BQ27425-G2_15 Datasheet, PDF (27/39 Pages) Texas Instruments – Fuel Gauge With Integrated Sense Resistor

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bq27425-G2
SLUSB23B – OCTOBER 2012 – REVISED JUNE 2015
8.5.7.4 I²C Clock Stretching
A clock stretch can occur during all modes of fuel gauge operation. In SLEEP and HIBERNATE modes, a short
clock stretch occurs on all I²C traffic as the device must wake up to process the packet. In the other modes
(INITIALIZATION, NORMAL) clock stretching only occurs for packets addressed for the fuel gauge. The majority
of clock stretch periods are small as the I²C interface performs normal data flow control. However, less frequent
yet more significant clock stretch periods may occur as blocks of NVM are updated. The following table
summarizes the approximate clock stretch duration for various fuel gauge operating conditions.
Table 10. I²C Clock Stretching
GAUGING
MODE
SLEEP
HIBERNATE
INITIALIZATION
NORMAL
OPERATING CONDITION / COMMENT
Clock stretch occurs at the beginning of all traffic as the device wakes up.
Clock stretch occurs within the packet for flow control (after a start bit, ACK or first data bit).
Normal Ra table NVM updates.
NVM block writes.
Restored NVM block write after loss of power.
End of discharge Ra table NVM update.
APPROXIMATE
DURATION
≤ 4 ms
≤ 4 ms
24 ms
72 ms
116 ms
144 ms
8.6 Register Maps
8.6.1 Operation Configuration (Op Config) Register
Gauge operation is configured through the Operation Configuration (Op Config) data NVM register, as
indicated in Table 11. This register is programmed and read through the methods described in Fuel Gauging
Configurations.
BIT 7
High Byte SMOOTHEN
Default =
1
Low Byte
Default =
RSVD1
1
Table 11. Op Config Register Definition
BIT 6
RSVD0
0
RSVD1
1
BIT 5
BIE
0
SLEEP
1
BIT 4
BIT 3
BI_PU_EN
RSVD1
0
1
0x89
RMFCC
RSVD1
1
1
0xF8
BIT 2
RSVD0
0
BATLOWEN
0
BIT 1
RSVD0
0
GPIOPOL
0
BIT 0
RSVD1
1
TEMPS
0
SMOOTHEN = Enables the SOC smoothing feature. (See SOC Smoothing Feature.) True when set.
BIE = Battery Insertion Enable. If set, the battery insertion is detection through BIN pin input. If cleared, the detection
relies on the host to issue BAT_INSERT subcommand to indicate battery presence in the system.
BI_PU_EN = Enables internal weak pullup on BIN pin. True when set. If false, an external pullup resistor is expected.
SLEEP = The fuel gauge can enter sleep, if operating conditions allow. True when set.
RMFCC = RM is updated with the value from FCC on valid charge termination. True when set.
BATLOWEN = If set, the BAT_LOW function for GPOUT pin is selected. If cleared, the SOC_INT function is selected for
GPOUT.
GPIO_POL = GPOUT pin is active-HIGH if set or active-LOW if cleared.
TEMPS = Selects the temperature source. Enables the host to write Temperature( ) if set. If cleared, the internal
temperature sensor is used for Temperature( ).
RSVD0 = Reserved. Default is 0. (Set to 0 for proper operation)
RSVD1 = Reserved. Default is 1. (Set to 1 for proper operation)
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