BQ25700A Datasheet, PDF (48/82 Pages) Texas Instruments – SMBus Multi-Chemistry Battery Buck-Boost Charge Controller With System Power Monitor and Processor Hot Monitor

bq25700A
SLUSCQ8 – MAY 2017
www.ti.com
8.6.3 ChargeCurrent Register (SMBus address = 14h) [reset = 0h]
To set the charge current, write a 16-bit ChargeCurrent() command (REG0x14()) using the data format listed in
Table 25 and Table 26.
With 10-mΩ sense resistor, the charger provides charge current range of 64 mA to 8.128 A, with a 64-mA step
resolution. Upon POR, ChargeCurrent() is 0 A. Any conditions for CHRG_OK low except ACOV will reset
ChargeCurrent() to zero. CELL_BATPRESZ going LOW (battery removal) will reset the ChargeCurrent() register
to 0 A.
Charge current is not reset in ACOC, TSHUT, power path latch off (REG0x30[1]), and SYSOVP.
A 0.1-µF capacitor between SRP and SRN for differential mode filtering is recommended; an optional 0.1-µF
capacitor between SRN and ground, and an optional 0.1-µF capacitor between SRP and ground for common
mode filtering. Meanwhile, the capacitance on SRP should not be higher than 0.1 µF in order to properly sense
the voltage across SRP and SRN for cycle-by-cycle current detection.
The SRP and SRN pins are used to sense voltage drop across RSR with default value of 10 mΩ. However,
resistors of other values can also be used. For a larger sense resistor, a larger sense voltage is given, and a
higher regulation accuracy; but, at the expense of higher conduction loss. If current sensing resistor value is too
high, it may trigger an over current protection threshold because the current ripple voltage is too high. In such a
case, either a higher inductance value or a lower current sensing resistor value should be used to limit the
current ripple voltage level. A current sensing resistor value no more than 20 mΩ is suggested.
Figure 26. ChargeCurrent Register With 10-mΩ Sense Resistor (SMBus address = 14h) [reset = 0h]
15
14
13
12
11
10
9
8
Reserved
Charge
Current, bit 6
Charge
Current, bit 5
Charge
Current, bit 4
Charge
Current, bit 3
Charge
Current, bit 2
R/W
R/W
R/W
R/W
R/W
R/W
7
6
5
4
3
2
1
0
Charge
Current, bit 1
Charge
Current, bit 0
Reserved
Reserved
R/W
R/W
R/W
R/W
LEGEND: R/W = Read/Write; R = Read only; -n = value after reset
Table 25. Charge Current Register (14h) With 10-mΩ Sense Resistor (SMBus address = 14h) Field
Descriptions
SMBus
BIT
FIELD
TYPE
RESET DESCRIPTION
15-13 Reserved
R/W
000b
Not used. 1 = invalid write.
12 Charge Current, bit 6
R/W
0b
0 = Adds 0 mA of charger current.
1 = Adds 4096 mA of charger current.
11 Charge Current, bit 5
R/W
0b
0 = Adds 0 mA of charger current.
1 = Adds 2048 mA of charger current.
10 Charge Current, bit 4
R/W
0b
0 = Adds 0 mA of charger current.
1 = Adds 1024 mA of charger current.
9
Charge Current, bit 3
R/W
0b
0 = Adds 0 mA of charger current.
1 = Adds 512 mA of charger current.
8
Charge Current, bit 2
R/W
0b
0 = Adds 0 mA of charger current.
1 = Adds 256 mA of charger current.
Table 26. Charge Current Register (14h) With 10-mΩ Sense Resistor (SMBus address = 14h) Field
Descriptions
SMBus
BIT
7
FIELD
Charge Current, bit 1
TYPE
R/W
RESET
0b
DESCRIPTION
0 = Adds 0 mA of charger current.
1 = Adds 128 mA of charger current.
48
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