19-4632; 5/09
DS2746
Low-Cost 2-Wire Battery Monitor
with Ratiometric A/D Inputs
www.maxim-ic.com
GENERAL DESCRIPTION
The DS2746 provides system-side battery capacity
monitoring in cost-sensitive applications. Voltage,
bidirectional current, and accumulated current
measurement data is provided to the host processor
over a 2-wire interface. Offset bias and offset
blanking features greatly enhance the accuracy of
the coulomb counter. In addition, the DS2746 has
two auxiliary A/D inputs to sample the pack
identification resistor, thermistor, or other voltage
source. The results are reported as a ratiometric
fraction of the supply voltage eliminating error related
to the supply. The DS2746 reduces the total power
consumption of the measurement circuit by enabling
the resistor dividers, through the V
OUT
pin, only while
measurements are made. When the system is
inactive, a low power sleep mode reduces current
consumption while maintaining the coulomb count.
The tiny 3mm × 3mm TDFN package consumes only
9mm
2
of PCB space.
FEATURES
14-Bit Bidirectional Current Measurement
-
6.25V LSB, ±51.2mV Dynamic Range
-
416.7A LSB, ±3.4A Range (R
SNS
= 15m)
Current Accumulation Register Resolution
-
6.25Vhr LSB, 409.6mVh Range
-
417Ahr LSB, 27.31Ah Range
11-Bit Battery Voltage Measurement
-
2.44mV LSB, 0V to 4.5V Input Range
-
±10mV Accuracy at 3.6V Input
Two 11-Bit Aux Input Voltage Measurements
-
Ratiometric Inputs Eliminate Supply Error
-
VOUT drives Dividers, Reduces Power
-
±8 LSB Accuracy
Low Power Consumption:
-
Active Current: 70A typical, 100A max
-
Sleep Current: 1A typical, 3A max
ORDERING INFORMATION
APPLICATIONS
2.5G/3G Wireless Handsets
PDA/Smartphones
Digital Still and Video Cameras
Handheld Computers and Terminals
PART
DS2746G+
DS2746G+T&R
TEMP RANGE
-20ºC to +70ºC
-20ºC to +70ºC
PIN-PACKAGE
10-Pin 3
mm×
3mm
TDFN
DS2746G+ in Tape-
and-Reel
+ Denotes lead(Pb)-free/RoHS-compliant package.
PIN CONFIGURATION
TYPICAL OPERATING CIRCUIT
TOP VIEW
3mm
×
3mm TDFN
Note:
Some revisions of this device may incorporate deviations from published specifications known as errata. Multiple revisions of any device
may be simultaneously available through various sales channels. For information about device errata, click here:
www.maxim-ic.com/errata.
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DS2746 Low-Cost 2-Wire Battery Monitor
ABSOLUTE MAXIMUM RATINGS
Voltage Range on Any Pin Relative to Ground
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
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 the absolute maximum rating conditions for extended periods may affect device reliability.
RECOMMENDED DC OPERATING CONDITIONS
(V
DD
= 2.5V to 4.5V, T
A
= -20°C to +70°C.)
PARAMETER
Supply Voltage
Data I/O Pins
Programmable I/O Pin
V
IN
, AIN0, AIN1 Pin
SYMBOL
V
DD
SCL, SDA
PIO
V
IN
, AIN0,
AIN1
CONDITIONS
(Note 1)
(Note 1)
(Note 1)
(Note 1)
MIN
+2.5
-0.3
-0.3
-0.3
TYP
MAX
+4.5
+5.5
+5.5
V
DD
+ 0.3
UNITS
V
V
V
V
DC ELECTRICAL CHARACTERISTICS
(V
DD
= 2.5V to 4.5V, T
A
= -20°C to +70°C.)
PARAMETER
Active Current
Sleep-Mode Current
Current Resolution
Current Full-Scale Magnitude
Current Offset
Current Gain Error
Timebase Accuracy
SYMBOL
I
ACTIVE
I
SLEEP
I
LSB
I
FS
I
OERR
I
GERR
t
ERR
(Note 1)
(Note 2)
(Note 11)
V
DD
= 3.6V at +25°C
T
A
= 0C to +70C
T
A
= -20C to +70C
V
DD
= V
IN
= 3.6V
-12.5
-1.5
-1
-2
-3
-10
-20
15
(Note 10)
I
O
= 1mA
V
ODIS
bit = 0
(Note 1)
(Note 1)
I
OL
= 4mA, (Note 1)
V
DD
= 4.2V,
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0.2
-8
V
DD
-0.1
13.3
1.5
0.6
0.4
+8
14.2
CONDITIONS
V
DD
= 4.5V
V
DD
= 2.0V,
SCL, SDA = Vss
SCL, SDA = Vss
MIN
TYP
70
0.5
1
6.25
±51.2
+12.5
+1.5
+1
+2
+3
+10
+20
MAX
100
105
1.0
3
V
mV
V
% of
reading
%
UNITS
A
A
Voltage Error
Input Resistance
V
IN
, AIN0, AIN1
AIN0, AIN1 Error
V
OUT
Output Drive
V
OUT
Precharge Time
Input Logic High:
SCL, SDA
Input Logic Low:
SCL, SDA
Output Logic Low:
SDA
Pulldown Current:
V
GERR
R
IN
AIN
GERR
t
PRE
V
IH
V
IL
V
OL
I
PD
mV
MΩ
LSB
V
ms
V
V
V
A
DS2746 Low-Cost 2-Wire Battery Monitor
SCL, SDA
Input Capacitance:
SCL, SDA
Bus Low Timeout
V
PIN
= 0.4V
C
BUS
t
SLEEP
(Note 3)
1.5
50
2.2
pF
S
DC ELECTRICAL CHARACTERISTICS: 2-WIRE INTERFACE
(V
DD
= 2.5V to 4.5V, T
A
= -20°C to +70°C.)
PARAMETER
SCL Clock Frequency
Bus Free Time Between a
STOP and START Condition
Hold Time (Repeated)
START Condition
Low Period of SCL Clock
High Period of SCL Clock
Setup Time for a Repeated
START Condition
Data Hold Time
Data Setup Time
Rise Time of Both SDA and
SCL Signals
Fall Time of Both SDA and
SCL Signals
Setup Time for STOP
Condition
Spike Pulse Widths
Suppressed by Input Filter
Capacitive Load for Each Bus
Line
SCL, SDA Input Capacitance
Note 1:
Note 2:
Note 3:
Note 4:
Note 5:
Note 6:
Note 7:
Note 8:
Note 9:
Note 10:
Note 11:
SYMBOL
f
SCL
t
BUF
t
HD:STA
t
LOW
t
HIGH
t
SU:STA
t
HD:DAT
t
SU:DAT
t
R
t
F
t
SU:STO
t
SP
C
B
C
BIN
CONDITIONS
(Note 4)
MIN
0
1.3
TYP
MAX
400
UNITS
KHz
µs
µs
µs
µs
µs
(Note 5)
0.6
1.3
0.6
0.6
(Note 6, 7)
(Note 6)
0
100
20 + 0.1C
B
20 + 0.1C
B
0.6
0.9
µs
ns
300
300
ns
ns
µs
(Note 8)
(Note 9)
0
50
400
60
ns
pF
pF
All voltages are referenced to V
SS
.
Offset specified after auto-calibration cycle and Current Offset Bias register = 0x00.
The DS2746 enters the sleep mode 1.5s to 2.2s after ( SCL < V
il
.) AND ( SDA < V
il
).
Timing must be fast enough to prevent the DS2746 from entering sleep mode due to bus low for period > t
SLEEP
.
f
SCL
must meet the minimum clock low time plus the rise/fall times.
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.
This device internally provides a hold time of at least 100ns for the SDA signal (referred to the VIHmin of the SCL signal) to
bridge the undefined region of the falling edge of SCL.
Filters on SDA and SCL suppress noise spikes at the input buffers and delay the sampling instant.
C
b
– total capacitance of one bus line in pF.
The AIN
GERR
spec is only valid when this equation is satisfied: (V
AINx
+ 2V
OUT
)
(11.6V - (T
A
- 25C)10mV/C). See Figure 1.
Accuracy specification valid for V
SS
- SNS
≥
±2.5mV, below which offset error is dominant.
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DS2746 Low-Cost 2-Wire Battery Monitor
Figure 1. Valid Range for AIN
GERR
Accuracy Specification
100%
AINx PIN VOLTAGE AS A PERCENTAGE
OF VOUT (%)
°C
70
°C
25
AINx Voltage
Measurement Error
Not Specified
C
0
°
-2
67%
57%
48%
AINx Voltage Measurement Error
≤
AIN
GERR
Specification
0%
2.5V
3.7
3.86
4.0
VOUT PIN VOLTAGE (V)
4.5V
Figure 2. 2-Wire Bus Timing Diagram
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DS2746 Low-Cost 2-Wire Battery Monitor
PIN DESCRIPTION
PIN
1
2
3
4
5
6
7
8
9
10
PAD
NAME
AIN1
AIN0
SCL
SDA
SNS
V
SS
CTG
V
OUT
V
IN
V
DD
PAD
FUNCTION
Aux Voltage Input Number 1.
Aux Voltage Input Number 0.
Serial Clock Input.
Input only 2-wire clock line. Connect this pin to the CLOCK signal of
the 2-wire interface. This pin has a 0.2µA typical pulldown to sense disconnection.
Serial Data Input / Output.
Open drain 2-wire data line. Connect this pin to the DATA
signal of the 2-wire interface. This pin has a 0.2µA typical pulldown to sense
disconnection.
Current-Sense Input.
Connect to the handset side of the sense resistor.
Device Ground.
Connect to the battery side of the sense resistor.
Connect to Ground.
Connect to the battery side of the sense resistor.
Voltage Out.
Supply for Aux input voltage Measurement dividers. Connect to high side of
resistor divider circuits.
Battery Voltage Input.
The voltage of the cell pack is measured through this pin.
Power-Supply Input.
2.5V to 4.5V input range. Connect to system power through a
decoupling network.
Exposed Pad.
Connect to V
SS.
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