BQ25708 datasheet(46/77 Pages) TI2

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bq25708

SLUSCU2 – NOVEMBER 2017

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8.6.3 ChargeCurrent Register (SMBus address = 14h) [reset = 0h]

To set the charge current, write a 16-bit ChargeCurrent() command (REG0x14()) using the data format listed in

Figure 22

With 10-mΩ sense resistor, the charger provides charge current range of 64 mA to 8.128 A, with a 64-mA step

resolution. Upon POR, ChargeCurrent() is 0 A when auto wakeup is not active. Any conditions for CHRG_OK low

except ACOV will reset ChargeCurrent() to zero. CELL_BATPRESZ going LOW (battery removal) will reset the

ChargeCurrent() register to 0 A.

Charge current is not reset in ACOC, TSHUT, power path latch off (REG0x30[1]), and SYSOVP.

A 0.1-µF capacitor between SRP and SRN for differential mode filtering is recommended; an optional 0.1-µF

capacitor between SRN and ground, and an optional 0.1-µF capacitor between SRP and ground for common

mode filtering. Meanwhile, the capacitance on SRP should not be higher than 0.1 µF in order to properly sense

the voltage across SRP and SRN for cycle-by-cycle current detection.

The SRP and SRN pins are used to sense voltage drop across RSR with default value of 10 mΩ. However,

resistors of other values can also be used. For a larger sense resistor, a larger sense voltage is given, and a

higher regulation accuracy; but, at the expense of higher conduction loss. A current sensing resistor value no

more than 20 mΩ is suggested.

Figure 22. ChargeCurrent Register With 10-mΩ Sense Resistor (SMBus address = 14h) [reset = 0h]

Reserved

Charge

Current, bit 6

Charge

Current, bit 5

Charge

Current, bit 4

Charge

Current, bit 3

Charge

Current, bit 2

R/W

Charge

Current, bit 1

Charge

Current, bit 0

Reserved

R/W

LEGEND: R/W = Read/Write; R = Read only; -n = value after reset

Table 25. Charge Current Register (14h) With 10-mΩ Sense Resistor (SMBus address = 14h) Field

Descriptions

SMBus

BIT

FIELD

TYPE

RESET

DESCRIPTION

15-13

Reserved

R/W

000b

Not used. 1 = invalid write.

Charge Current, bit 6

R/W