RT9481 datasheet(14/41 Pages) RICHTEK

14 / 41 page

RT9481

is a registered trademark of Richtek Technology Corporation.

www.richtek.com

DS9481-00 June 2015

Table 2. VPREC Register Setting Table

VPREC[2:0]

Pre-Charge Threshold

0000

2.3V

0001

2.4V

0010

2.5V

0011

2.6V

0100

2.7V

0101

2.8V

0110

2.9V

0111

3V (default)

1000

3.1V

1001

3.2V

1010

3.3V

1011

3.4V

1100

3.5V

1101

3.6V

1110

3.7V

1111

3.8V

Table 3. IPREC Register Setting Table

IPREC[1:0]

Pre-Charge Current

200mA

300mA (default)

400mA

500mA

Fast-Charge Mode and Settings

As the ISENSN pin rises above VPREC, the charger

enters fast-charge mode and starts switching. Notice

that the switching charger does not integrate input

power source (AC adapter or USB input) detection.

Thus, the switching charger does not set the charge

current automatically. Unlike the linear charger (LDO),

the switching charger (Buck converter) is a current

amplifier. The current drawn by the switching charger

is different from the current into the battery. The user

can set the Average Input Current Regulation (AICR)

and output charge current (ICHRG) respectively.

Cycle-by-Cycle Current Limit

The

charger

the

switching

charger

has

embedded cycle-by-cycle current limit for inductor.

Once the inductor current touches the threshold, the

charger stops charging immediately to prevent over

current from damaging the device. Notice that, the

mechanism cannot be disabled by any way.

Average Input Current Regulation (AICR)

The AICR levels are 100mA to 2A programmed by I2C

per 50mA.

Charge Current (ICHRG)

The charge current into the battery is determined by

the sense resistor (RSENSE) and ICC setting by I

2C.

The voltage between the ISENSP and ISENSN pins is

regulated to the voltage control by ICC setting.

As the RSENSE is 10m, the Fast-Charge currents are

700mA to 2.7A programmed by I2C per 250mA.

Table 4. ICHG Register Setting Table

ICHG[3:0]

VCC

ICHG RSENSE is 10m

0000

7mV

0.7A (default)

0001

9.5mV

0.95A

0010

12mV

1.2A

0011

14.5mV

1.45A

0100

17mV

1.7A

0101

1.95mV

1.95A

0110

2.2mV

2.2A

0111

2.45mV

2.45A

1000

2.7mV

2.7A

Constant Voltage Mode and Settings

The switching charger enters constant voltage mode

when the VBAT voltage is close to the output-charge

voltage (VBATREG). Once in this mode, the charge

current begins to decrease. For default settings

(charge current termination is disabled), the switching

charger does not turn off and always regulates the

battery voltage at VBATREG. However, once the charge

current termination is enabled, the charger terminates

if the charge current is below termination current (IEOC)

constant-voltage

mode.

The

charge

current

termination function is controlled by the I2C interface.

After termination, a new charge cycle restarts when

one of the following conditions is detected :



The ISENSN pin voltage falls below the VBATREG as

VREC threshold.



VBUS Power On Reset (POR).



Enable bit toggle or Charger reset (via I2C interface).

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