BQ25606 Datasheet, PDF (21/43 Pages) Texas Instruments – Standalone 3.0-A, Single Cell Battery Charger With 40V Over Voltage Protection Controller

bq25606
www.ti.com
SLUSCK6 – MAY 2017
8.3.6.6 Charging Safety Timer
The device has built-in safety timer to prevent extended charging cycle due to abnormal battery conditions. The
safety timer is 2 hours when the battery is below V_BATLOWV threshold and 10 hours when the battery is higher
than V_BATLOWV threshold.
During input voltage, current, JEITA cool or thermal regulation, the safety timer counts at half clock rate as the
actual charge current is likely to be below the register setting. For example, if the charger is in input current
regulation throughout the whole charging cycle, the safety timer will expire in 20 hours.
During the fault, timer is suspended. Once the fault goes away, fault resumes. If user stops the current charging
cycle, and start again, timer gets reset.
8.3.6.7 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.
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..
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
8.3.6.8 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.
Figure 16 shows the DPM response with 9-V/1.2-A adapter, 3.2-V battery, 2.8-A charge current and 3.5-V
minimum system voltage setting.
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