BQ25606 Datasheet, PDF (16/43 Pages) Texas Instruments – Standalone 3.0-A, Single Cell Battery Charger With 40V Over Voltage Protection Controller

bq25606
SLUSCK6 – MAY 2017
8.3 Feature Description
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8.3.1 Device Power Up from Battery without Input Source
If only battery is present and the voltage is above depletion threshold (V_{BAT_DPL_RISE)}, the BATFET turns on and
connects battery to system. The REGN stays off to minimize the quiescent current. The low RDSON of BATFET
and the low quiescent current on BAT minimize the conduction loss and maximize the battery run time.
The device always monitors the discharge current through BATFET (Supplement Mode). When the system is
overloaded or shorted (I_BAT > I_{BATFET_OCP}), the device turns off BATFET immediately until the input source plugs
in again.
8.3.2 Power Up from Input Source
When an input source is plugged in, the device checks the input source voltage to turn on REGN LDO and all the
bias circuits. It detects and sets the input current limit before the buck converter is started. The power up
sequence from input source is as listed:
1. Power Up OVPFET
2. Power Up REGN LDO
3. Poor Source Qualification
4. IInput Source Type Detection is based on D+/D– to set input current limit (IINDPM) .
5. Input Voltage Limit Threshold Setting (VINDPM threshold)
6. Converter Power-up
8.3.2.1 Power Up OVPFET
The external OVPFET provides an additional layer of voltage protection for the device. The external OVPFET is
enabled when all the below conditions are valid.
• VAC above V_{VAC_PRESENT}
• VAC below V_BAT + V_SLEEP in boost mode
• VAC below V_{VAC_OV}
• After t_DEB (15ms nom.) delay is completed
If one of the above conditions is not valid, the device is in high impedance state (HIZ) with REGN LDO off. The
device draws less current (I_{VBUS_HIZ}) from VBUS during a HIZ state. The battery powers the system when the
device is in a HIZ state.
As shown in Figure 11, V_{VAC_PRESENT(rising)} < V_VAC < V_{VAC_OV(rising)} must be valid before ACDRV goes high.
VAC
t_DEB
V_{VAC_OV (rising)}
V_{VAC_PRESENT (rising)}
t_{ON_VBUS}
90%
ACDRV
10%
VBUS
90%
10%
Time
Figure 11. OVPFET Startup Control
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