DS2781
1-Cell or 2-Cell
Standalone Fuel Gauge IC
GENERAL DESCRIPTION
The DS2781 measures voltage, temperature, and
current, and estimates available capacity for
rechargeable Lithium-Ion and Lithium-Ion Polymer
batteries. Cell stack characteristics and application
parameters used in the calculations are stored in on-
chip EEPROM. The available capacity registers
report a conservative estimate of the amount of
charge that can be removed given the current
temperature, discharge rate, stored charge and
application parameters. Capacity estimation is
reported in milliamp hours remaining and percentage
of full.
FEATURES
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Precision Voltage, Temperature, and Current
Measurement System
Operates in One-Cell or Two--Cell Applications
Accurate, Temperature Stable Internal Time
Base
Absolute and Relative Capacity Estimated from
Coulomb Count, Discharge Rate, Temperature,
and Battery Cell Characteristics
Accurate Warning of Low Battery Conditions
Automatic Backup of Coulomb Count and Age
Estimation to Nonvolatile (NV) EEPROM
Gain and Tempco Calibration Allows the Use of
Low-Cost Sense Resistors
24-Byte Battery/Application Parameter EEPROM
16-Byte User EEPROM
Unique ID and Multidrop 1-Wire
Ò
Interface
Tiny 8-Pin TSSOP Package Embeds Easily in
Battery Packs Using Thin Prismatic Cells
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APPLICATIONS
Digital Video Cameras
Commercial Two-Way Radios
Industrial PDAs and Handheld PC Data Terminals
Portable GPS Navigation Systems
TYPICAL OPERATING CIRCUIT
P+
PIN CONFIGURATION
TOP VIEW
TSSOP-8
DS2781
DQ
DQ
PIO
OVD
SNS
VDD
VIN
VB
VSS
VB
VSS
VIN
VPLS
Protection
Circuit
1
2
3
4
8
7
6
5
PIO
SNS
OVD
DQ
P-
ORDERING INFORMATION
PART
DS2781E+
DS2781E+T&R
MARKING
2781
2781
PACKAGE
TSSOP
Tape-and-Reel
+ Denotes lead-free package.
1-Wire is a registered trademark of Dallas Semiconductor.
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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REV: 010906
DS2781: Two-Cell Standalone Fuel Gauge IC
ABSOLUTE MAXIMUM RATINGS
Voltage on VPLS, VIN Relative to VSS
Voltage Range on Any Pin Relative to VSS
Continuous Sink Current, DQ, PIO
Operating Temperature Range
Storage Temperature Range
Soldering Temperature (10s)
-0.3V to +12V
-0.3V to +6.0V
20mA
-40°C to +85°C
-55°C to +125°C
+260°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 the absolute maximum rating conditions for extended periods may affect device.
RECOMMENDED DC OPERATING CHARACTERISTICS
(V
PLS
= 2.5V to 10V, T
A
= -20°C to +70°C, unless otherwise noted. Typical values are at T
A
= +25°C)
PARAMETER
Supply Voltage
VIN Voltage Range
DQ, PIO Voltage Range
VB Output Voltage
OVD Voltage Range
V
VB
SYMBOL
V
PLS
CONDITIONS
(Note 1)
(Note 1)
(Note 1)
V
PLS
> 3.0V,
I
VB
= 500µA,
(Note 1)
(Note 1)
MIN
+2.5
-0.3
-0.3
2.5
-0.3
2.8
TYP
MAX
+10
V
PLS
+ 0.3
+5.5
3.1
V
VB
+ 0.3
UNITS
V
V
V
V
V
DC ELECTRICAL CHARACTERISTICS
(V
PLS
= 2.5V to 10V, T
A
= -20°C to +70°C, unless otherwise noted. Typical values are at T
A
= +25°C.)
PARAMETER
ACTIVE Current
SLEEP Mode Current
Input Logic High: DQ, PIO
Input Logic Low: DQ, PIO
Output Logic Low: DQ, PIO
Pulldown Current: DQ, PIO
Input Logic High: OVD
Input Logic Low: OVD
VIN Input Resistance
DQ Capacitance
DQ SLEEP Timeout
Undervoltage SLEEP
Threshold
SYMBOL
I
ACTIVE
I
SLEEP
V
IH
V
IL
V
OL
I
PD
V
IH
V
IL
R
IN
C
DQ
t
SLEEP
V
SLEEP
CONDITIONS
I
VB
= 0
T
A
> +50°C, I
VB
= 0
I
VB
= 0, (Note 5)
(Note 1)
(Note 1)
I
OL
= 4mA (Note 1)
V
DQ
, V
PIO
= 0.4V
(Note 1)
(Note 1)
(Note 4)
DQ < V
IL
UVTH = 1, (Note 1)
UVTH = 0, (Note 1)
1.5
0.6
0.4
0.2
0.7 x V
VB
0.3 x V
VB
15
1.5
4.8
2.40
50
2
4.9
2.45
2.5
5.0
2.50
3
MIN
TYP
70
MAX
95
10
5
UNITS
µA
µA
V
V
V
µA
V
V
MW
pF
s
V
ELECTRICAL CHARACTERISTICS: TEMPERATURE, VOLTAGE, CURRENT
(V
PLS
= 2.5V to 10V, T
A
= -20°C to +70°C, unless otherwise noted. Typical values are at T
A
= +25°C.)
PARAMETER
Temperature Resolution
Temperature Error
Voltage Resolution
SYMBOL
T
LSB
T
ERR
V
LSB
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9.76
CONDITIONS
MIN
TYP
0.125
±3
MAX
UNITS
°C
°C
mV
DS2781: Two-Cell Standalone Fuel Gauge IC
PARAMETER
Voltage Full-Scale
Voltage Error
Current Resolution
Current Full-Scale
Current Gain Error
Current Offset Error
Accumulated Current Offset
Timebase Error
SYMBOL
V
FS
V
ERR
I
LSB
I
FS
I
GERR
I
OERR
q
OERR
t
ERR
(Note 2)
0°C
≤
T
A
≤
+70°C,
(Note 4)
0°C
≤
T
A
≤
+70°C,
VSNS = VSS (Notes 3, 4)
T
A
= +25°C, V
PLS
= 7.6V
- 7.82
- 188
1.56
±51.2
±1
+ 12.5
+0
±1
±2
CONDITIONS
MIN
0
TYP
MAX
9.9902
±100
UNITS
V
mV
µV
mV
% Full-
Scale
µV
µVhr/
day
%
ELECTRICAL CHARACTERISTICS: 1-WIRE INTERFACE, STANDARD
(V
PLS
= 2.5V to 10V, T
A
= -20°C to +70°C.)
PARAMETER
Time Slot
Recovery Time
Write-0 Low Time
Write-1 Low Time
Read Data Valid
Reset Time High
Reset Time Low
Presence Detect High
Presence Detect Low
SYMBOL
t
SLOT
t
REC
t
LOW0
t
LOW1
t
RDV
t
RSTH
t
RSTL
t
PDH
t
PDL
480
480
15
60
960
60
240
CONDITIONS
MIN
60
1
60
1
120
15
15
TYP
MAX
120
UNITS
ms
ms
ms
ms
ms
ms
ms
ms
ms
ELECTRICAL CHARACTERISTICS: 1-WIRE INTERFACE, OVERDRIVE
(V
PLS
= 2.5V to 10V, T
A
= -20°C to +70°C.)
PARAMETER
Time Slot
Recovery Time
Write-0 Low Time
Write-1 Low Time
Read Data Valid
Reset-Time High
Reset-Time Low
Presence-Detect High
Presence-Detect Low
SYMBOL
t
SLOT
t
REC
t
LOW0
t
LOW1
t
RDV
t
RSTH
t
RSTL
t
PDH
t
PDL
48
48
2
8
80
6
24
CONDITIONS
MIN
6
1
6
1
16
2
2
TYP
MAX
16
UNITS
ms
ms
ms
ms
ms
ms
ms
ms
ms
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DS2781: Two-Cell Standalone Fuel Gauge IC
EEPROM RELIABILITY SPECIFICATION
(V
PLS
= 2.5V to 10V, T
A
= -20°C to +70°C, unless otherwise noted. Typical values are at T
A
= +25°C.)
PARAMETER
EEPROM Copy Time
EEPROM Copy Endurance
SYMBOL
t
EEC
N
EEC
T
A
= +50°C
50,000
CONDITIONS
MIN
TYP
MAX
15
UNITS
ms
cycles
Note 1:
All voltages are referenced to VSS.
Note 2:
Factory calibrated accuracy. Higher accuracy can be achieved by in-system calibration by the user.
Note 3:
Accumulation Bias register set to 00h. Current Offset Bias register set to 00h. NBEN bit = 0.
Note 4:
Parameters guaranteed by design.
Note 5:
Internal voltage regulator active.
PIN DESCRIPTION
PIN
NAME
FUNCTION
1
2
3
4
5
VB
VSS
VIN
VPLS
DQ
Internal Supply.
Bypass to VSS with a 0.1µF capacitor.
Device Ground.
Connect directly to the negative terminal of the cell stack. Connect the
sense resistor between VSS and SNS.
Voltage Sense Input.
The voltage of the battery pack is monitored through this input pin
with respect to the VSS pin.
Power-Supply Input.
Connect to the positive terminal of the battery pack through a
decoupling network.
Data Input/Output.
1-Wire data line. Open-drain output driver. Connect this pin to the
DATA terminal of the battery pack. This pin has a weak internal pulldown (I
PD
) for sensing
pack disconnection from host or charger.
1-Wire Bus Speed Control.
Input logic level selects the speed of the 1-Wire bus. Logic 1
selects overdrive (OVD) and Logic 0 selects standard timing (STD). On a multidrop bus,
all devices must operate at the same speed.
Sense Resistor Connection.
Connect to the negative terminal of the battery pack.
Connect the sense resistor between VSS and SNS.
Programmable I/O Pin.
Can be configured as input or output to monitor or control user-
defined external circuitry. Output driver is open drain. This pin has an weak internal
pulldown (I
PD
).
6
7
8
OVD
SNS
PIO
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DS2781: Two-Cell Standalone Fuel Gauge IC
Figure 1. Block Diagram
VPLS
VB
Voltage
Regulator
V
POR
EN
PIO
VIN
DQ
OVD
BIAS/VREF
Timebase
1-Wire
Interface
Status
&
Control
Temp
&
Voltage
ADC
EEPROM
Accumulated
Current
Current ADC
15 bit + sign
Rate,
Temperature
Compensation
VSS
SNS
DETAILED DESCRIPTION
The DS2781 operates directly from 2.5V to 10V and supports single or dual cell Lithium-ion battery packs.
Nonvolatile storage is provided for cell compensation and application parameters. Host side development of fuel-
gauging algorithms is eliminated. On-chip algorithms and convenient status reporting of operating conditions
reduce the serial polling required of the host processor.
Additionally, 16 bytes of EEPROM memory are made available for the exclusive use of the host system and/or
pack manufacturer. The additional EEPROM memory can be used to facilitate battery lot and date tracking and
non-volatile storage of system or battery usage statistics.
A Dallas 1-Wire interface provides serial communication at the standard 16kbps or overdrive 140kbps speeds
allows access to data registers, control registers and user memory. A unique, factory programmed 64-bit
registration number (8-bit family code + 48-bit serial number + 8-bit CRC) assures that no two parts are alike and
enables absolute traceability. The Dallas 1-Wire interface on the DS2781 supports multidrop capability so that
multiple slave devices may be addressed with a single pin.
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