BQ24296_15 Datasheet, PDF (21/55 Pages) Texas Instruments – bq2429x I2C Controlled 3-A Single Cell USB Charger With Narrow VDC Power Path Management and Adjustable Voltage USB OTG

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bq24296, bq24297
SLUSBP6B – SEPTEMBER 2013 – REVISED NOVEMBER 2014
4.5
4.3
4.1
SYS
(V)
3.9
3.7
Charge Enabled
Charge Disabled
3.5
Minimum System Voltage
3.3
3.1
2.7 2.9 3.1 3.3 3.5 3.7 3.9 4.1 4.3
BAT (V)
Figure 13. V(SYS) vs V(BAT)
9.3.2.2 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 (REG00[2:0]) or the voltage
falls below the input voltage limit (REG00[6:3]). 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 (either VINDPM or IINDPM), the status register REG08[3] will go high.
Figure 14 shows the DPM response with 5-V/1.2-A adapter, 3.2-V battery, 2.0-A charge current and 3.4-V
minimum system voltage setting.
Voltage
5V
VBUS
3.6V
3.4V
3.2V
3.18V
SYS
BAT
Current
3A
2.3A
2.0A
ISYS
ICHG
1.5A
1.0A
IIN
0.5A
-0.7A
DPM
DPM
Supplement
Figure 14. DPM Response
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