bq20851-V1P2
SLUS575 - AUGUST 2003
SBS COMPLIANT GAS GAUGE IC
FOR USE WITH THE bq29311
FEATURES
D
Provides Accurate Measurement of Available
Charge in Li-Ion and Li-Polymer Batteries
D
Supports the Smart Battery Specification
(SBS) V1.1
D
Integrated Time Base Removes Need for
External Crystal
D
Works With the TI bq29311 Analog Front End
(AFE) Protection IC to Provide Complete Pack
Electronics for 10.8-V or 14.4-V Battery Packs
With Few External Components
D
Based on a Powerful Low-Power RISC CPU
Core With High-Performance Peripherals
D
Integrated Flash Memory Eliminates the Need
for External Configuration EEPROM
D
Measures Charge Flow Using a High
Resolution 16-Bit Integrating Converter
- Better Than 3-nVh of Resolution
- Self-Calibrating
- Offset Error Less Than 1-
V
D
Uses 16-Bit Delta Sigma Converter for
Accurate Voltage and Temperature
Measurements
D
Programmable Cell Modeling for Maximum
Battery Fuel Gauge Accuracy
D
Drives 3-, 4-, or 5-Segment LED Display for
Remaining Capacity Indication
D
38-Pin TSSOP (DBT)
APPLICATIONS
D
Notebook PCs
DESCRIPTION
The bq20851-V1P2 SBS-compliant gas gauge IC for
battery pack installation maintains an accurate record of
available charge in Li-ion or Li-polymer batteries. The
bq20851-V1P2 monitors capacity and other critical
parameters of the battery pack and reports the information
to the system host controller over a serial communication
bus. It is designed to work with the bq29311 analog
front-end (AFE) protection IC to maximize functionality
and safety and minimize component count and cost in
smart battery circuits. Using information from the
bq20851-V1P2, the host controller can manage
remaining battery power to extend the system run time as
much as possible.
BLOCK DIAGRAM
ADC
Voltage
Sense
Resistor
(10 m
- 20 m
)
Pack-
Integrating
ADC
Coulomb
Counting
Temp
Sensor
512 Bytes
Config.
Flash
EPROM
bq20851-V1P2
Level
Translator
bq29311
LDO
Glueless
Interface
Cell Inputs
Safety Control
SMBus
Pack+
Supply Voltage
Li-Ion
Cells
-
+
Charge/Discharge
Power FETs
-
+
-
+
PRODUCTION DATA information is current as of publication date. Products
conform to specifications per the terms of Texas Instruments standard warranty.
Production processing does not necessarily include testing of all parameters.
Please be aware that an important notice concerning availability, standard warranty, and use in critical applications of Texas Instruments
semiconductor products and disclaimers thereto appears at the end of this data sheet.
www.ti.com
Copyright
2003, Texas Instruments Incorporated
bq20851-V1P2
SLUS575 - AUGUST 2003
www.ti.com
2
DESCRIPTION (CONTINUED)
The bq20851-V1P2 uses an integrating converter with
continuous sampling for the measurement of battery
charge and discharge currents. Optimized for coulomb
counting in portable applications, the self-calibrating
integrating converter has a resolution better than 3-nVh
and an offset measurement error of less than 1-
V
(typical). For voltage and temperature reporting, the
bq20851-V1P2 uses a 16-bit A-to-D converter. In
conjunction with the bq29311, the onboard ADC also
monitors individual cell voltages in a battery pack and
allows the bq20851-V1P2 to generate the control signals
necessary to implement the cell balancing and the
required safety protection for Li-ion and Li-polymer battery
chemistries.
The bq20851-V1P2 supports the Smart Battery Data
(SBData) commands and charge-control functions. It
communicates data using the System Management Bus
(SMBus) 2-wire protocol. The data available include the
battery's remaining capacity, temperature, voltage,
current, and remaining run-time predictions. The
bq20851-V1P2 provides LED drivers and a push-button
input to depict remaining battery capacity from full to empty
in 20%, 25%, or 33% increments with a 3-, 4-, or
5-segment display.
The bq20851-V1P2 contains 512 bytes of internal data
flash memory, which store configuration information. The
information includes nominal capacity and voltage,
self-discharge rate, rate compensation factors, and other
programmable cell-modeling factors used to accurately
adjust remaining capacity for use-conditions based on
time, rate, and temperature. The bq20851-V1P2 also
automatically calibrates or learns the true battery capacity
in the course of a discharge cycle from programmable near
full to near empty levels.
The bq29311 AFE protection IC provides power to the
bq20851-V1P2 from a 3 or 4 series Li-ion cell stack,
eliminating the need for an external regulator circuit.
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
38
37
36
35
34
33
32
31
30
29
28
27
26
25
24
23
22
21
20
VIN
TS
LED5
LED4
LED3
SCLK
N/C
VDDD
RBI
SDATA
VSSD
SAFE
N/C
N/C
SMBC
SMBD
DISP
EVENT
VSSD
VSSD
LED1
LED2
CLKOUT
VSSA
ROSC
FILT
VDDA
VSSA
VSSP
SR1
SR2
MRST
N/C
N/C
N/C
N/C
N/C
N/C
TSSOP PACKAGE
(TOP VIEW)
NC - No internal connection
AVAILABLE OPTIONS
TA
PACKAGE
38-PIN TSSOP
(DBT)
-20
C to 85
C
bq20851DBT-V1P2(1)
(1) The bq20851-V1P2 is available taped and reeled. Add an R suffix
to the device type (e.g., bq20851DBTR-V1P2) to order tape and
reel version.
bq20851-V1P2
SLUS575 - AUGUST 2003
www.ti.com
3
Terminal Functions
TERMINAL
I/O
DESCRIPTION
NAME
No.
I/O
DESCRIPTION
CLKOUT
35
I
32.768-kHz output to the bq29311
DISP
17
I
Display control for the LED drivers LED1 through LED5
FILT
32
I
Analog input connected to the external PLL filter
EVENT
18
I
Input from bq29311 XALERT output
LED1
37
O
LED2
36
O
LED3
5
O
LED display segments that each may drive an external LED
LED4
4
O
LED display segments that each may drive an external LED
LED5
3
O
MRST
26
I
Master reset input that forces the device into reset when held high
N/C
20-24, 7, 13,
14, 25,
-
No connection
RBI
9
I
Register backup that provides backup potential to the bq20851-V1P2 data registers during periods of low
operating voltage. RBI accepts a storage capacitor or a battery input.
ROSC
33
I
Internal time base bias input
SAFE
12
O
Output for additional level of safety protection; e.g., fuse blow.
SCLK
6
O
Communication clock to the bq29311
SDATA
10
I/O
Data transfer to and from bq29311
SMBC
15
I/O
SMBus clock open-drain bidirectional pin used to clock the data transfer to and from the bq20851-V1P2
SMBD
16
I/O
SMBus data open-drain bidirectional pin used to transfer address and data to and from the bq20851-V1P2
SR1
28
I
Connections for a small-value sense resistor to monitor the battery charge- and discharge-current flow
SR2
27
I
Connections for a small-value sense resistor to monitor the battery charge- and discharge-current flow
TS
2
I
Thermistor voltage input connection to monitor temperature
VDDA
31
I
Positive supply for analog circuitry
VDDD
8
I
Positive supply for digital circuitry and I/O pins
VIN
1
I
Single cell voltage input from the bq29311
VSSA
30, 34
I
Negative supply for analog circuitry
VSSD
11, 19, 38
I
Negative supply for digital circuitry
VSSP
29
I
Negative supply for output circuitry
bq20851-V1P2
SLUS575 - AUGUST 2003
www.ti.com
4
These devices have limited built-in ESD protection. The leads should be shorted together or the device placed in conductive foam during
storage or handling to prevent electrostatic damage to the MOS gates.
ABSOLUTE MAXIMUM RATINGS
over operating free-air temperature (unless otherwise noted)(1)
UNITS
Supply voltage range, VDD relative to VSS(2)
-0.3 V to 6 V
Open-drain I/O pins, V(IOD) relative to VSS (2)
-0.3 V to 6 V
Input voltage range to all other pins, VI relative to VSS (2)
-0.3 V to VDD + 0.3 V
Operating free-air temperature range, TA
-20
C to 85
C
Storage temperature range, Tstg
-65
C to 150
C
HBM
1.5 kV
ESD rating
CDM
1.5 kV
ESD rating
MM
50 V
(1) 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 under "recommended operating conditions" is not
implied. Exposure to absolute-maximum-rated conditions for extended periods may affect device reliability.
(2) VSS refers to the common node of V(SSA), V(SSD), and V(SSP).
ELECTRICAL CHARACTERISTICS
VDD = 3.0 V to 3.6 V, TA = -20
C to 85
C (unless otherwise noted)
PARAMETER
TEST CONDITIONS
MIN
TYP
MAX
UNIT
VDD
Supply voltage
VDDA and VDDD
3.0
3.3
3.6
V
IDD
Operating current
No flash programming
350
A
I(SLP)
Low-power storage mode current
Hibernate mode
1
A
V(OLS)
Output voltage low: (LED1-LED5)
I(OLS) = 10 mA
0.4
V
VIL
Input voltage low DISP
-0.3
0.8
V
VIH
Input voltage high DISP
2
VCC + 0.3
V
VOL
Output voltage low SMBC, SMBD, SDATA, SCLK,
EVENT, SAFE
IOL = 0.5 mA
0.4
V
V(ILS)
Input voltage low SMBC, SMBD, SDATA, SCLK,
EVENT, SAFE
-0.3
0.8
V
V(IHS)
Input voltage high SMBC, SMBD, SDATA, SCLK,
EVENT, SAFE
1.7
6
V
V(AI)
Input voltage range VIN, TS, OC
VSS - 0.3
1.0
V
Z(AI1)
Input impedance SR1, SR2
0 V1.0 V
10
M
Z(AI2)
Input impedance VIN, TS, OC
0 V1.0 V
8
M
Power-On Reset (see Figure 1)
PARAMETER
TEST CONDITIONS
MIN
TYP
MAX
UNIT
VIT-
Negative-going voltage input
2.1
2.3
2.5
V
Vhys
Power-on reset hysteresis
50
125
210
mV
bq20851-V1P2
SLUS575 - AUGUST 2003
www.ti.com
5
Figure 1
Vhys
VIT-
TA - Free-Air Temperature -
C
POR BEHAVIOR
vs
FREE-AIR TEMPERATURE
- Negative-Going Input Threshold V
oltage - V
V
IT-
- Hysteresis V
oltage - mV
V
hys
2.50
2.45
2.40
2.35
2.30
2.25
2.20
2.15
2.10
-20
-5
10
25
40
55
70
85
150
145
140
135
130
125
120
115
110
INTEGRATING ADC CHARACTERISTICS
VDD = 3.0 V to 3.6 V, TA = -20
C to 85
C (unless otherwise noted)
PARAMETER
TEST CONDITIONS
MIN
TYP
MAX
UNIT
V(SR)
Input voltage range, V(SR2) and V(SR1)
VSR = V(SR2) V(SR1)
0.3
1.0
V
V(SROS)
Input offset
1
V
INL
Integral nonlinearity error
0.003%
0.009%
PLL SWITCHING CHARACTERISTICS
VDD = 3.0 V to 3.6 V, TA = -20
C to 85
C (unless otherwise noted)
PARAMETER
TEST CONDITIONS
MIN
TYP
MAX
UNIT
t(sp)
Start-up time(1)
0.5% frequency error
2
5
ms
(1) The frequency error is measured from 32.768 Hz.
Internal Oscillator
VDD = 3.0 V to 3.6 V, TA = -20
C to 85
C (unless otherwise noted)
PARAMETER
TEST CONDITIONS
MIN
TYP
MAX
UNIT
f(exo)
Frequency error(1)
-2%
2%
f(exo)
Frequency error(1)
VDD = 3.3 V
-1%
1%
f(sxo)
Start-up time(2)
275
s
(1) The frequency error is measured from 32.768 Hz.
(2) The start-up time is defined as the time it takes for the oscillator output frequency to be
1%.
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