BQ27546-G1 Datasheet, PDF (14/38 Pages) Texas Instruments – nullSingle-Cell Li-Ion Battery Fuel Gauge

bq27546-G1
SLUSC53A – MAY 2015 – REVISED DECEMBER 2015
Attempt to write a read-only address (NACK after data sent by master):
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S ADDR[6:0] 0 A CMD[7:0]
A DATA[7:0]
AP
Attempt to read an address above 0x7F (NACK command):
S
ADDR[6:0]
0 A CMD[7:0] N P
Attempt at incremental writes (NACK all extra data bytes sent):
S ADDR[6:0] 0 A CMD[7:0] A DATA[7:0]
A DATA[7:0] N _{. . .} N P
Incremental read at the maximum allowed read address:
S ADDR[6:0] 0 A CMD[7:0]
A Sr ADDR[6:0] 1 A DATA[7:0]
A . . . DATA[7:0] N P
Address
0x7F
Data From
addr 0x7F
Data From
addr 0x00
The I²C engine releases both SDA and SCL if the I²C bus is held low for t_(BUSERR). If the fuel gauge was holding
the lines, releasing them frees the master to drive the lines. If an external condition is holding either of the lines
low, the I²C engine enters the low-power SLEEP mode.
9.3.5.7.1 I²C Time Out
The I²C engine will release both SDA and SCL if the I²C bus is held low for about 2 seconds. If the bq27546-G1
device were holding the lines, releasing them frees for the master to drive the lines.
9.3.5.7.2 I²C Command Waiting Time
To ensure there are correct results of a command with the 400-KHz I²C operation, a proper waiting time should
be added between issuing command and reading results. For subcommands, the following diagram shows the
waiting time required between issuing the control command the reading the status with the exception of the
checksum command. A 100-ms waiting time is required between the checksum command and reading result. For
read-write standard commands, a minimum of 2 seconds is required to get the result updated. For read-only
standard commands, there is no waiting time required, but the host should not issue all standard commands
more than two times per second. Otherwise, the gauge could result in a reset issue due to the expiration of the
watchdog timer.
S ADDR[6:0] 0 A
S ADDR[6:0] 0 A
CMD[7:0]
CMD[7:0]
A DATA [7:0] A DATA [7:0] A P 66ms
A Sr ADDR[6:0] 1 A DATA [7:0] A DATA [7:0]
Waiting time between control subcommand and reading results
N P 66ms
S ADDR[6:0] 0 A CMD[7:0] A Sr ADDR[6:0] 1 A DATA [7:0] A DATA [7:0] A
DATA [7:0] A DATA [7:0] N P 66ms
Waiting time between continuous reading results
Figure 8. I²C Command Waiting Time
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