BQ25050 Datasheet, PDF (12/28 Pages) Texas Instruments – 1A, Single-Input, Single Cell Li-Ion Battery Charger with 50-mA LDO, External Power Path

bq25050
SLUSA33 – MARCH 2010
www.ti.com
TYPICAL CHARACTERISTICS (continued)
Using circuit in Figure 1, T_A = 25°C, unless otherwise specified
INPUT CURRENT LIMIT
vs
INPUT VOLTAGE
1000
900
4.00
VBAT = 3 V
3.90
OUTPUT VOLTAGE
vs
CHARGE CURRENT
800
Dropout Thermal Regulation
700
3.80
External Power Path Control Mode
VBAT = 3 V
3.70
600
3.60
500
3.50
400
3.40
300
3.30
200
3.20
100
3.10
0
4
5
6
7
8
9
10
11
V_IN - Input Voltage - V
Figure 19.
3.00
0.000
0.200
0.400
0.600
I_CHRG - Charge Current - mA
Figure 20.
0.800
1.000
DETAILED FUNCTIONAL DESCRIPTION
The bq25050 is a highly integrated Li-Ion linear battery charger targeted at space-limited portable applications. It
operates from either a USB port or AC Adapter and charges a single-cell Li-Ion battery with up to 1A of charge
current. The 30V input voltage range with input over-voltage protections supports low-cost unregulated adapters.
The bq25050 has a single power output that charges the battery. The system load is connected to OUT. The
low-battery system startup circuitry maintains OUT pin voltage at V_OUT(REG) whenever an input source is
connected. This allows the system to start-up and run whenever an input source is connected regardless of the
battery voltage. The charge current is programmable up to 1A using the CTRL input. Additionally, a 4.9V 50mA
LDO is integrated into the IC for supplying low power external circuitry.
External FET Controller (BGATE)
The External Power Path Control feature is implemented using the BGATE output. BGATE is also used to
enable/ disable the External Power Path Control feature. When power is first applied to either V_BAT or V_IN on the
bq25050, the BGATE output is tested. If the BGATE pin is connected to VSS, the External Power Path Control
feature is disabled. In order to enable the External Power Path Control feature after it has been disabled, the
battery and the input source must be removed and reconnected and BGATE must NOT be connected to VSS.
With External Power Path Control enabled, BGATE is used to drive an external P-channel MOSFET that
connects the battery to the system output. This state of this MOSFET is dependant on the battery voltage and
the IC status. In discharge mode, BGATE is pulled to GND to turn the MOSFET on fully. During discharge mode,
the output is connected directly to the battery. Discharge mode is entered under the following conditions:
1. IC disabled or no input power
2. Supplement mode
3. "Force On" – enabled through CTRL
When not in one of these conditions, the BGATE output is controlled by the bq25050 and changes depending on
which mode is required. See the Charging Operation section for more details.
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