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REV: 010906
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:
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.
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.
APPLICATIONS
Digital Video Cameras
Commercial Two-Way Radios
Industrial PDAs and Handheld PC Data Terminals
Portable GPS Navigation Systems
TYPICAL OPERATING CIRCUIT
FEATURES
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
Interface
Tiny 8-Pin TSSOP Package Embeds Easily in
Battery Packs Using Thin Prismatic Cells
PIN CONFIGURATION
DQ
SNS
VDD
VSS
P+
P-
DQ
Protection
Circuit
DS2781
PIO
VB
VIN
OVD
ORDERING INFORMATION
PART MARKING PACKAGE
DS2781E+ 2781
TSSOP
DS2781E+T&R 2781
Tape-and-Reel
+ Denotes lead-free package.
1-Wire is a registered trademark of Dallas Semiconductor.
TOP VIEW
1
2
3
4
5
6
7
8
VB
VSS
VIN
VPLS
PIO
SNS
OVD
DQ
TSSOP-8
DS2781
1-Cell or 2-Cell
Standalone Fuel Gauge IC
DS2781: Two-Cell Standalone Fuel Gauge IC
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ABSOLUTE MAXIMUM RATINGS
Voltage on VPLS, VIN Relative to VSS
-0.3V to +12V
Voltage Range on Any Pin Relative to VSS
-0.3V to +6.0V
Continuous Sink Current, DQ, PIO
20mA
Operating Temperature Range
-40C to +85C
Storage Temperature Range
-55C to +125C
Soldering Temperature (10s)
+260C
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
= -20C to +70C, unless otherwise noted. Typical values are at T
A
= +25C)
PARAMETER SYMBOL
CONDITIONS
MIN
TYP
MAX
UNITS
Supply Voltage
V
PLS
(Note
1)
+2.5
+10
V
VIN Voltage Range
(Note 1)
-0.3
V
PLS
+ 0.3
V
DQ, PIO Voltage Range
(Note 1)
-0.3
+5.5
V
VB Output Voltage
V
VB
V
PLS
> 3.0V,
I
VB
= 500A,
(Note 1)
2.5 2.8 3.1 V
OVD Voltage Range
(Note 1)
-0.3
V
VB
+ 0.3
V
DC ELECTRICAL CHARACTERISTICS
(V
PLS
= 2.5V to 10V, T
A
= -20C to +70C, unless otherwise noted. Typical values are at T
A
= +25C.)
PARAMETER SYMBOL
CONDITIONS
MIN
TYP
MAX
UNITS
ACTIVE Current
I
ACTIVE
I
VB
= 0
70
95
A
T
A
> +50C, I
VB
= 0
10
SLEEP Mode Current
I
SLEEP
I
VB
= 0, (Note 5)
3
5
A
Input Logic High: DQ, PIO
V
IH
(Note
1)
1.5
V
Input Logic Low: DQ, PIO
V
IL
(Note
1)
0.6
V
Output Logic Low: DQ, PIO
V
OL
I
OL
= 4mA (Note 1)
0.4
V
Pulldown Current: DQ, PIO
I
PD
V
DQ
, V
PIO
= 0.4V
0.2
A
Input Logic High: OVD
V
IH
(Note 1)
0.7 x V
VB
V
Input Logic Low: OVD
V
IL
(Note 1)
0.3 x V
VB
V
VIN Input Resistance
R
IN
15
M
W
DQ Capacitance
C
DQ
(Note
4)
50
pF
DQ SLEEP Timeout
t
SLEEP
DQ
<
V
IL
1.5
2
2.5
s
UVTH = 1, (Note 1)
4.8
4.9
5.0
Undervoltage SLEEP
Threshold
V
SLEEP
UVTH = 0, (Note 1)
2.40
2.45
2.50
V
ELECTRICAL CHARACTERISTICS: TEMPERATURE, VOLTAGE, CURRENT
(V
PLS
= 2.5V to 10V, T
A
= -20C to +70C, unless otherwise noted. Typical values are at T
A
= +25C.)
PARAMETER SYMBOL
CONDITIONS
MIN
TYP
MAX
UNITS
Temperature Resolution
T
LSB
0.125
C
Temperature Error
T
ERR
3 C
Voltage Resolution
V
LSB
9.76
mV
DS2781: Two-Cell Standalone Fuel Gauge IC
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PARAMETER SYMBOL
CONDITIONS
MIN
TYP
MAX
UNITS
Voltage Full-Scale
V
FS
0
9.9902 V
Voltage Error
V
ERR
100 mV
Current Resolution
I
LSB
1.56
V
Current Full-Scale
I
FS
51.2 mV
Current Gain Error
I
GERR
(Note
2)
1
% Full-
Scale
Current Offset Error
I
OERR
0C T
A
+70C,
(Note 4)
- 7.82
+ 12.5
V
Accumulated Current Offset
q
OERR
0C T
A
+70C,
VSNS = VSS (Notes 3, 4)
- 188
+ 0
Vhr/
day
T
A
= +25C, V
PLS
= 7.6V
1
Timebase Error
t
ERR
2
%
ELECTRICAL CHARACTERISTICS: 1-WIRE INTERFACE, STANDARD
(V
PLS
= 2.5V to 10V, T
A
= -20C to +70C.)
PARAMETER SYMBOL
CONDITIONS
MIN
TYP
MAX
UNITS
Time Slot
t
SLOT
60
120
ms
Recovery Time
t
REC
1
ms
Write-0 Low Time
t
LOW0
60
120
ms
Write-1 Low Time
t
LOW1
1
15
ms
Read Data Valid
t
RDV
15
ms
Reset Time High
t
RSTH
480
ms
Reset Time Low
t
RSTL
480
960
ms
Presence Detect High
t
PDH
15
60
ms
Presence Detect Low
t
PDL
60
240
ms
ELECTRICAL CHARACTERISTICS: 1-WIRE INTERFACE, OVERDRIVE
(V
PLS
= 2.5V to 10V, T
A
= -20C to +70C.)
PARAMETER SYMBOL
CONDITIONS
MIN
TYP
MAX
UNITS
Time Slot
t
SLOT
6
16
ms
Recovery Time
t
REC
1
ms
Write-0 Low Time
t
LOW0
6
16
ms
Write-1 Low Time
t
LOW1
1
2
ms
Read Data Valid
t
RDV
2
ms
Reset-Time High
t
RSTH
48
ms
Reset-Time Low
t
RSTL
48
80
ms
Presence-Detect High
t
PDH
2
6
ms
Presence-Detect Low
t
PDL
8
24
ms
DS2781: Two-Cell Standalone Fuel Gauge IC
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EEPROM RELIABILITY SPECIFICATION
(V
PLS
= 2.5V to 10V, T
A
= -20C to +70C, unless otherwise noted. Typical values are at T
A
= +25C.)
PARAMETER SYMBOL
CONDITIONS
MIN
TYP
MAX
UNITS
EEPROM Copy Time
t
EEC
15 ms
EEPROM Copy Endurance
N
EEC
T
A
= +50C
50,000
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 VB
Internal Supply. Bypass to VSS with a 0.1F capacitor.
2 VSS
Device Ground. Connect directly to the negative terminal of the cell stack. Connect the
sense resistor between VSS and SNS.
3 VIN
Voltage Sense Input. The voltage of the battery pack is monitored through this input pin
with respect to the VSS pin.
4 VPLS
Power-Supply Input. Connect to the positive terminal of the battery pack through a
decoupling network.
5 DQ
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.
6 OVD
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.
7 SNS
Sense Resistor Connection. Connect to the negative terminal of the battery pack.
Connect the sense resistor between VSS and SNS.
8 PIO
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
).
DS2781: Two-Cell Standalone Fuel Gauge IC
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Figure 1. Block Diagram
V
POR
DQ
1-Wire
Interface
BIAS/VREF
Timebase
Temp
&
Voltage
ADC
Current ADC
15 bit + sign
Rate,
Temperature
Compensation
EEPROM
Status
&
Control
Accumulated
Current
EN
SNS
VSS
VPLS
OVD
PIO
VIN
Voltage
Regulator
VB
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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