Datasheet

t
SU(STA)
SCL
SDA
t
w(H)
t
w(L)
t
f
t
r
t
(BUF)
t
r
t
d(STA)
REPEATED
START
t
h(DAT)
t
su(DAT)
t
f
t
su(STOP)
STOP START
bq27541-G1
www.ti.com SLUSAL6C –NOVEMBER 2011–REVISED OCTOBER 2012
I
2
C-COMPATIBLE INTERFACE TIMING CHARACTERISTICS
T
A
= –40°C to 85°C, C
REG
= 0.47μF, 2.45 V < V
REGIN
= V
BAT
< 5.5 V; typical values at T
A
= 25°C and V
REGIN
= V
BAT
= 3.6 V
(unless otherwise noted)
PARAMETER TEST CONDITIONS MIN TYP MAX UNIT
t
r
SCL/SDA rise time 300 ns
t
f
SCL/SDA fall time 300 ns
t
w(H)
SCL pulse width (high) 600 ns
t
w(L)
SCL pulse width (low) 1.3 μs
t
su(STA)
Setup for repeated start 600 ns
t
d(STA)
Start to first falling edge of SCL 600 ns
t
su(DAT)
Data setup time 1000 ns
t
h(DAT)
Data hold time 0 ns
t
su(STOP)
Setup time for stop 600 ns
t
BUF
Bus free time between stop and start 66 μs
f
SCL
Clock frequency 400 kHz
Figure 2. I
2
C-Compatible Interface Timing Diagrams
GENERAL DESCRIPTION
The bq27541-G1 accurately predicts the battery capacity and other operational characteristics of a single Li-
based rechargeable cell. It can be interrogated by a system processor to provide cell information, such as state-
of-charge (SOC) and time-to-empty (TTE).
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 bq27541-G1 control and status
registers, as well as its data flash locations. Commands are sent from system to gauge using the bq27541-G1
serial communications engine, and can be executed during application development, pack manufacture, or end-
equipment operation.
Cell information is stored in the bq27541-G1 in non-volatile 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 bq27541-G1 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 bq27541-G1 provides 64 bytes of user-programmable data flash memory, partitioned into two (2) 32-byte
blocks: Manufacturer Info Block A and Manufacturer Info Block B. This data space is accessed through a
data flash interface. For specifics on accessing the data flash, see section Manufacturer Information Blocks. The
key to the bq27541-G1 high-accuracy gas gauging prediction is Texas Instrument’s proprietary Impedance
Track™ algorithm. This algorithm uses cell measurements, characteristics, and properties to create state-of-
charge predictions that can achieve less than 1% error across a wide variety of operating conditions and over the
lifetime of the battery.
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