BQ25708 datasheet(25/94 Pages) TI2

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9.3.3.2 Input Voltage and Current Limit Setup

After CHRG_OK goes HIGH, the charger sets default input current limit in REG0x0F/0E() to 3.25 A. The actual

input current limit being adopted by the device is the lower setting of REG0x0F/0E() and ILIM_HIZ pin.

Charger initiates a VBUS voltage measurement without any load (VBUS at no load) right before the converter is

enabled. The default VINDPM threshold is VBUS at no load – 1.28 V.

After input current and voltage limits are set, the charger device is ready to power up. The host can always

program the input current and voltage limit after the charger being powered up, based on the input source type.

9.3.3.3 Battery Cell Configuration

CELL_BATPRESZ pin is biased with a resistor divider 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 Table 9-1 for cell setting thresholds.

Table 9-1. Battery Cell Configuration

CELL COUNT

PIN VOLTAGE w.r.t. VDDA

BATTERY VOLTAGE

(REG0x05/04)

SYSOVP

75%

16.800 V

19.5 V

55%

12.592 V

19.5 V

40%

8.400 V

12 V

25%

4.192 V

5 V

9.3.3.4 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.

9.3.4 USB On-The-Go (OTG)

The device supports USB OTG operation to deliver power from the battery to other portable devices through

USB port. The OTG mode output voltage is set in REG0x07/06(). The OTG mode output current is set in

REG0x09/08(). The OTG operation can be enabled if the conditions are valid:

• Valid battery voltage is set REG0x05/04(), the battery voltage should not trip the BATOVP threshold,

otherwise, the converter will stop switching.

• OTG output voltage is set in REG0x07/06() and REG0x34[2], if REG0x34[2] = 0, the VOTG digital DAC is

offset by 1.28V to achieve higher range from 4.28V~20.8V, if REG0x34[2] = 1, the VOTG digital DAC is from

3V to 19.52V.

• OTG output current is set in REG0x09/08().

• EN_OTG pin is HIGH, REG0x35[4] = 1 and REG0x34[5] = 1.

• VBUS is below VVBUS_CONVENZ.

• 10 ms after the above conditions are valid, converter starts and VBUS ramps up to target voltage. CHRG_OK

pin goes HIGH if REG0x01[3] = 1.

9.3.5 Converter Operation

The charger employs a synchronous buck-boost converter that allows charging from a standard 5-V or a

high-voltage power source. The charger operates in buck, buck-boost and boost mode. The buck-boost can

operate uninterruptedly and continuously across the three operation modes.

Table 9-2. MOSFET Operation

MODE

BUCK

BUCK-BOOST

BOOST

Switching

OFF

Switching

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BQ25713, BQ25713B

SLUSD83C – JUNE 2018 – REVISED MAY 2023

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