BQ27425-G2_15 Datasheet, PDF (25/39 Pages) Texas Instruments – Fuel Gauge With Integrated Sense Resistor

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bq27425-G2
SLUSB23B – OCTOBER 2012 – REVISED JUNE 2015
CLASS
Security
Table 9. Data Block Summary (continued)
SUBCLASS
ID
SUBCLASS
OFFSET
NAME
DATA
TYPE
112
Codes [RAM]
0
Sealed to Unsealed
H4
MIN
0x0000
0000
VALUE
MAX
0xFFFF
FFFF
DEFAULT
(-G2B)
0x3672
0414
UNIT
(EVSW
Unit)*
8.5.6 Detecting Charge Termination
The fuel gauge detects charge termination when:
• AverageCurrent( ) < Taper Current (default = 75 mA) for 80 seconds
• During the same 80 seconds, the accumulated change in capacity > 0.25 mAh / 40 seconds
• Voltage( ) > (Charging Voltage – 100 mV)
When this occurs, the Flags( )[CHG] bit is cleared. Also, if the [RMFCC] bit of Operation Configuration is set,
then RemainingCapacity( ) is set equal to FullChargeCapacity( ).
8.5.7 Communications
8.5.7.1 I²C Interface
The fuel gauge supports the standard I²C read, incremental read, quick read, one-byte write, and incremental
write functions. The 7-bit device address (ADDR) is the most significant 7 bits of the hex address and is fixed as
1010101. The first 8 bits of the I²C protocol are, therefore, 0xAA or 0xAB for write or read, respectively.
Host generated
Gauge generated
S ADDR[6:0] 0 A CMD [7:0] A DATA [7:0] A P
S ADDR[6:0] 1 A DATA [7:0]
(a) 1-byte write
(b) quick read
S ADDR[6:0] 0 A CMD [7:0] A Sr ADDR[6:0] 1 A DATA [7:0] N P
(c) 1- byte read
NP
S ADDR[6:0] 0 A
CMD [7:0]
A Sr ADDR[6:0] 1 A
(d) incremental read
DATA [7:0]
A ...
DATA [7:0]
NP
S ADDR[6:0] 0 A CMD[7:0] A DATA [7:0] A DATA [7:0]
(e) incremental write
(S = Start , Sr = Repeated Start , A = Acknowledge , N = No Acknowledge , and P = Stop).
Figure 7. I²C Interface Read/Write
A ... A P
The quick read returns data at the address indicated by the address pointer. The address pointer, a register
internal to the I²C communication engine, increments whenever data is acknowledged by the fuel gauge or the
I²C master. “Quick writes” function in the same manner and are a convenient means of sending multiple bytes to
consecutive command locations (such as two-byte commands that require two bytes of data).
The following command sequences are not supported:
Attempt to write a read-only address (NACK after data sent by master):
Figure 8. Attempt to Write a Read-Only Address
Attempt to read an address above 0x6B (NACK command):
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