TI bq28550DRZR

bq28550
SLUSAJ2 – SEPTEMBER 2011
www.ti.com
bq28550 Single Cell Li-Ion Battery Gas Gauge and Protection
Check for Samples: bq28550
FEATURES
1
•
•
•
A Comprehensive Single-Cell Li-Ion Battery
Manager Integrates All Essential Functions
– Gas Gauge
– Low-Side N-CH FET Protection Control
– JEITA/Enhanced Charging
– Authentication
Battery Gas Gauge Information
Protection Functions Include:
– Short-Circuit
– Overcurrent Charge and Discharge
– Overvoltage Charge (Overcharge)
•
•
•
– Undervoltage (Over-Discharge)
– Firmware Control of Discharge FET
SHA-1/HMAC Battery Authentication
SMBus Communications Interface
12-pin, 2.5-mm x 4.0-mm SON Package
APPLICATIONS
•
•
•
•
•
Tablet PCs
Slates
Digital Still and Video Cameras
Handheld Terminals
MP3 or Multimedia Players
DESCRIPTION
The Texas Instruments bq28550 battery gas gauge provides current and voltage protection, and secure,
SHA-1/HMAC authentication for single-cell Li-Ion battery packs. Designed for battery-pack integration, the
bq28550 requires host microcontroller firmware support for implementation. A system processor communicates
with the bq28550 using one of the serial interface configurations to obtain remaining battery capacity, system
run-time predictions, and other critical battery information.
The bq28550 uses an accurate gas gauging algorithm to report the status of the cell. The gauge provides
information such as state-of-charge (%), run-time to empty (min.), charge-time to full (min.), battery voltage (V),
and pack temperature (°C).
The bq28550 also features integrated support for secure battery-pack authentication, using the SHA-1/HMAC
authentication algorithm.
DOUT
1
12
NC
COUT
2
11
SCL
VM
3
10
SDA
BAT
4
9
TS
VREG
5
8
SRN
VSS
6
7
SRP
bq28550
Figure 1. Top View
1
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.
PRODUCTION DATA information is current as of publication date.
Products conform to specifications per the terms of the Texas
Instruments standard warranty. Production processing does not
necessarily include testing of all parameters.
Copyright © 2011, Texas Instruments Incorporated
bq28550
SLUSAJ2 – SEPTEMBER 2011
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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.
Table 1. ORDERING INFORMATION (1)
TA
–40°C to 85°C
(1)
PART NUMBER
PACKAGE
TAPE AND REEL QUANTITY
bq28550DRZR
12-pin, 2.5-mm × 4.0-mm
SON
3000
bq28550DRZT
250
For the most current package and ordering information, see the Package Option Addendum at the end of this document, or visit the
device product folder on ti.com (www.ti.com).
THERMAL INFORMATION
bq28550
THERMAL METRIC
(1)
SON
UNITS
12 PINS
θJA
Junction-to-ambient thermal resistance (2)
θJC(top)
Junction-to-case(top) thermal resistance
186.4
(3)
90.4
(4)
θJB
Junction-to-board thermal resistance
ψJT
Junction-to-top characterization parameter
ψJB
Junction-to-board characterization parameter
θJC(bottom)
(1)
(2)
(3)
(4)
(5)
(6)
(7)
110.7
(5)
Junction-to-case(bottom) thermal resistance
96.7
(6)
°C/W
90
(7)
n/a
For more information about traditional and new thermal metrics, see the IC Package Thermal Metrics application report, SPRA953.
The junction-to-ambient thermal resistance under natural convection is obtained in a simulation on a JEDEC-standard, high-K board, as
specified in JESD51-7, in an environment described in JESD51-2a.
The junction-to-case (top) thermal resistance is obtained by simulating a cold plate test on the package top. No specific
JEDEC-standard test exists, but a close description can be found in the ANSI SEMI standard G30-88.
The junction-to-board thermal resistance is obtained by simulating in an environment with a ring cold plate fixture to control the PCB
temperature, as described in JESD51-8.
The junction-to-top characterization parameter, ψJT, estimates the junction temperature of a device in a real system and is extracted
from the simulation data for obtaining θJA, using a procedure described in JESD51-2a (sections 6 and 7).
The junction-to-board characterization parameter, ψJB, estimates the junction temperature of a device in a real system and is extracted
from the simulation data for obtaining θJA , using a procedure described in JESD51-2a (sections 6 and 7).
The junction-to-case (bottom) thermal resistance is obtained by simulating a cold plate test on the exposed (power) pad. No specific
JEDEC standard test exists, but a close description can be found in the ANSI SEMI standard G30-88.
PIN DETAILS
Table 2. Pin Descriptions
2
PIN NUMBER
PIN NAME
I/O (1)
1
DOUT
IA
The output of gate drive for discharge FET
DESCRIPTION
2
COUT
IA
The output of gate drive for charge FET
3
VM
IA
Analog input pin connected to the PACKN through a 510-Ω resistor. Overcurrent
and short-circuit protection circuits use the voltage across VM and VSS to detect if
excessive charge or discharge current is flowing through the protection FETs.
4
BAT
IA
Cell voltage measurement input. ADC input. Connect a 0.1-µF ceramic capacitor to
VSS.
5
VREG
P
2.5-V output voltage of the internal integrated LDO. Connect a 0.1-µF ceramic
capacitor to VSS.
6
VSS
P
Device ground
7
SRP
IA
Analog input pin connected to the internal coulomb counter where SRP is nearest
the CELL-connection. Connect to 5-mΩ to 20-mΩ sense resistor.
8
SRN
IA
Analog input pin connected to the internal coulomb counter where SRN is nearest
the PACKN connection. Connect to 5-mΩ to 20-mΩ sense resistor.
9
TS
IA
Pack thermistor voltage sense (use 103AT-type thermistor), ADC input
10
SDA
I/O
Serial Data interface for SMBus
11
SCL
I
Serial Clock interface for SMBus
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Table 2. Pin Descriptions (continued)
PIN NUMBER
PIN NAME
I/O (1)
12
NC
I/O
Pull up to VREG with 3.3-K resistor
DESCRIPTION
13
PWPD
I/O
Thermal Pad. Connect to VSS externally on PCB.
FUNCTIONAL BLOCK DIAGRAM
FUSE
PACK +
SCL
SDA
3.3 K
DOUT 1
VM
BAT
510
2
3
11
10
bq28550
4
9
VREG 5
8
0.1 µF
VSS 6
0.1 µF
SCL
100
SDA
100
100
VREG
CELLP
TS
CELLN
SRN
7 SRP
13
PWPD
0.1 µF
0.1 µF
COUT
100
NC
12
PACK –
D
S
CHG
100
100
0.1 µF
S
10 mW
DSG
Figure 2. Block Diagram
ABSOLUTE MAXIMUM RATINGS
All voltages are referenced to the VSS pin. Over operating free-air temperature range (unless otherwise noted)
PARAMETER
VBAT
Regulator input voltage, BAT (Pin 4)
VVM
(1)
VALUE
UNIT
–0.3 V to 6
V
VM terminal voltage (Pin 3)
VBAT – 32 to VBAT + 0.3
V
VCOUT
COUT terminal input voltage (Pin 2)
VBAT – 32 to VBAT + 0.3
V
VDOUT
DOUT terminal input voltage (Pin 1)
VSS – 0.3 to VBAT + 0.3
V
–0.3 to 6
V
V
VIOD
All other pins (Pins 5, 7, 8, and 9)
(1)
VSDATA
SDA (Pin 10)
VSS – 0.3 to VBAT + 0.3
VSCLK
SCL (Pin 11)
VSS – 0.3 to VBAT + 0.3
V
ESD
Human body model
±2
kV
ESD
Machine model
±200
V
TA
Operating free-air temperature range
–40°C to 85
°C
Tstg
Storage temperature range
–65°C to 150
°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 under “recommended operating
conditions” is not implied. Exposure to absolute–maximum–rated conditions for extended periods may affect device reliability.
RECOMMENDED OPERATING CONDITIONS
TA = 25ºC, VBAT = 3.6 V (unless otherwise noted)
PARAMETER
VBAT
TEST CONDITIONS
BAT pin 4 input
MIN
TYP
MAX
UNIT
2.45
3.6
5.5
V
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RECOMMENDED OPERATING CONDITIONS (continued)
TA = 25ºC, VBAT = 3.6 V (unless otherwise noted)
PARAMETER
ICC
TEST CONDITIONS
MIN
TYP
Normal operating
mode
Gas gauge in NORMAL mode. ILOAD > Sleep
Current
141
Low-power
(SLEEP)
Gas gauge in SLEEP mode. ILOAD < Sleep
Current
70
Sleep (FULL
SLEEP)
Gas gauge in FULLSLEEP mode. ILOAD < Sleep
Current
31
Hibernate
Gas gauge in HIBERNATE mode. ILOAD <
Hibernate Current
16
Shutdown
Gas gauge in SHUTDOWN mode
1
MAX
UNIT
µA
ISS
Maximum current
CREG
Regulator output
capacitor
CBAT
VBAT input filter
capacitor
0.1
µF
RPACKN
Resistor from VM
to PACKN
510
Ω
RPU_
SCL, SDA pull up
resistor
3.3
kΩ
VPU_
SCL, SDA pull up
voltage
2.5
4.2
V
VIL_
SDA and SCL Input Reference to VSS, VBAT = 2.5 V
voltage low
–0.5
0.3 VBAT
V
VIH_
SDA and SCL Input Reference to Vss, VBAT = 2.5 V
voltage high
0.7 VBAT
V
VHYS
Hysteresis
0.05 VBAT
V
VOL_
SDA output voltage Reference to VSS, VBAT = 2.5 V. IOH = 3 mA (open
low
drain)
CI
Capacitance for
each I/O pin
tPUCD
Power Up
Communication
Delay
VAI2
Input voltage range
(SRP, SRN)
20
Reference to VSS, VBAT = 2.5 V, fSCL = 400 kHz
(fast mode)
mA
µF
0.1
0
SDA and SCL input capacitance
0.4
V
10
pF
250
VSS – 0.25
ms
0.25
V
BATTERY PROTECTION
TA = –40 to +85ºC, VBAT =1.5 V to 5.5 V; Typical values stated, where TA = 25ºC and VBAT =3.6 V (unless otherwise noted)
PARAMETER
4
TEST CONDITION
MIN
NOM
MAX
UNIT
1.2
V
VST
Minimum operating
voltage for 0 V
charging
VST = VBAT – VM
RSHORT
Overcurrent release
resistance
VBAT = 4.0 V, VM = 1 V
30
50
100
kΩ
RDS
DS pin pull-down
resistance
VBAT = 4.0 V
6.5
13.0
26.0
kΩ
VOL1
COUT Low Level
Output voltage
(referenced to VM)
IOL = 30 µA, VBAT = 4.5 V
0.4
0.5
V
VOH1
COUT High Level
Output voltage
(referenced to VM)
IOH = 30 µA, VBAT = 4.0 V
VOL2
DOUT Low Level
Output voltage
(referenced to Vss)
IOL = 30 µA, VBAT = 2.0 V
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3.4
3.7
0.2
V
0.5
V
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BATTERY PROTECTION (continued)
TA = –40 to +85ºC, VBAT =1.5 V to 5.5 V; Typical values stated, where TA = 25ºC and VBAT =3.6 V (unless otherwise noted)
PARAMETER
TEST CONDITION
MIN
NOM
3.4
3.7
MAX
VOH2
DOUT High Level
Output voltage
(referenced to Vss)
IOH = 30 µA, VBAT = 4.0 V
VDET1
Overcharge
detection
TA = 25˚C detection voltage
4.260
4.280
4.300
TA = –10 to 60˚C
4.255
4.280
4.305
TA = –40 to 85˚C
4.230
4.280
4.330
TA = 25˚C
4.070
4.100
4.130
TA = –10 to 60˚C
4.055
4.100
4.145
TA = –40 to 85˚C
4.040
4.100
4.160
VREL1
Overcharge release
voltage
UNIT
V
V
V
tDET1
Overcharge
detection delay time
VBAT = 3.5 V ≥ 4.5 V
0.60
1.00
1.50
s
tREL1
Overcharge release
delay time
VBAT = 4.5 V ≥ 3.5 V
4.8
8.0
12.0
ms
VDET2
Over-discharge
detection voltage
TA = 25˚C
2.265
2.300
2.335
V
TA = –10 to 60˚C
2.242
2.300
2.358
TA = –40 to 85˚C
2.220
2.300
2.380
tDET2
Over-discharge
detection delay time
VBAT = 3.5 V ≥ 2.00 V
14.4
24.0
36.0
ms
tREL2
Over-discharge
release delay time
VBAT = 3 V
V_ = 3 V ≥ 0 V
2.4
4.0
6.0
ms
VDET3
Overcurrent
VBAT = 4 V
detection voltage on
discharge
0.130
0.150
0.170
V
VDET4
Overcurrent
VBAT = 4 V
detection voltage on
charging
–0.137
–0.112
–0.087
V
tOCD
Overcurrent
detection delay time
VBAT = 3 V
V_ = 0 V ≥ 1V
7.2
12.0
18.0
ms
tOCR
Overcurrent release
delay time
VBAT = 3 V
V_ = 3 V ≥ 0 V
2.4
4.0
6.0
ms
VSHORT
Short detection
voltage
VBAT = 4 V, RPACKN = 510 Ω
VBAT – 1.2
VBAT – 0.9
VBAT –
0.6
V
tSHORT
Short detection
delay time
VBAT = 3 V
V_ = 0V ≥ 3 V
200
400
800
µs
VOLTAGE REGULATOR
TA = –40 to +85ºC, VBAT =1.5 V to 5.5 V; Typical values stated, where TA = 25ºC and VBAT =3.6 V (unless otherwise noted)
PARAMETER
VREG
Output voltage
TEST CONDITIONS
MIN
TYP
MAX
UNIT
2.7 V < VBAT < 5.5 V, IOUT = 16 mA
2.45
2.50
2.55
V
2.45 V < VBAT < 2.7 V, IOUT = 3 mA
2.40
ΔVLINE
Line regulation
2.7 V< VBAT < 5.5 V, IOUT = 16 mA
100
200
mV
ΔVLOAD
Load regulation
VREG = 2.45 V, 100 µA < IOUT < 3 mA
30
50
mV
VBAT = 2.7 V, 3 mA < IOUT < 16 mA
30
50
VDO
ΔVREG/ΔT
ΔVLINE
VOFF
Dropout voltage
VBAT = 2.45 V, IOUT = 3 mA
30
50
VBAT = 2.7 V, IOUT = 16 mA
224
290
Output voltage
temperature
coefficient
VBAT = 3.5 V, IOUT = 100 µA
100
Current limit
VBAT = 3.5 V, IREG = 2.0 V
16
VBAT = 3.5 V, IREG = 0 V
10
35
60
7.0
8.0
9.0
Regulator off voltage
mV
ppm/°C
130
mA
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VOLTAGE REGULATOR (continued)
TA = –40 to +85ºC, VBAT =1.5 V to 5.5 V; Typical values stated, where TA = 25ºC and VBAT =3.6 V (unless otherwise noted)
PARAMETER
TEST CONDITIONS
MIN
Regulator off voltage VBAT = 3.6 V → 5.5 V, Rload = 100 Ω
delay time
VREG = 2.5 V → 2.3 V, Cload = 0.1 µF,
TA = 25°C
tVOFF
TYP
MAX
UNIT
50
100
µs
POWER-ON RESET
TA = –40 to +85ºC; Typical Values at TA = 25ºC (unless otherwise noted)
PARAMETER
VIT+
TEST CONDITIONS
Positive-going battery
voltage input at VREG
VHYS
MIN
TYP
MAX
UNIT
No external loading on VREG
2.125
2.200
2.275
V
No external loading on VREG
75
125
175
mV
INTERNAL TEMPERATURE SENSOR CHARACTERISTICS
TA = –40 to +85ºC; VBAT = 2.7 V to 5.5 V; Typical values stated, where TA = 25ºC and VBAT = 3.6 V (unless otherwise noted)
PARAMETER
GTEMP
TEST CONDITIONS
MIN
TYP
MAX
–2
Temperature Sensor
Voltage Gain
UNIT
mV/°C
HIGH FREQUENCY OSCILLATOR
TA = –40 to +85ºC, VBAT = 2.7 V to 5.5 V; Typical values stated, where TA = 25ºC and VBAT = 3.6 V (unless otherwise noted)
PARAMETER
f(OSC)
Operating frequency
f(EIO)
Frequency error
t(SXO)
(1)
(2)
(3)
TEST CONDITIONS
Start-up time
MIN
TYP
MAX
2.097
(1) (2)
,
UNIT
MHz
TA = 0°C to 60°C
–2.0
0.38
2.0
%
TA = –20°C to 70°C
–3.0
0.38
3.0
%
TA = –40°C to 85°C
–4.5
0.38
4.5
%
2.5
5
ms
(3)
The frequency error is measured from 2.097 MHz.
The frequency drift is included and measured from the trimmed frequency at VCC = 2.5 V, TA = 25°C.
The startup time is defined as the time it takes for the oscillator output frequency to be ±3%.
LOW FREQUENCY OSCILLATOR
TA = –40 to +85ºC, VBAT = 2.7 V to 5.5 V; Typical values stated, where TA = 25ºC and VBAT = 3.6 V (unless otherwise noted)
PARAMETER
f(LOSC)
f(LEIO)
Frequency error
(1)
(2)
t(LSXO)
(1)
(2)
(3)
TEST CONDITIONS
MIN
Operating frequency
Start-up time
,
TYP
MAX
32.768
UNIT
kHz
TA = 0°C to 60°C
–1.5
0.25
1.5
%
TA = –20°C to 70°C
–2.5
0.25
2.5
%
TA = –40°C to 85°C
–4.0
0.25
4.0
%
500
μs
(3)
The frequency drift is included and measured from the trimmed frequency at VCC = 2.5 V, TA = 25°C.
The frequency error is measured from 32.768 kHz.
The startup time is defined as the time it takes for the oscillator output frequency to be ±3%.
INTEGRATING ADC (COULOMB COUNTER) CHARACTERISTICS
TA = –40 to +85ºC, VBAT = 2.7 V to 5.5 V; Typical values stated, where TA = 25ºC and VBAT = 3.6 V (unless otherwise noted)
PARAMETER
VIN(SR)
tCONV(SR)
TEST CONDITIONS
Input voltage range, VSR = V(SRN) – V(SRP)
V(SRN) and V(SRP)
Conversion time
Single conversion
Resolution
VOS(SR)
6
MIN
TYP
–0.125
10
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UNIT
V
15
bits
1
14
Input offset
MAX
0.125
s
µV
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INTEGRATING ADC (COULOMB COUNTER) CHARACTERISTICS (continued)
TA = –40 to +85ºC, VBAT = 2.7 V to 5.5 V; Typical values stated, where TA = 25ºC and VBAT = 3.6 V (unless otherwise noted)
PARAMETER
INL
(1)
TEST CONDITIONS
MIN
Integral nonlinearity
error
ZIN(SR)
Effective input
resistance (1)
Ilkg(SR)
Input leakage
current (1)
TYP
MAX
UNIT
±0.007
±0.034
FSR
2.5
MΩ
µA
0.3
Specified by design. Not production tested.
ADC (TEMPERATURE AND CELL VOLTAGE) CHARACTERISTICS
TA = –40 to +85ºC, VBAT = 2.7 V to 5.5 V; Typical values stated, where TA = 25ºC and VBAT = 3.6 V (unless otherwise noted)
PARAMETER
VIN(ADC)
tCONV(ADC)
TEST CONDITIONS
TYP
Conversion time
Resolution
VOS(ADC)
MIN
–0.2
Input voltage range
14
Input offset
Effective input
resistance (TS)
V
125
ms
15
bits
Z(ADC2)
Effective input
resistance (BAT)
(1)
(1)
bq28550 is not measuring cell voltage.
mV
8
MΩ
8
MΩ
bq28550 is measuring cell voltage.
(1)
UNIT
1
1
Z(ADC1)
Ilkg(ADC)
MAX
100
Input leakage
current (1)
kΩ
µA
0.3
Specified by design. Not production tested.
DATA FLASH MEMORY CHARACTERISTICS
TA = –40 to +85ºC, VBAT = 2.7 V to 5.5 V; Typical values stated, where TA = 25ºC and VBAT = 3.6 V (unless otherwise noted)
PARAMETER
tDR
Data retention
TEST CONDITIONS
(1)
Flash programming
write-cycles (1)
tWORDPROG
Word programming
time (1)
ICCPROG
Flash-write supply
current (1)
(1)
MIN
TYP
MAX
UNIT
10
Years
20,000
Cycles
5
2
ms
10
mA
Specified by design. Not production tested.
SERIAL COMMUNICATION TIMING CHARACTERISTICS
TA = –40 to +85ºC, VBAT = 2.7 V to 5.5 V; Typical values stated, where TA = 25ºC and VBAT = 3.6 V (unless otherwise noted).
Capacitance on serial interface pins SCL and SDA are 10 pF unless otherwise specified (1).
PARAMETER
MIN
TYP
MAX
UNIT
tr
SCL/SDA rise time
300
ns
tf
SCL/SDA fall time
300
ns
tw(H)
SCL pulse width
(high)
600
ns
tw(L)
SCL pulse width
(low)
1.3
μs
Setup for repeated
start
600
ns
tsu(STA)
(1)
TEST CONDITIONS
Parameters assured by worst case test program execution in fast mode.
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SERIAL COMMUNICATION TIMING CHARACTERISTICS (continued)
TA = –40 to +85ºC, VBAT = 2.7 V to 5.5 V; Typical values stated, where TA = 25ºC and VBAT = 3.6 V (unless otherwise noted).
Capacitance on serial interface pins SCL and SDA are 10 pF unless otherwise specified (1).
PARAMETER
TEST CONDITIONS
td(STA)
Start to first falling
edge of SCL
tsu(DAT)
th(DAT)
MIN
TYP
MAX
UNIT
600
ns
Data setup time
1
μs
Data hold time
0
ns
tsu(STOP)
Setup time for stop
600
ns
t(BUF)
Bus free time
between stop and
start
1.3
μs
f(SCL)
Clock frequency
100
tsu (STA)
tw(L)
tw(H)
tf
tr
kHz
t(BUF)
SCL
SDA
td (STA)
tr
th (DAT)
tsu (DAT)
tf
REPEATED
START
tsu(STOP)
STOP
START
Figure 3. Timing
SERIAL 2-WIRE COMMUNICATION SYSTEM
The 2-wire communication bus supports a slave-only device in a single- or multi-slave configuration with a singleor multi-master configuration. The device can be part of a shared bus by the unique setting of the 7-bit slave
address. The 2-wire communication is bi-directional, consisting of a serial data line (SDA) and a clock line (SCL).
In receive mode, the SDA terminal operates as an input; whereas, when the device is returning data to the
master, the SDA operates as an open drain output with an external resistive pull-up. The master device controls
the initiation of the transaction on the bus line.
Data Transfer: Each data bit is transferred during an SCL clock cycle (transition from low-to-high and then
high-to-low). The data signal on the SDA (logic level) must be stable during the high period of the SCL clock
pulse. A change in the SDA logic when SCL is high is interpreted as a START or STOP control signal. If a
transfer is interrupted by a stop condition, the partial byte transmission shall not be latched. Only the prior
messages transmitted and acknowledged are latched.
Data Format: The data is an 8-bit format with the most significant bit (MSB) first and the least significant bit
(LSB) followed by an Acknowledge bit. If the slave cannot receive or transmit any byte of data until it services a
priority interrupt, it can pull the SCL line low to force the master device into wait state. The slave, once ready to
resume data transfer, can release the SCL line (get out of wait state).
Bus Idle: The bus is considered idle or busy when no master device has control of this device. The SDA and
SCL lines are high when the bus is idle. The appropriate method to go into the STOP condition is to ensure the
bus returns to idle state.
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START (S) and STOP (P) Conditions: To initiate communications, the master device transitions the SDA line
from high-to-low when the SCL is high. Conversely, to STOP the communication, the SDA goes low-to-high
when the SCL is high. To continue communication without termination of one transaction and beginning another,
a repeated START (Sr) method can be used without a STOP condition being initiated. These are the only
conditions (START or STOP) when SDA transitions when SCL is high.
Acknowledge Bits: An Acknowledge bit (A) is required after each data transfer byte to ensure correct
communications. This occurs when the receiving device pulls the SDA low before the rising edge of the
acknowledge-related clock pulse (ninth pulse) and keeps it low until the SCL returns low. There is also a
No-Acknowledge bit (N), which occurs when the receiver release the SDA line (high) before the rising edge of
acknowledge-related clock pulse, and maintains the SDA line high until SCL returns low. The Acknowledge bit
indicates if a successful data transfer has occurred between the master and slave device. Monitoring this bit also
indicates an unsuccessful data transfer due to the receiving device being busy or as system fault occurrence.
Communication Format
A START command immediately followed by a STOP command is an illegal format.
MSB
S
Slave Address
R/W
A
Data
A
P
S = START Command
R/W = Read from slave device ("1") or Write to slave device ("0")
A = Acknowledge bit
P = STOP Command
Slave Address = 7-bit address field for register address
DATA = 8-bit data field
PEC = Packet Error Checking
Slave to Master
Master to Slave
Communication Format for Multi-Word with Packet Error Checking (PEC)
Table 3. Write Byte with PEC
1
7
1
1
8
1
8
1
8
1
1
S
Slave Address
W
A
Command
Code
A
Data Byte
A
PEC
A
P
Table 4. Write Word with PEC
1
7
1
1
8
1
8
1
8
1
8
1
1
S
Slave
Address
W
A
Command
Code
A
Data Byte
Low
A
Data Byte
High
A
PEC
A
P
Table 5. Read Byte with PEC
1
7
1
1
8
1
1
7
1
1
8
1
8
1
1
S
Slave
Address
W
A
Command
Code
A
S
Slave
Address
R
A
Data Byte
A
PEC
A
P
Table 6. Read Word with PEC
1
7
1
1
8
1
1
7
1
1
8
1
8
1
8
1
1
S
Slave Address
W
A
Command
Code
A
S
Slave
Address
R
A
Data
Byte
Low
A
Data
Byte
High
A
PEC
A
P
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The communication format and protocol complies with SMBus.
GENERAL DESCRIPTION
The bq28550 accurately predicts the battery capacity and other operational characteristics of a single Li-Ion
based rechargeable cell, while it also provides a state-of-the-art protection function against short circuit,
overcurrent, and overvoltage. It can be integrated by a system processor to provide cell information, such as
state-of-charge (SOC), Remaining Capacity, and Full Charge Capacity (FCC).
NOTE
Formatting conventions in this document:
Commands: Italics with
RemainingCapacity().
parentheses
and
no
breaking
spaces;
for
example,
Data Flash: Italics, bold, and breaking spaces; for example, Design Capacity.
Register Bits and Flags: Brackets only; for example, [TDA]
Data Flash Bits: Italic and bold; for example, [NR]
Modes and States: All capitals; for example, SEALED mode.
DATA ACQUISITION
Cell Voltage
The bq28550 samples the single cell voltage from the BAT input terminal. The cell voltage is sampled and
updated every 1 s in normal mode. The VSS ground connection of the bq28550 should be connected to the
negative terminal of the sense resistor. This will prevent any error in short circuit and overcurrent measurements
across the external CHG and DSG FETs.
Charge Measurement
The device samples the charge into and out of the single cell using a low value sense resistor. The resistor
(typically 5 mΩ to 20 mΩ) is connected between SRP and SRN to form a differential input to an integrating ADC
(coulomb counter). Charge activity is detected when VSR = VSRP – VSRN is positive, and discharge activity is
detected when VSR = VSRP – VSRN is negative. This data is integrated over period of time, using an internal
counter and updates Remaining Capacity with charge and discharge amount every 1 s in normal mode.
Current Measurement
The device has a FIFO buffer, which uses the last four coulomb counter readings to calculate the current. The
current is updated every 1 s in normal mode.
TEMPERATURE MEASUREMENT AND THE TS INPUT
The bq28550 measures external temperature via the TS pin in order to supply battery temperature status
information to the gas gauging algorithm and charger-control sections of the gauge. Alternatively, the gauge can
also measure internal temperature via its on-chip temperature sensor. Refer to the Pack Configuration[TEMPS]
control bit.
Regardless of which sensor is used for measurement, a system processor can request the current battery
temperature by calling the Temperature( ) function (see STANDARD DATA COMMANDS for more information).
The temperature information is updated every 1 s in normal mode.
The bq28550 external temperature sensing is optimized with the use of a high accuracy negative temperature
coefficient (NTC) thermistor with R25 = 10 KΩ ± 1% and B25/85 = 3435 KΩ ± 1% (such as Semitec 103AT for
measurement). Additional circuit information for connecting this thermistor to the bq28550 is shown in
REFERENCE SCHEMATIC.
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OVER-TEMPERATURE INDICATION
Over-Temperature: Charge
If during charging Temperature() reaches the threshold of OT Chg for a period of OT Chg Time and
AverageCurrent() > Chg Current Threshold, then the [OC] bit is set based on the charge fault configuration
setting of CHG bit in the Control Status Register. When Temperature() falls to OT Chg Recovery, the [OC] bit is
reset.
If OT Chg Time = 0, the feature is completely disabled.
Over-Temperature: Discharge
If during discharging Temperature() reaches the threshold of OT Dsg for a period of OT Dsg Time, and
AverageCurrent() ≤ –Dsg Current Threshold, then the [DSGOFFREQ] bit is set. When Temperature() falls to
OT Dsg Recovery, the [DSGOFFREQ] bit is reset.
If OT Dsg Time = 0, the feature is completely disabled.
GAS GAUGING
Gas gauging information is accessed through a series of commands called Standard Commands. Further
capabilities are provided by the additional Extended Commands set. Both sets of commands, indicated by the
general format Command(), are used to read and write information contained within the bq28550 control and
status registers, as well as their data flash locations. Commands are sent from the system to the gauge using the
bq28550’s serial interface and can be executed during application development, pack manufacture, or
end-equipment operation.
Cell information is stored in the bq28550 non-volatile data flash memory. Many of these data flash locations are
accessible during application development. They cannot, generally, be accessed directly during end-equipment
operation. Access to these locations is achieved by either use of the bq28550 device’s companion evaluation
software, through individual commands, or through a sequence of data-flash-access commands. To access a
desired data flash location, the correct data flash subclass and offset must be known. The bq28550 provides 96
bytes of user-programmable data flash memory, partitioned into three, 32-byte blocks: Manufacturer Info Block
A, Manufacturer Info Block B, and Manufacturer Info Block C. For specifics on accessing the data flash, see
MANUFACTURER INFORMATION BLOCKS.
The bq28550 device’s gas gauging prediction uses a Compensated End of Discharge Voltage (CEDV) method.
This algorithm mathematically models the cell voltage as a function of the battery state-of-charge (SOC),
temperature, and current. The algorithm also models the battery impedance (Z) as a function of SOC and
temperature, with other parameters included in the calculation. The battery voltage model is used to calibrate full
charge capacity (FCC), and the compensated battery voltage can be used to indicate low battery voltage or
alarm function through firmware settings (Low Battery %, Fully Discharged).
The bq28550 measures discharge activity by monitoring the voltage across a small-value series sense resistor (5
mΩ to 20 mΩ typ) located between the CELL– and the battery’s PACKN terminal. This information is used to
integrate the battery discharge capacity and to estimate state of charge Q. This is then calculated as a
percentage of maximum capacity Qmax to indicate remaining state of charge SOC. The maximum capacity
parameter is updated on every full discharge cycle. There are other factors to be considered in estimating
remaining state of charge (RSOC), such as battery impedance, temperature, and aging due to number of
charge/discharge cycles. The equations used to determine the battery capacity factor these variables in to the
calculation based on battery chemistry.
PROTECTION
3.3.1 Overcharge Detector
When charging a battery, if the VBAT voltage becomes greater than the overcharge detection voltage
(VDET1 = 4.28 V typ) for a period up to the overcharge detection delay time (tDET1 = 1.00 s typ), the bq28550
detects the overcharge state of the battery, and the COUT pin transitions to a low level. This prohibits charging
the battery by turning off the external charge control N-channel MOSFET.
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In the overcharge state, if a charger is removed and a load is connected, the external charge control MOSFET
conducts the load current through its parasitic body diode. If the VBAT voltage becomes lower than the
overcharge release voltage (VREL1 = 4.1 V typ) for a period up to the overcharge release delay time
(tREL1 = 8 ms typ), the COUT pin transitions to a high level, enabling charge of the battery by turning on the
external charge control N-channel MOSFET.
3.3.2 Over-Discharge Detector
When discharging a battery, if the VBAT voltage becomes lower than the over-discharge detection voltage
(VDET2 = 2.3 V typ) for a period up to the over-discharge detection delay time (tDET2 = 24 ms typ), the bq28550
detects the over-discharge state of the battery, and the DOUT pin transitions to a low level. This prohibits
discharging the battery by turning off the external discharge control N-channel MOSFET.
In the over-discharge state, if a charger is connected, the external discharge control MOSFET conducts the
charge current through its parasitic body diode. If the VBAT voltage becomes greater than the over-discharge
detection voltage (VDET2 = 2.3 V typ) for a period up to the overcharge release delay time (tREL2 = 4 ms typ), the
DOUT pin transitions to a high level enabling discharge of the battery by turning on the external discharge control
N-channel MOSFET. After detecting over-discharge, the device stops all operations and enters standby, which
reduces the current consumed by the IC to its lowest mode (standby current).
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Over-Charge
Normal
Over-Discharge
ShutDown
Normal
Normal
BAT
VDET1
VREL1
DOUT
VDET2
BAT
COUT
VSS
BAT
VSS
VM
PACK -
BAT
VDET3
VSS
PACK -
tDET1
Charger
Connected
tDET2
tREL1
Load
Connected
tREL2
Charger
Connected
Discharge Overcurrent Detector and Short-Circuit Detector
If the voltage across both protection MOSFETs (VM – VSS) becomes higher than the discharge overcurrent
detection voltage (VDET3 = 0.150 V typ) for a period of up to the discharge overcurrent detection delay time
(tDET3 = 12 ms typ), the bq28550 detects the discharge overcurrent state of the battery and the DOUT pin
transitions to a low level. This prohibits discharging the battery by turning off the external discharge control
N-channel MOSFET.
Additionally, if the voltage across both protection MOSFETs (VM – VSS) becomes higher than the short-circuit
voltage (VSHORT = VBAT – 0.9 V typ) for a period of up to the discharge short-circuit detection delay time
(tSHORT = 400 µs typ), the bq28550 detects short-circuit of the battery and the DOUT pin transitions to a low level.
This prohibits discharging the battery by turning off the external discharge control N-channel MOSFET.
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In both the discharge overcurrent and short-circuit states, an internal discharge overcurrent release resistor (20
kΩ typ) is turned on (switched in between VM and VSS), allowing the VM pin to be pulled down to the VSS
potential if the load is released. If the VM – VSS voltage becomes lower than the discharge overcurrent detection
voltage (VDET3 = 0.150 V typ) for a period up to the discharge overcurrent release delay time (tREL3 = 4 ms typ),
the discharge overcurrent release resistor is turned off and the DOUT pin transitions to a high level, enabling
discharge of the battery by turning on the external discharge control N-channel MOSFET.
Discharge Over
Current
Normal
Discharge Over
Current
Normal
Normal
BAT
VDET1
VREL1
DOUT
VDET2
BAT
COUT
VSS
BAT
VSS
VM
PACK -
BAT
VSHORT
VDET3
VSS
tOCD
Load
Connected
14
tOCR
Load
Disconnected
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tSHORT
Load Short Circuit
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Charge Overcurrent Detector
If the voltage across both protection MOSFETs (VM – VSS) becomes more negative than the charge overcurrent
detection voltage (VDET4 = –0.112 V typ) for a period up to the charge overcurrent detection delay time
(tDET4 = 12 ms typ) due to an abnormal charging current or abnormal charging voltage, the bq28550 detects the
overcurrent charge state of the battery and the COUT pin transitions to a low level. This prohibits charging the
battery by turning off the external charge control N-channel MOSFET. The bq28550 releases from the charge
overcurrent detection state on by detecting the connection of a load for a period up to the overcharge release
delay time (tREL4 = 4 ms typ).
Table 7. Hardware Control Due to Fault Detection
Fault Condition
DOUT
COUT
Delay (typ)
Comment
Overcharge Voltage
Protection
ON
OFF
1s
Once OVP occurs for longer than the specified duration (1 s typ), the CHG FET
is turned OFF and bus communication is NOT valid. The system will support
power to the load with current flow through the CHG FET parasitic diode. This
can cause the cell to discharge; once the cell voltage reaches the overcharge
release voltage for the specified duration (8 ms typ), the CHG FET is turned ON
and bus communication is valid.
Overcurrent
Protection During
Charging
ON
OFF
12 ms
If the cell is being charged with excessive current, the threshold will be based
on a hardware limit measurement of –112 mV typ across the CHG + DSG FET
(VM – Vss) for a duration longer than 12 ms (typ), the CHG FET is turned OFF
and bus communication is not valid. This will prevent further charging of the cell.
The setting of the CHG bit in the control Status Register is dependent on the
OC bit setting in the Charge Fault Register selection. The FET bit in the Control
between the charger is removed and cell voltage falls below the threshold for
greater than 8 ms (typ). COUT is turned back ON. Once the host MCU takes
corrective action OR if the battery charger is removed AND there is a load
detected for a period of 4 ms (typ), the CHG FET is turned ON and bus
communication is valid.
Over Discharging
Voltage Protection
OFF
ON
24 ms
If the cell voltage falls to lower than 2.3 V for a duration of 24 ms (typ), the DSG
FET is turned OFF, bus communication is not valid. The system requires if
charger is connected and cell voltage rises above threshold for greater than 4
ms (typ), DOUT is turned back ON and bus communication is valid.
Overcurrent
Protection During
Discharging
OFF
ON
12 ms
If the cell is being discharged with excessive current, the threshold will be based
on a hardware limit measurement of 150 mV typ across the DSG + CHG FET
(VM – Vss) for a duration longer than 12 ms (typ) the DSG FET is turned OFF
and bus communication is NOT valid. This will prevent further discharging of the
cell, and the DSG bit in the control Status Register will be set. If the drop across
the DSG + CHG FET is less than the threshold OR there is no load detected for
a duration of 4 ms (typ), the DSG FET is turned ON and bus communication is
valid.
Short-Circuit
Protection
OFF
ON
400 µs
Detection of cell short circuit is measured at VM input. Shorted cell detection is
VBAT – 0.9 V for greater than 400 µs at VM terminal, and the DSG FET is turned
OFF and bus communication is NOT valid. The DSG bit in the control Status
Register will be set. The system will turn the DSG FET ON if the voltage at VM
is below 150 mV OR no load is detected.
Gas Gauge Control of Discharge DOUT Pin
Firmware Control of DOUT for Protection
The gas gauge firmware can override the hardware-based protection by forcing DOUT low to turn OFF the
discharge FET. However, the firmware cannot override the hardware protection to force discharge.
There are three conditions that enable firmware to force DOUT low:
1. The HOST_DISCONNECT (DSG FET OFF) subcommand—This feature is useful for the system to disable
the discharge FET from the battery pack if it fails to authenticate.
2. Pack removal detection by SDA and SCL pin falling low for more than 2 seconds—The DOUT pin override
condition is released upon detection of PACK insertion.
3. Firmware-based under voltage detection—The DOUT pin is forced low if voltage of the cell falls below the
Set Voltage threshold. The DOUT override condition is released when the voltage is above Clear Voltage.
Any one of the above three conditions will force the DOUT pin low. However, all three corresponding release
conditions must be satisfied before the DOUT override is returned to hardware-based protection control.
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Zero Voltage Charging
When the cell voltage is 0 V and if the charger voltage is above the minimum operating voltage for 0 V charging
(1.2-V max), the COUT output transitions to a high level and charge current can flow.
FET Control Protection
Figure 4 shows an overview of the FET Control Protection operation.
Shutdown
CHG: OFF
DSG: OFF
VREG: OFF
Attach a Charge
Short-Circuit
Protection
CHG: ON
DSG: OFF
VREG: ON
Over-Discharge
Protection
V- >VDD-0.9 V
for a period of t > 400 µs
V- < 0.15 V
or
No Load detected
Over-Current Protection
During Discharging
CHG: ON
DSG: OFF
VREG: ON
CHG: OFF
DSG: ON
VREG: ON
CHG: ON
DSG: OFF
VREG: OFF
Vcell > 2.3 V
for a period of
t > 4.0 ms
Vcell < 2.3 V
for a period of t > 24 ms
V- > 0.15 V for a period
of 12 ms
Normal
CHG: ON
DSG: ON
VREG: ON
V- < 0.15 V or
No Load detected
for a period of 4.0 ms
V- < – 0.112 V
for a period of 12 ms
Over-Current Protection
During Charging
No Charger
Charger removed and
Load detected
for a period of 4.0 ms
Vcell > 4.28 V
for a period
of 1.0 s
Vcell < 4.10 V
for a period of 8.0 ms
Over-Charge
Voltage Protection
CHG: OFF
DSG: ON
VREG: ON
Figure 4. FET Control Protection
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NOTE
When the CHG FET or DSG FET is turned OFF due to fault conditions, bus
communication is not valid. The bus communication will only be activated by removal of
the fault condition (see Table 7).
Regulator
Regulator out voltage is fixed at typically 2.5 V with a minimum output capacitance of 0.1 µF (0.47 µF typ). There
is an internal current limit designed for 60 mA (typ) when output is shorted to GND. When VDD is over 8.0 V
(typ), the regulator is turned off for the safety of the package dissipation.
DATA COMMANDS
STANDARD DATA COMMANDS
The bq28550 uses the following Command Code. Data RAM is updated and read by the gauge only once per
second. Standard commands are accessible in NORMAL operation mode.
Table 8. Standard Commands
Name
Command Code
Min Value
Max Value
Default value
Units
Sealed Access
ManufacturerAccess()
0x00
BatteryMode()
0x03
0x0000
0xffff
—
—
R/W
0x0000
0xe383
—
—
Temperature()
0x08
R/W
0
65535
—
0.1K
R
Voltage()
Current()
0x09
0
65535
—
mV
R
0x0a
–32768
32767
—
mA
AverageCurrent()
R
0x0b
–32768
32767
—
mA
R
R
MaxError()
0x0c
0
100
—
%
RelativeStateOfCharge()
0x0d
0
100
—
%
R
RemainingCapacity()
0x0f
0
65535
—
mAh or 10
mWh
R/W
FullChargeCapacity()
0x10
0
65535
7200
mA
R
ChargingCurrent()
0x14
0
65534
2500
mA
R
ChargingVoltage()
0x15
0
65534
12600
mV
R
BatteryStatus()
0x16
0x0000
0xdbff
—
—
R
CycleCount()
0x17
0
65535
0
—
R/W
DesignCapacity()
0x18
0
65535
7200
mAh
R/W
DesignVoltage()
0x18
0
65535
3600
mV
R/W
SpecificationInfo()
0x1a
0x0000
0xffff
0x0031
—
R/W
ManufactureDate()
0x1b
—
—
0
ASCII
R/W
SerialNumber()
0x1c
0x0000
0xffff
0x0001
—
R/W
ManufacturerName
0x20
—
—
Texas Inst
ASCII
R/W
DeviceName()
0x21
—
—
bq28550
ASCII
R/W
DeviceChemistry()
0x22
—
—
LION
ASCII
R/W
ManufactureData()
0x23
—
—
—
ASCII
R/W
Authenticate()
0x2f
—
—
—
ASCII
R
CellVoltage1()
0x3f
0
65535
—
mV
R
OperationStatus()
0x54
0x0000
0xffff
—
0xf7f7
R
ChargingStatus()
0x55
0x0000
0xffff
—
—
R
UnSealKey()
0x60
0x00000000
0xffffffff
—
—
R/W
Extended SBS Data Commands
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Table 8. Standard Commands (continued)
Name
Command Code
Min Value
Max Value
Default value
Units
Sealed Access
FullAccessKey()
0x61
0x00000000
0xffffffff
—
—
R/W
AuthenKey0()
0x63
0x00000000
0xffffffff
—
—
R/W
AuthenKey1()
0x64
0x00000000
0xffffffff
—
—
R/W
AuthenKey2()
0x65
0x00000000
0xffffffff
—
—
R/W
AuthenKey3()
0x66
0x00000000
0xffffffff
—
—
R/W
ManufacturerInfo()
0x70
—
—
—
ASCII
R/W
SenseResistor()
0x71
0
65535
—
µΩ
R/W
Temperature()
0x72
0x0000
0xffff
—
—
R
ManufacturerStatus()
0xB1
—
—
R
Run Time to Empty
Battery pack run time to empty can be calculated using the following method—the host system reads and stores
the following information during a discharge period and averages the data over a user-determined period of time:
• The DSG bit of the BatteryStatus register is set to ensure DOUT terminal is high (ensure the system is in
discharge mode).
• AverageCurrent (mA)
– Positive value = Charge Current
– Negative value = Discharge Current
– One minute rolling average of current value (the user can accumulate this time for improved granularity)
• RemainingCapacity (mAh)
Run Time To Empty = RemainingCapacity (avg mAh) ÷ AverageCurrent (mA). This result will be in hours, and
therefore to convert to minutes, divide the results by 60.
Charging Time To Full
This is a read only function that predicts the remaining time until battery reaches full charge in minutes based on
Average Current(). The computation accounts for the taper current time extension from the linear TTF
computation based on a fixed Average Current() rate of change of accumulation. A value of 65,535 indicates a
battery is NOT being charged.
Remaining Capacity Alert
To set a notification when battery capacity is below a pre-determined value, the user can set a Remaining
Capacity alarm alert in the system side. The Remaining Capacity value determined by the bq28550 is compared
to the user-selected value. If the Remaining Capacity value < the user-selected Remaining Capacity threshold,
the host system should instruct the user of what action is needed.
Remaining Time Alert
Similar to the Remaining Capacity notification, a system may require an alarm based on time rather than
Remaining Capacity. To set a notification when remaining time to empty is less than the user-set value, the user
can set a remaining time to empty alarm alert in the system side. The remaining time to empty value determined
by the bq28550 is compared to the user-selected value. If the Remaining Time to Empty value < the
user-selected Remaining Time to Empty threshold, the host system should instruct the user of what action to
take.
DATA FLASH INTERFACE
ACCESSING THE DATA FLASH
The bq28550 data flash is a non-volatile memory that contains bq28550 initialization, default, cell status,
calibration, configuration, and user information. The data flash can be accessed in several different ways,
depending on what mode the bq28550 is operating in and what data is being accessed.
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Commonly accessed data flash memory locations, frequently read by a system, are conveniently accessed
through specific instructions, as described in DATA COMMANDS. These commands are available when the
bq28550 is either in FULL ACCESS, UNSEALED, or SEALED modes.
Most data flash locations, however, are only accessible in FULL ACCESS or UNSEALED mode by using the
bq28550 evaluation software or by data flash block transfers. These locations should be optimized and/or fixed
during the development and manufacture processes. They become part of a golden image file and can then be
written to multiple battery packs. Once established, the values generally remain unchanged during
end-equipment operation.
READ-WRITE ACCESS OF DATA FLASH
To read and write commands in data flash, the following method is used:
Command Type
SBS Command
SBS Data
Description
Write Word
0x00
0x1yy
ManufacturerAccess() command to set up the data flash (DF)
address in order to write a row (32-byte) of data. Yy = the row
number where the target DF address is located.
Read/Write Block
0x2F
32-byte of data
ManufacturerInput() command. Issue this command after
setting up the DF address, to read/write the 32-byte data to
the DF.
The following is an example procedure to update a parameter in data flash.
1. Identify the physical byte location of the target parameter using the class and subclass ID information. This is
typically the subclass ID + Offset.
2. Identify the target row number by truncating the division of the byte location and the row length, e.g. a byte
location 27 would be in row: 27 divided by 32 = row number 0.
3. Byte location within the target row is determined by: Byte Index = physical location – (row number * row
length)
Byte
Index
=
27
–
(0
*32)
=
27
The target byte is in row 0 byte 27.
4. Using MAC command 0x1yy, where yy = row number. In this example, the SMBus write command would be
0x100.
5. Read the original target row first through a block read command 0x2F before updating.
6. Store original data in memory array, so the appropriate byte(s) can be updated.
SMBus block read cmd = 0x2F, length = 32 byte
7. Store the read data into a memory array (e.g yRowDataArray).
8. Update the target byte (yRowDataArray(27).
9. Write the updated yRowDataArray() array back to the device data flash. This done by repeating Step 4. Issue
SMBus block write cmd = 0 × 27, length 32.
10. A read verify is recommended to ensure the data flash has been re-programmed correctly. This is done by
repeating Steps 4 and 5 to do a read verify.
Flash Updates
Data flash can only be updated if Voltage() ≥ Flash Update OK Voltage. Flash programming current can cause
an increase in LDO dropout. The value of Flash Update OK Voltage should be selected such that the bq28550
VCC voltage does not fall below its minimum of 2.4 V during Flash write operations.
MANUFACTURER INFORMATION BLOCKS
The bq28550 contains 96 bytes of user-programmable data flash storage: Manufacturer Info Block A,
Manufacturer Info Block B, Manufacturer Info Block C. The method for accessing these memory locations is
slightly different, depending on whether the device is in FULL ACCESS, UNSEALED, or SEALED mode.
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ACCESS MODES
The bq28550 provides three security modes (FULL ACCESS, UNSEALED, and SEALED) that control data flash
access permissions according to the content in Table 9. Data flash refers to those data flash locations that are
accessible to the user, as specified in .
Table 9. Data Flash Access
Security Mode
SBS Commands
Data Flash
Device Programming
FULL ACCESS
Standard and Extended
Commands R/W
R/W
Yes
UNSEALED
Standard and some Extended
Commands R/W
R/W
No
SEALED
Standard Commands R/W
None
No
CHARGING AND CHARGE TERMINATION INDICATION
DETECTION CHARGE TERMINATION
For proper bq28550 operation, the cell charging voltage must be specified by the user. The default value for this
variable is in the data flash Charging Voltage.
The bq28550 detects charge termination when:
The battery current drops below the Taper Current for two consecutive Current Taper Window time periods
during charging AND battery voltage is equal to or higher than the Charging Voltage – Taper Voltage. Full
Charge is set when the taper condition is met.
CHARGE SUSPEND
The bq28550 suspends charging when: • Temperature < JT1, OR • Temperature > JT4 in charge-suspend mode,
if the [CHGSUSP] bit in OperationConfiguration is set. This will set the charging current to zero and the charging
voltage to zero in the Safety Status Register. Also, the CHG bit is reset in ControlStatus register. The bq28550
can indicate to resume charging if: • Temperature ≥ JT1 + Temp Hys, AND • Temperature ≤ JT3 – Temp Hys.
On resuming, the bq28550 sets the CHG bit in the ControlStatus Register, and sets ChargingCurrent according
to the appropriate charging mode entered. The bq28550 also leaves the charge-suspend mode when the battery
is removed in removable battery mode ([NR] = 0).
MANUFACTURER ACCESS(): 0x00/0x01
Issuing a Control() command requires a subsequent 2-byte subcommand. These additional bytes specify the
particular control function desired. The Control() command allows the system to control specific features of the
bq28550 during normal operation, and additional features when the device is in access modes (as described in
Table 10).
Table 10. Control() Subcommands
20
CNTL FUNCTION
CNTL DATA
SEALED ACCESS
DESCRIPTION
SET_FULLSLEEP
0x0010
Yes
Set the [FullSleep] bit in Control
Status register to 1
SET_HIBERNATE
0x0011
Yes
Forces CONTROL_STATUS
[HIBERNATE] to 1
CLEAR_HIBERNATE
0x0012
Yes
Forces CONTROL_STATUS
[HIBERNATE] to 0
SET_SHUTDOWN
0x0013
Yes
Forces CONTROL_STATUS
[SHUTDOWN] to 1
CLEAR_SHUTDOWN
0x0014
Yes
Forces CONTROL_STATUS
[SHUTDOWN] to 0
HOST_DISCONNECT
0x0017
Yes
Forces the DOUT pin low to
disable discharge.
HOST_Enable
0x0018
Yes
Forces the DOUT pin high to
enable discharge.
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Control Status: 0x0000
Instructs the gas gauge to return status information to Control Status 0x00/0x01. The status word should include
the following information.
Table 11. CONTROL STATUS Flags
Bit 7
Bit 6
Bit 5
Bit 4
Bit 3
Bit 2
Bit 1
Bit 0
High Byte
RSVD
RSVD
RSVD
RSVD
CCA
BCA
RSVD
RSVD
Low Byte
SHUTRQ
HIBERNATE
FULLSLEEP
SLEEP
DSGOFFREQ
RSVD
CHG
DSG
Low Byte
Bit 0 = DSG FET Status, 1 = Discharging allowed (DSG FET ON), 0 = Discharging NOT allowed ( DSG FET
Turned OFF)
Bit 1 = CHG FET Status, 1 = Charging allowed (CHG FET ON), 0 = Charging NOT allowed action to be taken by
Host MCU
Bit 2 = RSVD (Reserved)
Bit 3 = DSGOFFREQ, DSG FET OFF requested
Bit 4 = SLEEP, Status bit indicating the device is in SLEEP mode. True when set
Bit 5 = FULLSLEEP, Status bit indicating the device is in FULLSLEEP mode. True when set. The state can be
detected by monitoring the power used by the device because any communication will automatically clear it.
Bit 6 = HIBERNATE, Status bit indicating a request for entry into HIBERNATE from SLEEP mode has been
issued. True when set. Default is 0. Control bit when set will put the device into the lower power state of SLEEP
mode. It is not possible to monitor this bit Bit 7 = SHUTRQ, Status bit indicating the gas gauge is enabled to
enter SHUTDOWN mode. True when set. Default is 0.
Bit 7 = SHUTRQ, 1 = Shut down requested
High Byte
Bit 0, 1 = RSVD (Reserved)
Bit 2 = BCA = Status bit indicating the device Board Calibration routine is active. Active when set
Bit 3 = CCA = Status bit indicating the device Coulomb Counter Calibration routine is active. Active when set
Bit 4, 5, 6, 7 = RSVD (Reserved).
The following MAC commands are also available.
SET_FULLSLEEP: 0X0010
Instructs the gas gauge to set the FULLSLEEP bit in the Control Status register to 1. This allows the gauge to
enter the FULLSLEEP power mode after the transition to SLEEP power state is detected. In FULLSLEEP mode,
less power is consumed by disabling an oscillator circuit used by the communication engines. A communication
to the device in FULLSLEEP forces it back to SLEEP mode.
SET_HIBERNATE: 0x0011
Instructs the gas gauge to force the CONTROL_STATUS [HIBERNATE] bit to 1. This allows the gauge to enter
the HIBERNATE power mode after the transition to SLEEP power state is detected. The [HIBERNATE] bit is
automatically cleared upon exiting from HIBERNATE mode.
CLEAR_HIBERNATE: 0x0012
Instructs the gas gauge to force the CONTROL_STATUS [HIBERNATE] bit to 0. This prevents the gauge from
entering the HIBERNATE power mode after the transition to SLEEP power state is detected. It can also be used
to force the gauge out of HIBERNATE mode.
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SET_SHUTDOWN: 0x0013
Sets the CONTROL_STATUS [SHUTDOWN] bit to 1, enabling the device to enter SHUTDOWN mode if the
appropriate conditions are met.
CLEAR_SHUTDOWN: 0X0014
Clears the CONTROL_STATUS [SHUTDOWN] bit to 1, disabling the device from entering SHUTDOWN mode.
DSG FET OFF (HOST_DISCONNECT): 0x0017
Instructs the gas gauge to force the protection DOUT pin to low level. This prohibits discharging the battery by
turning off the external discharge control N-channel MOSFET.
DSG FET ON (HOST_CONNECT): 0x0018
Instructs the gas gauge to force the protection DOUT pin to high level. This allows discharging the battery by
turning on the external discharge control N-channel MOSFET.
POWER MODES
The bq28550 has four power modes: NORMAL, SLEEP, HIBERNATE, and SHUTDOWN. In NORMAL Mode, the
bq28550 is fully powered and can execute any allowable task. In SLEEP Mode, the gas gauge exists in a
reduced-power state, periodically taking measurements and performing calculations. In HIBERNATE Mode, the
gas gauge is in a low power state, but can be awaken by communication or certain I/O activity. The device
enters SHUTDOWN Mode if there is a UVP condition detected or power down of the system.
The relationship between these modes is shown in Figure 5. Details are described in the sections that follow.
POR
NORMAL
Entry to SHUTDOWN
Vcell < UVP and NO Charger
Present
Fuel gauging and data
updated every 1sec
Exit From HIBERNATE
V CELL < POR Threshold
Exit From HIBERNATE
Communication Activity
OR
bq28550clears Control Status
[HIBERNATE= 0]
Recommend Host also sets Control
Status [HIBERNATE] = 0
HIBERNATE
Disable all bq28550
.
subcircuits except GPIO
System HIBERNATION
Exit From SHUTDOWN
Charger Detected
AND
Protection FET’s ON
EXIT from SLEEP
Pack Configuaration[SLEEP] = 0
OR
AverageCurrent > Sleep Current
OR
Current is Detected aboveWAKE
I
Entry to SLEEP
Pack Configuaration[SLEEP] = 1
AND
AverageCurrent = Sleep Current
Wakeup From HIBERNATE
Communication Activity
AND
Comm address is NOT for bq
28550
SLEEP
Fuel gauging and data
updated every 20sec
SHUTDOWN
Entry to SHUTDOWN
Vcell < UVP and NO Charger
Present
Fuel Gauge is OFF,
VREG = 0V
Exit From WAIT_HIBERNATE
Host must set Control Status
[Hibernate= 0]
AND
V CELL > Hibernate Voltage
Exit From SLEEP
Host has set Control Status
[Hibernate= 1]
OR
VCELL < Hibernate Voltage
Entry to WAITFULLSLEEP
Full Sllep Wait Time> 0
Exit From WAITFULLSLEEP
Any Communication Cmd
System SHUTDOWN
WAITFULLSLEEP
FULLSLEEP Count Down
Entry to FULLSLEEP
Host must set Control Status
[FULLSLEEP= 1]
Entry to FULLSLEEP
Exit From FULLSLEEP
Count< 1
Any Communication Cmd
FULLSLEEP
Entry to SHUTDOWN
Vcell < UVP and NO Charger
Present
In low power state SLEEP
mode. Gas gauging and data
updated every20sec
System SLEEP
Figure 5. Power Mode Diagram
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NORMAL MODE
The gas gauge is in NORMAL Mode when not in any other power mode. During this mode, AverageCurrent(),
Voltage(), and Temperature() measurements are taken, and the interface data set is updated. Decisions to
change states are also made. This mode is exited by activating a different power mode.
Because the gauge consumes the most power in NORMAL Mode, the algorithm minimizes the time the gas
gauge remains in this mode.
SLEEP MODE
SLEEP Mode is entered automatically if the feature is enabled (Operation Configuration [SLEEP]) = 1) and
AverageCurrent() is below the programmable level Sleep Current. Once entry into SLEEP Mode has been
qualified, but prior to entering it, the bq28550 performs an ADC auto-calibration to minimize offset.
While in SLEEP Mode, the gas gauge can suspend serial communications as much as 4 ms by holding the
comm line(s) low. This delay is necessary to correctly process host communication, since the gas gauge
processor is mostly halted in SLEEP Mode.
During SLEEP Mode, the bq28550 periodically takes data measurements and updates its data set. However, a
majority of its time is spent in an idle condition. The bq28550 exits SLEEP if any entry condition is broken,
specifically when (1) AverageCurrent() rises above Sleep Current, or (2) a current in excess of IWAKE through
RSENSE is detected.
FULLSLEEP Mode
FULLSLEEP Mode is entered automatically if the feature is enabled by setting the Configuration [FULLSLEEP]
bit in the Control Status register when the bq28550 is in SLEEP Mode. The gauge exits FULLSLEEP Mode when
there is any communication activity. Therefore, the execution of SET_FULLSLEEP sets the [FULLSLEEP] bit,
but EVSW might still display the bit clear. FULLSLEEP Mode can be verified by measuring the current
consumption of the gauge. In this mode, the high frequency oscillator is turned off. The power consumption is
further reduced in this mode compared to the SLEEP Mode.
FULLSLEEP Mode can also be entered by setting the Full Sleep Wait Time to be a number larger than 0.
FULLSLEEP will be entered when the timer counts down to 0. This feature is disabled when the data flash is set
as 0.
During FULLSLEEP Mode, the bq28550 periodically takes data measurements and updates its data set.
However, a majority of its time is spent in an idle condition.
The bq28550 exits SLEEP if any entry condition is broken, specifically when (1) AverageCurrent() rises above
Sleep Current, or (2) a current in excess of IWAKE through RSENSE is detected.
While in FULLSLEEP Mode, the gas gauge can suspend serial communications as much as 4 ms by holding the
comm line(s) low. This delay is necessary to correctly process host communication, since the gas gauge
processor is mostly halted in SLEEP Mode.
HIBERNATE MODE
HIBERNATE Mode should be used when the host system needs to enter a low-power state, and minimal gauge
power consumption is required. This mode is ideal when the host is set to its own HIBERNATE, SHUTDOWN, or
OFF modes. The gas gauge can enter HIBERNATE due to either low cell voltage or low load current.
• HIBERNATE due to the load current—If the gas gauge enters HIBERNATE Mode due to the load current, the
[HIBERNATE] bit of the CONTROL_STATUS register must be set. The gauge waits to enter HIBERNATE
Mode until it has taken a valid OCV measurement and the magnitude of the average cell current has fallen
below Hibernate Current.
• HIBERNATE due to the cell voltage—When the cell voltage drops below the Hibernate Voltage and a valid
OCV measurement has been taken, the gas gauge enters HIBERNATE Mode. The [HIBERNATE] bit of the
CONTROL register has no impact for the gas gauge to enter the HIBERNATE Mode. If the [SHUTDOWN] bit
of CONTROL _STATUS is also set.
The gauge will remain in HIBERNATE Mode until communication activity appears on the communication lines.
Upon exiting HIBERNATE Mode, the [HIBERNATE] bit of CONTROL_STATUS is cleared.
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Because the gas gauge is dormant in HIBERNATE Mode, the battery should not be charged or discharged in this
mode, because any changes in battery charge status will not be measured. If necessary, the host equipment can
draw a small current (generally infrequent and less than 1 mA, for purposes of low-level monitoring and
updating); however, the corresponding charge drawn from the battery will not be logged by the gauge. Once the
gauge exits to NORMAL Mode, the algorithm re-establishes the correct battery capacity.
If a charger is attached, the host should immediately take the gas gauge out of HIBERNATE Mode before
beginning to charge the battery.
CAUTION
Charging the battery in HIBERNATE Mode results in a notable gauging error that will
take several hours to correct.
SHUTDOWN MODE
The device enters SHUTDOWN Mode if there is a UVP condition detected or power down of the system, and
alternatively by setting the SHUTRQ bit to 1, if appropriate conditions are met. The device can also disable
SHUTDOWN by using the CLEAR_SHUTDOWN (0x0014) option.
Figure 6 shows an overview of the hardware controlled SHUTDOWN operation.
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Shutdown
CHG: OFF
DSG: OFF
VREG: OFF
No Charger
Charger attached
Over-Discharge
Voltage
CHG: ON
DSG: OFF
VREG OFF
Vcell < 2.3 V
for a period
of t > 24 ms
Vcell > 2.3 V
for a period
of t > 4.0 ms
Normal
CHG: ON
DSG: ON
VREG: ON
FG shutdown
Vcell < 2.3 V
for a period
of t > 24 ms
FG turn
on DSG
FG turn
off DSG
DSG “OFF”
CHG: ON
DSG: OFF
VREG: ON
Figure 6. Shutdown Operation
OPERATIONAL MODES
The mode of going from one state to another is as follows, NORMAL → SLEEP → FULLSLEEP; then from
FULLSLEEP either HIBERNATE or SHUTDOWN.
Mode
NORMAL
Enter Mode
Exit Mode
If ALL conditions are satisfied like
Average Current, Cell Voltage, and
Temperature
Go into other modes like SLEEP,
FULLSLEEP, HIBERNATE, or
SHUTDOWN mode if conditions are
satisfied
Comment
In this mode, power consumption is
the highest. Measurements are taken
and updated every 1 s.
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Mode
SLEEP
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Enter Mode
Exit Mode
Comment
SLEEP bit set = 1 in operation
register AND AverageCurrent
measured is equal to Sleep current
value.
Change SLEEP bit = 0 OR
The data is measured every 20 s to
AverageCurrent measurement > Sleep reduce current consumption.
current value OR Current detected is
above the IWAKE setting.
From SLEEP mode if the
WAIT_FULLSLEEP wait is
programmed, this is the time the
system must be in SLEEP mode
before it can go to FULLSLEEP
mode.
The system exits the FULLSLEEP
mode if there are any communication
commands set on the bus to the
device.
The wait time to enter FULLSLEEP
from SLEEP is 1 s to 240 s with the
default at 15 s.
HIBERNATION
From FULL SLEEP mode, the
system will go into HIBERNATE
mode if the load current decreases to
programmed value
OR if the cell voltage falls below
programmed value
OR the host sets the command in
MAC.
The system exits this mode is the
VCELL > programmed threshold
OR load current is > programmed
threshold
OR communication activity on bus line
OR host sets the command in MAC.
Enters hibernation if VCELL range is
2.4 V to 3 V with default at 2.55 V.
The load current threshold range is 0
to 0.7 A with a default value of 8 mA.
SHUTDOWN
From SLEEP mode, the system will
enter this mode if the VCELL < 2.4 V
for a period longer than 24 ms and
the charger is not attached. The
system can also be put in
SHUTDOWN mode through MAC.
Exit from this mode if there is bus
activity
OR the load current detected is >
IWAKE
OR charger is connected to the
system.
In this mode, the VREG and DSG
FET are turned OFF and the system
will only wake up if the charger is
attached on the Pack+, Pack–
terminals.
FULLSLEEP
AUTO-CALIBRATION
The bq28550 provides an auto-calibration feature that measures the voltage offset error across SRP and SRN
from time-to-time as operating conditions change. It subtracts the resulting offset error from the normal sense
resistor voltage, VSR, for maximum measurement accuracy.
Auto-calibration of the ADC begins on entry to SLEEP mode, except if Temperature() is ≤ 5°C or Temperature()
≥ 45°C.
The gas gauge also performs a single offset when (1) the condition of AverageCurrent() ≤ 100 mA and (2) {cell
voltage change since last offset calibration ≥ 256 mV} or {temperature change since last offset calibration is
greater than 80°C for ≥ 60 s}.
Capacity and current measurements continue at the last measured rate during the offset calibration when these
measurements cannot be performed. If the battery voltage drops more than 32 mV during the offset calibration,
the load current has likely increased considerably and the offset calibration will be aborted.
COMMUNICATIONS
AUTHENTICATION
The bq28550 can act as a SHA-1/HMAC authentication slave by using its internal engine. Refer to the
Application Note SLUA359 for SHA-1/HMAC for information.
By sending a 160-bit SHA-1 challenge message to the bq28550, it causes the gauge to return a 160-bit digest,
based upon the challenge message and a hidden, 128-bit plain-text authentication key. If this digest matches an
identical one generated by a host or dedicated authentication master, and when operating on the same challenge
message and using the same plain text keys, the authentication process is successful.
Key Programming (Data Flash Key)
By
default,
the
bq28550
contains
a
default
plain-text
authentication
key
of
0x0123456789ABCDEFFEDCBA9876543210. This default key is intended for development purposes. It should
be changed to a secret key and the part immediately sealed before putting a pack into operation. Once written, a
new plain-text key cannot be read again from the gas gauge while in SEALED mode.
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Once the bq28550 is FULL ACCESS, the authentication key can be changed from its default value by writing to
the Authentication() Extended Data Command locations. A 0x00 is written to BlockDataControl() to enable the
authentication data commands. The bq28550 is now prepared to receive the 16-byte plain-text key, which must
begin at the command location 0x40 and ending at 0x4f. Once written, the key is accepted when a successful
checksum for the key has been written to AuthenticateChecksum(). The gauge can then be SEALED again.
Key Programming (The Secure Memory Key)
As the name suggests, the bq28550 secure-memory authentication key is stored in the secure memory of the
bq28550.
If
a
secure-memory
key
has
been
established
and
Data
Flash
Key
is
0x00000000000000000000000000000000, only this key can be used for authentication challenges (the
programmable data flash key is not available). The selected key can only be established/programmed by special
arrangements with TI, using TI’s Secure B-to-B Protocol. The secure-memory key can never be changed or read
from the bq28550.
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TP2
TP1
CELL–
CELL–
CELL+
TB1
3
R1
0.005
100
C1
R2
100
0.1µF
C2
0.1µF
R4
3.01M
Q1-A
SI6928DQ
Q1-B
SI6928DQ
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R13
C3
1K
WAKE
0.1µF
S1
C4
0.1µF
R5
3.01M
0.1µF
R6
510
TP6
VM
1uF
6 VSS
4 BAT
3 VM
5 VREG
C6
1 DOUT
2 COUT
1
C5
0.47µF
RT1
10K
SRP 7
SRN 8
TS 9
SDA 10
SCL 11
HDQ 12
U1
BQ28550DRZ
C7
2
R3
TP7 DOUT
TP5 COUT
VREG
13 PWPD
28
CELL+
TP8
J2
0.1µF
C8
2
2
R8
3.3K
1
J3
1
R9 100
R7
3.3K
J4
1
R14
3.3K
D2
100 R12 100
MM3Z5V6C
D1
R11
R10 100
2
4
1
2
3
J1
SDA
GND
SCL
TP4
PACK–/LOAD–
PACK+/LOAD+
TB2
TP3
PACK–
1
2
3
PACK+
bq28550
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REFERENCE SCHEMATIC
SCHEMATIC
Copyright © 2011, Texas Instruments Incorporated
PACKAGE OPTION ADDENDUM
www.ti.com
20-Feb-2012
PACKAGING INFORMATION
Orderable Device
Status
(1)
Package Type Package
Drawing
Pins
Package Qty
Eco Plan
(2)
Lead/
Ball Finish
MSL Peak Temp
(3)
BQ28550DRZR
ACTIVE
SON
DRZ
12
3000
Green (RoHS
& no Sb/Br)
CU NIPDAU Level-2-260C-1 YEAR
BQ28550DRZT
ACTIVE
SON
DRZ
12
250
Green (RoHS
& no Sb/Br)
CU NIPDAU Level-2-260C-1 YEAR
Samples
(Requires Login)
(1)
The marketing status values are defined as follows:
ACTIVE: Product device recommended for new designs.
LIFEBUY: TI has announced that the device will be discontinued, and a lifetime-buy period is in effect.
NRND: Not recommended for new designs. Device is in production to support existing customers, but TI does not recommend using this part in a new design.
PREVIEW: Device has been announced but is not in production. Samples may or may not be available.
OBSOLETE: TI has discontinued the production of the device.
(2)
Eco Plan - The planned eco-friendly classification: Pb-Free (RoHS), Pb-Free (RoHS Exempt), or Green (RoHS & no Sb/Br) - please check http://www.ti.com/productcontent for the latest availability
information and additional product content details.
TBD: The Pb-Free/Green conversion plan has not been defined.
Pb-Free (RoHS): TI's terms "Lead-Free" or "Pb-Free" mean semiconductor products that are compatible with the current RoHS requirements for all 6 substances, including the requirement that
lead not exceed 0.1% by weight in homogeneous materials. Where designed to be soldered at high temperatures, TI Pb-Free products are suitable for use in specified lead-free processes.
Pb-Free (RoHS Exempt): This component has a RoHS exemption for either 1) lead-based flip-chip solder bumps used between the die and package, or 2) lead-based die adhesive used between
the die and leadframe. The component is otherwise considered Pb-Free (RoHS compatible) as defined above.
Green (RoHS & no Sb/Br): TI defines "Green" to mean Pb-Free (RoHS compatible), and free of Bromine (Br) and Antimony (Sb) based flame retardants (Br or Sb do not exceed 0.1% by weight
in homogeneous material)
(3)
MSL, Peak Temp. -- The Moisture Sensitivity Level rating according to the JEDEC industry standard classifications, and peak solder temperature.
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Addendum-Page 1
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