19-4639; Rev 2; 5/09
Stand-Alone Fuel-Gauge IC with
LED Display Drivers
General Description
The DS2788 measures voltage, temperature, and cur-
rent, and estimates available capacity for rechargeable
lithium-ion (Li+) and Li+ polymer batteries. Cell charac-
teristics and application parameters used in the calcu-
lations 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 cur-
rent temperature, discharge rate, stored charge, and
application parameters. Capacity estimation is reported
in mAh remaining and percentage of full.
LED display drivers and a debounced input make dis-
play of the capacity information easy. The LED pins can
directly sink current, requiring only a resistor for setting
the current in the LED display, thus reducing space and
cost.
Features
♦
Five 30mA Open-Drain Drivers for Driving LED
Fuel-Gauge Display
♦
Debounced Fuel-Gauge Display Enable
♦
Internal Voltage Measurement Gain Register for
Trimming External Voltage-Divider
♦
Pin for Driving FETs to Enable Voltage-Divider
Only During Voltage Measurement, Conserving
Power
♦
Precision Voltage, Temperature, and Current
Measurement System
♦
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
♦
14-Pin TSSOP Package
DS2788
Applications
Power Tools
Electric Bicycles
Electric Vehicles
Uninterruptible Power Supply
Digital Cameras
Pin Configuration
TOP VIEW
+
LED2
LED1
DV
SS
V
DD
OVD
V
SS
DQ
1
2
3
4
5
6
7
14
13
12
LED3
LED4
LED5
PIO
V
IN
SNS
VMA
Ordering Information
PART
DS2788E+
DS2788E+T&R
TEMP RANGE
-25°C to +70°C
-25°C to +70°C
PIN-PACKAGE
14 TSSOP
14 TSSOP
DS2788
11
10
9
8
+Denotes
a lead(Pb)-free/RoHS-compliant package.
T&R = Tape and reel.
TSSOP
Typical Operating Circuit appears at end of data sheet.
1-Wire is a registered trademark of Maxim Integrated Products, Inc.
________________________________________________________________
Maxim Integrated Products
1
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.
Stand-Alone Fuel-Gauge IC with
LED Display Drivers
DS2788
ABSOLUTE MAXIMUM RATINGS
Voltage Range on Any Pin Relative to V
SS..............
-0.3V to +6.0V
Voltage Range on V
IN
, VMA Relative to V
SS ...
-0.3V to V
DD
+ 0.3V
DV
SS
to V
SS .....................................................................
-0.3V to +0.3V
LED1–5.................................................................60mA each pin
Operating Temperature Range ...........................-40°C to +85°C
Storage Temperature Range .............................-55°C to +125°C
Soldering Temperature (10s) ................Refer to IPC/JEDEC-020
Specification.
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
absolute maximum rating conditions for extended periods may affect device reliability.
RECOMMENDED DC OPERATING CHARACTERISTICS
(V
DD
= 2.5V to 4.5V, T
A
= -25°C to +70°C, unless otherwise noted. Typical values are at T
A
= +25°C.)
PARAMETER
Supply Voltage
V
IN
, VMA Voltage Range
DQ, PIO, OVD, LED1–LED5
Voltage Range
SYMBOL
V
DD
(Note 1)
(Note 1)
(Note 1)
CONDITIONS
MIN
+2.5
0
0
TYP
MAX
+4.5
V
DD
+5.5
UNITS
V
V
V
DC ELECTRICAL CHARACTERISTICS
(V
DD
= 2.5V to 4.5V, T
A
= -25°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, VMA
Output Logic-High: VMA
VMA Precharge Time
Pulldown Current: DQ, PIO
Output Logic-Low: LED1–LED5
Input Logic-High: OVD
Input Logic-Low: OVD
V
IN
Input Resistance
DQ SLEEP Timeout
Undervoltage SLEEP Threshold
PIO Switch Debounce
LED1 Display Blink Rate
LED Display-On Time
50% duty cycle
SYMBOL
I
ACTIVE
I
SLEEP
V
IH
V
IL
V
OL
V
OH
t
PRE
I
PD
V
OL
V
IH
V
IL
R
IN
t
SLEEP
V
SLEEP
DQ < V
IL
(Note 1)
V
DQ
, V
PIO
= 0.4V
I
OL
= -30mA (Note 1)
(Note 1)
(Note 1)
15
1.8
2.40
100
0.9
3.6
1.0
4.0
2.0
2.45
2.2
2.50
130
1.1
4.4
V
DD
-
0.2
V
SS
+
0.2
(Note 1)
(Note 1)
I
OL
= 4mA (Note 1)
I
OH
= 1mA (Note 1)
V
DD
-
0.5
13.3
0.2
14.2
5
1
1.5
0.6
0.4
2.5V
V
DD
CONDITIONS
4.2V
MIN
TYP
70
1
MAX
95
105
3
UNITS
μA
μA
V
V
V
V
ms
μA
V
V
V
M
s
V
ms
Hz
s
2
_______________________________________________________________________________________
Stand-Alone Fuel-Gauge IC with
LED Display Drivers
ELECTRICAL CHARACTERISTICS: TEMPERATURE, VOLTAGE, CURRENT
(V
CC
= 2.5V to 4.5V, T
A
= -25°C to +70°C, unless otherwise noted. Typical values are at T
A
= +25°C.)
PARAMETER
Temperature Resolution
Temperature Error
Voltage Resolution
Voltage Full-Scale
Voltage Error
Current Resolution
Current Full-Scale
Current Gain Error
Current Offset Error
Accumulated Current Offset
SYMBOL
T
LSB
T
ERR
V
LSB
V
FS
V
ERR
I
LSB
I
FS
I
GERR
I
OERR
q
OERR
(Note 2)
0°C T
A
+70°C, 2.5V
(Notes 3, 4)
V
DD
4.2V
4.2V,
-7.82
-188
1.56
±51.2
±1
+12.5
0
±1
4.2V
±2
±3
%
0
4.88
4.5
±50
CONDITIONS
MIN
TYP
0.125
±3
MAX
UNITS
°C
°C
mV
V
mV
μV
mV
% Full
Scale
μV
μVhr/
day
DS2788
0°C T
A
+70°C, 2.5V V
DD
V
SNS
= V
SS
(Notes 3, 4, 5)
V
DD
= 3.8V, T
A
= +25°C
0°C T
A
+70°C, 2.5V V
DD
Timebase Error
t
ERR
ELECTRICAL CHARACTERISTICS: 1-Wire INTERFACE, STANDARD
(V
CC
= 2.5V to 4.5V, T
A
= -25°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
μs
μs
μs
μs
μs
μs
μs
μs
μs
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3
Stand-Alone Fuel-Gauge IC with
LED Display Drivers
DS2788
ELECTRICAL CHARACTERISTICS: 1-Wire INTERFACE, OVERDRIVE
(V
CC
= 2.5V to 4.5V, T
A
= -25°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
μs
μs
μs
μs
μs
μs
μs
μs
μs
EEPROM RELIABILITY SPECIFICATION
(V
CC
= 2.5V to 4.5V, T
A
= -25°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 (Note 6)
50,000
CONDITIONS
MIN
TYP
MAX
10
UNITS
ms
Cycles
Note 1:
Note 2:
Note 3:
Note 4:
Note 5:
Note 6:
All voltages are referenced to V
SS
.
Factory-calibrated accuracy. Higher accuracy can be achieved by in-system calibration by the user.
Parameters guaranteed by design.
At a constant regulated V
DD
voltage, the Current Offset Bias register can be used to obtain higher accuracy.
Accumulation Bias register set to 00h.
EEPROM data retention is 10 years at +50°C.
4
_______________________________________________________________________________________
Stand-Alone Fuel-Gauge IC with
LED Display Drivers
Pin Description
PIN
1
2
3
4
5
6
7
8
9
10
11
NAME
LED2
LED1
DV
SS
V
DD
OVD
V
SS
DQ
VMA
SNS
V
IN
PIO
FUNCTION
Display Driver. Connect to an LED connected to V
DD
for display of relative pack capacity.
Display Driver. Connect to an LED connected to V
DD
for display of relative pack capacity.
Display Ground. Ground connection for the LED display drivers. Connect to V
SS
.
Power-Supply Input. Connect to the positive terminal of the battery cell through a decoupling network.
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 (STD) timing. On a multidrop bus, all devices must operate at the same speed.
Device Ground. Connect directly to the negative terminal of the battery cell. Connect the sense resistor
between V
SS
and SNS.
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.
Voltage Measurement Active. Output is driven high before the start of a voltage conversion and driven low at
the end of the conversion cycle.
Sense Resistor Connection. Connect to the negative terminal of the battery pack. Connect the sense resistor
between V
SS
and SNS.
Voltage Sense Input. The voltage of the battery cell is monitored through this input pin.
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 a weak internal pulldown (I
PD
). When configured as an input,
upon recognition of a rising edge, the fuel-gauge display is enabled.
Display Driver. Connect to an LED connected to V
DD
for display of relative pack capacity. Leave floating in
LED4 configuration.
Display Driver. Connect to an LED connected to V
DD
for display of relative pack capacity.
Display Driver. Connect to an LED connected to V
DD
for display of relative pack capacity.
DS2788
12
13
14
LED5
LED4
LED3
V
DD
LED5
LED4
LED3
LED2
LED1
DV
SS
EN
V
POR
PIO
DQ
OVD
BIAS/VREF
TIME BASE
LED
DRIVERS
STATUS
AND
CONTROL
1-Wire
INTERFACE
TEMP
AND
VOLTAGE
ADC
VMA
V
IN
EEPROM
DS2788
SNS
ACCUMULATED
CURRENT
CURRENT ADC
15-BIT + SIGN
RATE AND
TEMPERATURE
COMPENSATION
V
SS
Figure 1. Block Diagram
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5
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