RT9458WSC datasheet(13/27 Pages) RICHTEK

13 / 27 page

DS9458-02

February 2017

www.richtek.com

RT9458

is a registered trademark of Richtek Technology Corporation.

Safety Timer in Charge Mode and in OTG Mode

To implement safety mechanism, the RT9458 has two

timer modes : T32min mode with a 32-minute timer for

charger mode and T32sec mode with a 32-second timer

for OTG mode.

In the charger mode, a the beginning of a charging

operation, the RT9458 enters T32min mode and starts a

32-minute timer that can be reset by any read or write

action performed by the host through the I2C interface. If

the 32-minute timer expires, the charging operation is

terminated and shows the fault bit CH32MI.

In the OTG mode, at the beginning of a OTG operation,

the RT9458 enters T32sec mode and starts a 32-second

timer that can be reset by any read or write action

performed by the host through the I

2C interface. If the 32-

second timer expires, the OTG operation will keep going

but shows the fault bit BST32SI.

Input Voltage Protection in Charge Mode

During charge mode, there are two protection mechanisms

against poor input power source.

Sleep Mode (VIN

−−−−− VBATS < VSLP)

The RT9458 enters sleep mode if the voltage drop between

the VIN and BATS pins falls below VSLP. In sleep mode,

the reverse blocking switch and PWM are all turned off.

This function prevents battery drain during poor or no input

power source.

Input Over-Voltage Protection

When VIN voltage rises above the input over-voltage

threshold (VINOVP), the RT9458 stops charging and then

sets fault status bits. The condition is released when VIN

falls below VINOVP

− VINOVP_Hys. The RT9458 then resumes

charging operation.

Boost Mode Operation (OTG)

IN_LIMIT

ICHRG

CHRG

SENSE

= MIN

















where D is the duty cycle and

η is the efficiency.

Constant Voltage Mode and Settings

The RT9458 enters constant voltage mode when the BATS

voltage is close to the output-charge voltage (VOREG). Once

in this mode, the charge current begins to decrease. For

default settings (charge current termination is disabled),

the RT9458 does not turn off and always regulates the

battery voltage at VOREG. However, once the charge current

termination is enabled, the charger terminates if the charge

current is below termination current (IEOC) in constant

voltage mode. The charge current termination function is

controlled by the I

2C interface in the

“TE” bit via the

After termination, a new charge cycle restarts when one

of the following conditions is detected :



The BATS pin voltage falls below the VOREG

− VRECH

threshold.



VIN Power On Reset (POR).



CHG_EN bit toggle or RST bit is set (via I

2C interface).

Output Charge Voltage (VOREG)

The output-charge voltage is set by the I2C interface in

the CV section (Bit2 to Bit7 bits) via the register of address

0x02. Its range is from 3.5V to 4.45V. The default is 4.2V

(100011).

Termination Current (IEOC)

If the end of charge detection and shutdown control for

EOC are both enable (TE bit =

“1”, TE_SHDN_EN bit =

“1”), the end-of-charge current is determined by both the

change current (ICHRG) and IEOC percentage. IEOC

percentage is set by the I2C interface in the IEOC section

via the register of address 0x05. Its range is from 50mA to

400mA with an step of 50mA.

When input current limit and charge current are both set,

the charge current in fast charge phase is calculated as

below :

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