BQ25708 datasheet(61/94 Pages) TI2

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between the system and battery is the VDS of BATFET. System voltage is regulated 160 mV above battery

voltage when BATFET is off (no charging or no supplement current).

When BATFET is removed, the system node VSYS is shorted to SRP. Before the converter starts operation,

LDO mode needs to be disabled. The following sequence is required to configure charger without BATFET.

1. Before adapter plugs in, put the charger into HIZ mode. (either pull pin 6 ILIM_HIZ to ground, or set

REG0x35[7] to 1)

2. Set 0x00[2] to 0 to disable LDO mode.

3. Set 0x30[0] to 0 to disable auto-wakeup mode.

4. Check if battery voltage is properly programmed (REG0x05/04)

5. Set precharge/charge current (REG0x03/02)

6. Put the device out of HIZ mode. (Release ILIM_HIZ from ground and set REG0x35[7]=0).

In order to prevent any accidental SW mistakes, the host sets low input current limit (a few hundred milliamps)

when device is out of HIZ.

9.6.6 Input Current and Input Voltage Registers for Dynamic Power Management

The charger supports Dynamic Power Management (DPM). Normally, the input power source provides power for

the system load or to charge the battery. When the input current exceeds the input current setting, or the input

voltage falls below the input voltage setting, the charger decreases the charge current to provide priority to the

system load. As the system current rises, the available charge current drops accordingly towards zero. If the

system load keeps increasing after the charge current drops down to zero, the system voltage starts to drop. As

the system voltage drops below the battery voltage, the battery will discharge to supply the heavy system load.

9.6.6.1 Input Current Registers

To set the maximum input current limit, write a 16-bit IIN_HOST register command (REG0x0F/0E()) using the

data format listed in Table 9-29 and Table 9-30. When using a 10-mΩ sense resistor, the charger provides an

input-current limit range of 50 mA to 6400 mA, with 50-mA resolution. The default current limit is 3.25 A. Due

to the USB current setting requirement, the register setting specifies the maximum current instead of the typical

current. Upon adapter removal, the input current limit is reset to the default value of 3.25 A. With code 0, the

input current limit is 50 mA.

The ACP and ACN pins are used to sense RAC with the default value of 10 mΩ. For a 20-mΩ sense resistor, a

larger sense voltage is given and a higher regulation accuracy, but at the expense of higher conduction loss.

Instead of using the internal DPM loop, the user can build up an external input current regulation loop and have

the feedback signal on the ILIM_HIZ pin.

(

)

ILIM _ HIZ

ACP

ACN

DPM

1 40 I

= +

(2)

In order to disable ILIM_HIZ pin, the host can write to 0x32[7] to disable ILIM_HIZ pin, or pull ILIM_HIZ pin

above 4.0 V.

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BQ25713, BQ25713B

SLUSD83C – JUNE 2018 – REVISED MAY 2023

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