BQ25601 Datasheet, PDF (24/60 Pages) Texas Instruments – I2C Controlled 3-A, Single-Cell Battery Charger for High Input Voltage and Narrow Voltage DC (NVDC) Power Path Management

bq25601
SLUSCK5 – MARCH 2017
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8.4.7.8 Narrow VDC Architecture
The device deploys Narrow VDC architecture (NVDC) with BATFET separating system from battery. The
minimum system voltage is set by SYS_Min bits. Even with a fully depleted battery, the system is regulated
above the minimum system voltage (default 3.5 V).
When the battery is below minimum system voltage setting, the BATFET operates in linear mode (LDO mode),
and the system is typically 180 mV above the minimum system voltage setting. As the battery voltage rises
above the minimum system voltage, BATFET is fully on and the voltage difference between the system and
battery is the VDS of BATFET.
When the battery charging is disabled and above minimum system voltage setting or charging is terminated, the
system is always regulated at typically 50mV above battery voltage. The status register VSYS_STAT bit goes
high when the system is in minimum system voltage regulation.
4.5
Charge Disabled
4.3
Charge Enabled
Minimum System Voltage
4.1
3.9
3.7
3.5
3.3
3.1
2.7 2.9 3.1 3.3 3.5 3.7 3.9 4.1 4.3
BAT (V)
D002
Plot1
Figure 15. System Voltage vs Battery Voltage
8.4.7.9 Dynamic Power management
To meet maximum current limit in USB spec and avoid over loading the adapter, the device features Dynamic
Power management (DPM), which continuously monitors the input current and input voltage. When input source
is over-loaded, either the current exceeds the input current limit (IIDPM) or the voltage falls below the input
voltage limit (VINDPM). The device then reduces the charge current until the input current falls below the input
current limit and the input voltage rises above the input voltage limit.
When the charge current is reduced to zero, but the input source is still overloaded, the system voltage starts to
drop. Once the system voltage falls below the battery voltage, the device automatically enters the supplement
mode where the BATFET turns on and battery starts discharging so that the system is supported from both the
input source and battery.
During DPM mode, the status register bits VDPM_STAT (VINDPM) or IDPM_STAT (IINDPM) goes high.
Figure 16 shows the DPM response with 9-V/1.2-A adapter, 3.2-V battery, 2.8-A charge current and 3.4-V
minimum system voltage setting.
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