BQ25703A Datasheet, PDF (54/81 Pages) Texas Instruments – I2C Multi-Chemistry Battery Buck-Boost Charge Controller With System Power Monitor and Processor Hot Monitor

bq25703A
SLUSCU1 – MAY 2017
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8.6.5 MinSystemVoltage Register (I2C address = 0D/0Ch) [reset value based on CELL_BATPRESZ pin
setting]
To set the minimum system voltage, write a 16-bit MinSystemVoltage register command (REG0x0D/0C()) using
the data format listed in Table 27 and Table 28. The charger provides minimum system voltage range from 1.024
V to 16.128 V, with 256-mV step resolution. Any write below 1.024 V or above 16.128 V is ignored. Upon POR,
the MinSystemVoltage register is 3.584 V for 1 S, 6.144 V for 2 S and 9.216 V for 3 S, and 12.288 V for 4 S.
Figure 34. MinSystemVoltage Register (I2C address = 0D/0Ch) [reset value based on CELL_BATPRESZ
pin setting]
15
14
Reserved
R/W
13
Min System
Voltage, bit 5
R/W
12
Min System
Voltage, bit 4
R/W
11
Min System
Voltage, bit 3
R/W
10
Min System
Voltage, bit 2
R/W
9
Min System
Voltage, bit 1
R/W
7
6
5
4
3
2
1
Reserved
R/W
LEGEND: R/W = Read/Write; R = Read only; -n = value after reset
Table 27. MinSystemVoltage Register (I2C address = 0Dh) Field Descriptions
I2C
0Dh
FIELD
TYPE
RESET DESCRIPTION
7-6 Reserved
R/W
00b
Not used. 1 = invalid write.
5
Min System Voltage, bit 5
R/W
0b
0 = Adds 0 mV of system voltage.
1 = Adds 8192 mV of system voltage.
4
Min System Voltage, bit 4
R/W
0b
0 = Adds 0 mV of system voltage.
1 = Adds 4096mV of system voltage.
3
Min System Voltage, bit 3
R/W
0b
0 = Adds 0 mV of system voltage.
1 = Adds 2048 mV of system voltage.
2
Min System Voltage, bit 2
R/W
0b
0 = Adds 0 mV of system voltage.
1 = Adds 1024 mV of system voltage.
1
Min System Voltage, bit 1
R/W
0b
0 = Adds 0 mV of system voltage.
1 = Adds 512 mV of system voltage.
0
Min System Voltage, bit 0
R/W
0b
0 = Adds 0 mV of system voltage.
1 = Adds 256 mV of system voltage.
Table 28. MinSystemVoltage Register (I2C address = 0Ch) Field Descriptions
I2C
0Ch
FIELD
7-0 Reserved
TYPE
R/W
RESET DESCRIPTION
0000000 _{Not used. Value Ignored.}
0b
8
Min System
Voltage, bit 0
R/W
0
8.6.5.1 System Voltage Regulation
The device employs Narrow VDC architecture (NVDC) with BATFET separating system from battery. The
minimum system voltage is set by REG0x0D/0C(). Even with a deeply depleted battery, the system is regulated
above the minimum system voltage with BATFET.
When the battery is below minimum system voltage setting, the BATFET operates in linear mode (LDO mode),
and the system is regulated above the minimum system voltage setting. As the battery voltage rises above the
minimum system voltage, BATFET is fully on when charging or in supplement mode and the voltage difference
between the system and battery is the VDS of BATFET. System voltage is regulated 160 mV above battery
voltage when BATFET is off (no charging or no supplement current).
When BATFET is removed, the system node VSYS is shorted to SRP. Before the converter starts operation,
LDO mode needs to be disabled. The following sequence is required to configure charger without BATFET.
1. Before adapter plugs in, put the charger into HIZ mode. (either pull pin 6 ILIM_HIZ to ground, or set
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