX UNITS 400 kHz AC ELECTRICAL CHARACTERISTICS: I2C INTERFACE (2.5V ≤ VCC ≤ 4.5V, TA = -20°C to +70°C, timing referenced to VIL(MAX) and VIH(MIN). See Figure 4.
PAGE 4
Typical Operating Characteristics (VCC = +2.5V to +4.5V, TA = -20°C to +70°C, unless otherwise noted.) 40 30 20 1.5 SDA = SCL = VCC SLP = GND TA = +25°C SLP = SDA = SCL = VCC = +3.5V 60 SUPPLY CURRENT (μA) SLEEP-MODE CURRENT (μA) 1.0 0.5 50 40 30 20 10 10 0 0 3.0 3.5 4.0 3.0 3.5 4.5 4.0 -20 -10 0 10 20 30 40 50 60 SUPPLY VOLTAGE (V) SUPPLY VOLTAGE (V) TEMPERATURE (°C) SUPPLY CURRENT vs.
PAGE 5
Current Monitor and Accumulator with Integrated Sense Resistor PIN NAME FUNCTION 1–4 RS+ Sense Resistor High Side. Connection to high side of internal 38m sense resistor. All RS+ pins must be connected together. 5 SDA Serial Data Input/Output. SDA is the input/output pin for the I2C serial interface. The SDA pin is an open-drain output and requires an external pullup resistor. 6 SCL Serial Clock Input. SCL is used to synchronize data movement on the I2C serial interface. 7 VCC Supply Voltage.
PAGE 6
DS2741 Current Monitor and Accumulator with Integrated Sense Resistor Detailed Description The DS2741 is a small, low-cost, current-sensing and accumulation IC that is intended for current-monitoring applications. The differential voltage measured across the on-chip 38mΩ sense resistor is digitized by an internal ADC that provides an accurately scaled digital signed 10-bit value that represents bidirectional current up to ±2.5A.
PAGE 7
Current Monitor and Accumulator with Integrated Sense Resistor Table 1. Register Map ADDRESS (HEX) 00h to 0Fh DESCRIPTION READ/WRITE Reserved — 10h and 11h Current Accumulator Register 12h and 13h Reserved R/W — 14h Temperature Register R 15h Reserved — 16h and 17h Current Register 18h to FFh R Reserved — I2C Bus Interface I2C Definitions The following terminology is commonly used to describe I2C data transfers. Master Device: The master device controls the slave devices on the bus.
PAGE 8
Current Monitor and Accumulator with Integrated Sense Resistor DS2741 Bit Read: At the end a write operation, the master must release the SDA bus line for the proper amount of setup time (Figure 4) before the next rising edge of SCL during a bit read. The device shifts out each bit of data on SDA at the falling edge of the previous SCL pulse, and the data bit is valid at the rising edge of the current SCL pulse.
PAGE 9
Current Monitor and Accumulator with Integrated Sense Resistor DS2741 COMMUNICATIONS KEY NOTES S START A ACK P STOP N NACK SR REPEATED START WHITE BOXES INDICATE THE MASTER IS CONTROLLING SDA SHADED BOXES INDICATE THE SLAVE IS CONTROLLING SDA X X X X X X X X 1) ALL BYTES ARE SENT MOST SIGNIFICANT BIT FIRST. 2) THE FIRST BYTE SENT AFTER A START CONDITION IS ALWAYS THE SLAVE ADDRESS FOLLOWED BY THE READ/WRITE BIT.