BQ25703A Datasheet, PDF (22/81 Pages) Texas Instruments – I2C Multi-Chemistry Battery Buck-Boost Charge Controller With System Power Monitor and Processor Hot Monitor

bq25703A
SLUSCU1 – MAY 2017
www.ti.com
8.3 Feature Description
8.3.1 Power-Up from Battery Without DC Source
If only battery is present and the voltage is above V_{VBAT_UVLOZ}, the BATFET turns on and connects battery to
system. By default, the charger is in low power mode (REG0x01[7] = 1) with lowest quiescent current. The LDO
stays off. When device moves to performance mode (REG0x01[7] = 0), The host enables IBAT buffer through
I2C to monitor discharge current. For PSYS, PROCHOT or independent comparator, REGN LDO is enabled for
an accurate reference.
8.3.2 Power-Up From DC Source
When an input source plugs in, the charger checks the input source voltage to turn on LDO and all the bias
circuits. It sets the input current limit before the converter starts.
The power-up sequence from DC source is as follows:
1. 50 ms after VBUS above V_{VBUS_CONVEN}, enable 6 V LDO and CHRG_OK goes HIGH
2. Input voltage and current limit setup
3. Battery CELL configuration
4. 150 ms after VBUS above V_{VBUS_CONVEN}, converter powers up.
8.3.2.1 CHRG_OK Indicator
CHRG_OK is an active HIGH open drain indicator. It indicates the charger is in normal operation when the
following conditions are valid:
• VBUS is above V_{VBUS_CONVEN}
• VBUS is below V_ACOV
• No MOSFET/inductor fault
8.3.2.2 Input Voltage and Current Limit Setup
After CHRG_OK goes HIGH, the charger sets default input current limit in REG0x0F/0E() to 3.30 A. The actual
input current limit is the lower setting of REG0x0F/0E() and ILIM_HIZ pin.
Charger initiates a VBUS voltage measurement without load (VBUS at noLoad). The default VINDPM threshold
is VBUS at noLoad – 1.28 V.
After input current and voltage limits are set, the charger device is ready to power up. The host can always
update input current and voltage limit based on input source type.
8.3.2.3 Battery Cell Configuration
CELL_BATPRESZ pin is biased with resistors from REGN to CELL_BATPRESZ to GND. After VDDA LDO is
activated, the device detects the battery configuration through CELL_BATPRESZ pin bias voltage. Refer to
Electrical Characteristics for CELL setting thresholds.
CELL COUNT
4S
3S
2S
1S
Table 1. Battery Cell Configuration
PIN VOLTAGE w.r.t. VDDA
BATTERY VOLTAGE
(REG0x05/04)
75%
16.800V
55%
40%
25%
12.592V
8.400V
4.192V
SYSOVP
No SYSOVP
(Refer to System Overvoltage
Protection (SYSOVP) section)
18.5V
12V
5V
8.3.2.4 Device Hi-Z State
The charger enters Hi-Z mode when ILIM_HIZ pin voltage is below 0.4 V or REG0x35[7] is set to 1. During Hi-Z
mode, the input source is present, and the charger is in the low quiescent current mode with REGN LDO
enabled.
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