DS2755
High-Accuracy Battery
Fuel Gauge with Snapshot
www.maxim-ic.com
FEATURES
Snapshot Mode Allows Instantaneous Power
Measurement
Accurate Current Measurement for Coulomb
Counting (Current Accumulation)
- 2% ±4μV over ±64mV Input Range
- 2% ±200μA over ±3.2A Range Using a 20mΩ
Sense Resistor
Current Measurement
- 9-Bit Bidirectional Snapshot Measurement
- 12-Bit Bidirectional Average Updated Every
88ms
- 15-Bit Bidirectional Average Updated Every 2.8s
Voltage Measurement
- 9-Bit Snapshot Measurement
- 10-Bit Measurement Updated Every 4ms
Temperature Measurement
- 10-Bit Measurement, 0.125°C Resolution Using
Integrated Sensor
Host Alerted When Accumulated Current or
Temperature Exceeds User-Selectable Limits
96 Bytes of Lockable EEPROM
8 Bytes of General-Purpose SRAM
Dallas 1-Wire
®
Interface with Unique 64-Bit
Device Address with Standard 16kbps or
Overdrive 142kbps Timing
3mm Dimension of 8-Pin TSSOP Package Allows
Mounting on Side of Thin Prismatic Li+ and
Li+/Polymer Cells
PIN CONFIGURATION
V
IN
V
SS
PIO
V
DD
1
2
2
3
2
4
8
7
6
5
DQ
SNS
IS2
IS1
DS2755E
8-Pin TSSOP Package
DESCRIPTION
The DS2755 high-precision battery fuel gauge is a
data-acquisition and information-storage device
tailored for cost-sensitive and space-constrained 1-
cell Li+/polymer battery-pack applications. The
DS2755 provides the key hardware components
required to accurately estimate remaining capacity by
integrating low-power, precision measurements of
temperature,
voltage,
current,
and
current
accumulation, as well as nonvolatile (NV) data
storage, into the small footprint of a 3.0mm x 4.4mm
8-pin TSSOP package.
Through its 1-Wire interface, the DS2755 gives the
host system read/write access to status and control
registers, instrumentation registers, and general-
purpose data storage. Each device has a unique
factory-programmed 64-bit net address that allows it
to be individually addressed by the host system,
supporting multibattery operation.
APPLICATIONS
Cell Phones
Digital Cameras
Smartphones
PDAs
Portable Consumer Products
ORDERING INFORMATION
PART
DS2755E+
DS2755E+T&R
MARKING
2755
2755
TEMP RANGE
-20°C to +70°C
-20°C to +70°C
DESCRIPTION
8-Pin TSSOP, Lead Free
DS2755E+ on Tape-and-Reel
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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020507
DS2755: High-Accuracy Battery Fuel Gauge with Snapshot
DESCRIPTION (CONTINUED)
The DS2755 performs temperature, voltage, and current measurement to a resolution sufficient to support process-
monitoring applications such as battery charge control and remaining capacity estimation. Temperature is
measured using an on-chip sensor, eliminating the need for a separate thermistor. Bidirectional current
measurement supporting current accumulation (coulomb counting) is accomplished using an external current
sense resistor.
The host system can configure the DS2755 to signal critical conditions to reduce polling overhead. The interrupt
fires when programmable upper and lower thresholds of temperature or coulomb count are crossed. The user can
select either the DQ pin or PIO pin as the interrupt signal.
The programmable I/O pin allows the host system to sense and control other electronics in the pack, including
switches, vibration motors, speakers, and LEDs, or the I/O pin can be configured as an interrupt output.
Three types of memory are provided on the DS2755 for battery information storage: EEPROM, lockable EEPROM,
and SRAM. EEPROM memory saves important battery data in true NV memory that is unaffected by severe battery
depletion, accidental shorts, or ESD events. Lockable EEPROM becomes ROM when locked to provide additional
security for unchanging battery data. SRAM provides inexpensive storage for temporary data.
Figure 1.
APPLICATION EXAMPLE
PACK+
500
1k
150
150
PIO
DATA
1 Cell Li+
5.6V
(1)
VIN
VSS
PIO
VDD
103
DQ
SNS
IS2
IS1
5.6V
(1)
5.6V
(1)
102
104
Protection IC
(Li+/Polymer)
DS2755
R
SNS
2.5V
(1)
PACK -
(1) Optional component(s) for robust ESD performance
SNS
10kΩ
10kΩ
V
SS
R
KS
IS1
ADC
Input
DS2755
R
KS
IS2
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DS2755: High-Accuracy Battery Fuel Gauge with Snapshot
ABSOLUTE MAXIMUM RATINGS*
Voltage on PIO Pin, Relative to V
SS
Voltage on All Other Pins, Relative to V
SS
Continuous Sink Current, DQ, PIO
Operating Temperature Range
Storage Temperature Range
Soldering Temperature
-0.3V to +12V
-0.3V to +6V
12mA
-40°C to +85°C
-55°C to +125°C
See J-STD-020 Specification
*
This is a stress rating only and functional operation of the device at these or any other conditions above those indicated in the operation
sections of this specification is not implied. Exposure to absolute maximum rating conditions for extended periods of time may affect reliability.
RECOMMENDED DC OPERATING CONDITIONS
PARAMETER
Supply Voltage
Data Pin
V
IN
Pin
SYMBOL
V
DD
DQ
V
IN
CONDITIONS
(Note 1)
(Note 1)
(Note 1)
(2.5V
≤
V
DD
≤
5.5V, T
A
= -20°C to +70°C.)
MIN
TYP
MAX
UNITS
2.5
5.5
V
-0.3
+5.5
V
-0.3
+5.5
V
DC ELECTRICAL CHARACTERISTICS
PARAMETER
Active Current
Sleep-Mode Current
Current Measurement
Input Range
Current Register Offset
Error
Current Gain Error
24 Hour Accumulated
Current Error
Current Sampling
Frequency
IS1-VSS, IS2-SNS Filter
Resistors
Input Resistance: V
IN
Voltage Offset Error
Voltage Gain Error
Temperature Error
Input Logic High:
DQ, PIO
Input Logic Low:
DQ, PIO
Output Logic Low:
DQ, PIO
DQ Pulldown Current
DQ Capacitance
DQ Low-to-Sleep Time
Undervoltage Detect
Undervoltage Delay
Internal Timebase
Accuracy
SYMBOL
I
ACTIVE
I
SLEEP
V
IS1-IS2
I
OERR
I
GERR
q
CA
f
SAMP
R
KS
R
IN
V
OERR
V
GERR
T
ERR
V
IH
V
IL
V
OL
I
PD
C
DQ
t
SLEEP
V
UV
t
UVD
t
ERR
(Note 1)
0°C to +50°C (Note 10)
-20°C to +70°C
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2.1
2.45
90
(Note 9)
(Note 1)
(Note 1)
I
OL
= 4mA
(Note 1)
1
60
2.5
100
±1
2.55
110
±2
±3
1.5
0.4
0.4
+25°C
V
IN
= V
DD
(Note 8)
5
±5
±2
±3
CONDITIONS
DQ = V
DD
, EEC bit = 0,
0°C to +50°C, 2.5V < V
DD
<
4.2V
DQ = V
DD,
EEC bit = 0
DQ = 0V (Note 3)
(Note 2)
(Note 5)
(Note 2, 6)
V
IS1-IS2
= 0, OBEN set,
(Note 2, 7, 4)
-200
-100
1456
10
(2.5V
≤
V
DD
≤
5.5V, T
A
= -20°C to +70°C.)
MIN TYP
MAX
UNITS
75
1
±64
±7.813
±1
0
100
110
2
μA
μA
mV
μV
%I
reading
µVhr
Hz
kΩ
MΩ
mV
%V
reading
°C
V
V
V
μA
pF
s
V
ms
%
DS2755: High-Accuracy Battery Fuel Gauge with Snapshot
ELECTRICAL CHARACTERISTICS—1-WIRE INTERFACE
PARAMETER
Snapshot Trigger 0
Snapshot Delay
STANDARD TIMING
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
Interrupt Time Low
OVERDRIVE TIMING
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
Interrupt Time Low
SYMBOL
t
SWL
t
SDLY
t
SLOT
t
REC
t
LOW0
t
LOW1
t
RDV
t
RSTH
t
RSTL
t
PDH
t
PDL
t
IL
t
SLOT
t
REC
t
LOW0
t
LOW1
t
RDV
t
RSTH
t
RSTL
t
PDH
t
PDL
t
IL
CONDITIONS
(2.5V
≤
V
DD
≤
5.5V, T
A
= -20°C to +70°C.)
MIN
TYP
MAX
UNITS
1
16
μs
80
100
120
μs
60
1
60
1
480
480
15
60
480
6
1
6
1
48
48
2
8
48
120
119
15
15
960
60
240
1920
16
16
2
2
80
6
24
192
μs
μs
μs
μs
μs
μs
μs
μs
μs
μs
μs
μs
μs
μs
μs
μs
μs
μs
μs
μs
EEPROM RELIABILITY SPECIFICATION
PARAMETER
Copy to EEPROM Time
EEPROM Copy
Endurance
Note 1:
Note 2:
Note 3:
Note 4:
Note 5:
SYMBOL
t
EEC
N
EEC
CONDITIONS
(Note 11)
(2.5V
≤
V
DD
≤
5.5V, T
A
= -20°C to +70°C.)
MIN
TYP
MAX
UNITS
2
50,000
10
ms
cycles
Note 6:
Note 7:
Note 8:
Note 9:
Note 10:
Note 11:
All voltages are referenced to V
SS
.
Specifications relative to V
IS1
- V
IS2
.
The DS2755 requires a maximum of 25µAH of charge to transition into sleep mode.
Summation of worst case time base and current measurement sampling errors.
Continuous offset cancellation corrects offset errors in the current measurement system. Individual values reported by the
Current register have a maximum offset of ±0.5 LSb’s (±7.8125μV). Individual values reported in the Average Current register
have a maximum offset of ±2 LSb’s (±7.8125μV).
Current Gain Error specifies the gain error in the Current register value compared to a reference voltage between IS1 and IS2.
The DS2755 does not compensate for sense resistor characteristics, and any error terms arising from the sense resistor should
be taken into account when calculating total current measurement error.
Achieving the 24 Hour Accumulated Current Error assumes positive offset accumulation blanking is enabled (OBEN bit set) and
can require a one time 3.5s in-system calibration after mounting to the printed circuit board. Variations in temperature and supply
voltage are compensated for by periodic offset corrections performed automatically during
Active
mode operation.
Voltage offset measurement is with respect to 4.2V at +25°C.
Self heating due to output pin loading and sense resistor power dissipation can alter the Temperature reading from ambient
conditions.
Typical value for t
ERR
valid at 3.7V and +25°C. t
ERR
applies to all internal timings (ex. f
SAMP
, t
SLEEP
, t
UVD
) except for the 1-Wire
Interface timings.
Four year data retention at +50°C.
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DS2755: High-Accuracy Battery Fuel Gauge with Snapshot
Figure 2.
FUNCTIONAL DIAGRAM
1-WIRE
INTERFACE
AND
ROM ID
THERMAL
SENSE
VOLTAGE
REFERENCE
LOCKABLE EEPROM
BLOCKS
SRAM
TEMPERATURE
VOLTAGE
BIAS
DQ
VDD
VIN
M
U
X
ADC
CURRENT
ACCUM. CURRENT
COMPARATORS
STATUS / CONTROL
PIO
IS1
TIMEBASE
IS2
-
+
SNS
chip ground
VSS
DETAILED PIN DESCRIPTION
PIN
1
2
3
4
5
6
7
8
NAME
VIN
VSS
PIO
VDD
IS1
IS2
SNS
DQ
DESCRIPTION
Battery voltage sense input. Voltage measurement performed on VIN input and
displayed in Voltage Register.
Device ground and current sense resistor connection. VSS attaches to battery end
of sense resistor.
General purpose programmable I/O pin or optional interrupt output.
Input supply: +2.5V to +5.5V input range. Bypass VDD to VSS with 0.1μF.
Current sense filter input 1
Current sense filter input 2
Sense resistor connection. SNS attaches to pack end of current sense resistor.
Serial interface data I/O pin. Bidirection data transmit and receive at 16kbps or
143kbps. Optional interrupt output.
POWER MODES
The DS2755 has two power modes:
Active
and
Sleep.
While in
Active
mode, the DS2755 continuously measures
current, voltage and temperature. Current accumulation and monitoring for under voltage also occur continuously in
Active
mode. In
Sleep
mode, the DS2755 ceases these activities. The DS2755 enters
Sleep
mode when PMOD =
1
AND
either of the following occur:
the DQ line is low for longer than t
SLEEP
(minimum 2.1s)
(DQ low used indicate that the pack has been disconnected or that the host system is signaling the
DS2755 to enter
Sleep
mode.)
the UVEN bit in the Status Register is set to 1
AND
the voltage on V
IN
drops below undervoltage threshold V
UV
for
t
UVD
The DS2755 returns to
Active
mode when the DQ line is pulled from a low-to-high state and the voltage on V
IN
is
above V
UV
. The factory default for the DS2755 is UVEN = PMOD = 0. The DS2755 defaults to
Active
mode when
power is first applied.
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