RT9451 datasheet(30/37 Pages) RICHTEK

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RT9451

DS9451-00

September 2013

www.richtek.com

is a registered trademark of Richtek Technology Corporation.

Recharge Behavior

There are two recharge behavior depending on

CH_EN [1:0] setting. If CH_EN [1:0] =

“11”, the RT9451

will recharge automatically once BATS falls below VOREG

−

VRECH threshold. If CH_EN [1:0] = “10”, the RT9451 will

not recharge automatically but set CHRECH flag and pull

low INT pin to notify the host the battery need to be

recharged.

Safety Timer in Charge Mode

To implement safety mechanism in charge mode, the

RT9451 has a 32-minute timer. At the beginning of a

charging operation, the RT9451 starts 32-minute timer

that can be reset by any write or read action performed by

the host through the I2C interface. Once 32-minute timer

is expired, the RT9451 enters to high impedance mode.

The I2C registers are all reset to default value and CH32M

bit is set to

“1” to prevent the charger against uncontrolled

charging when the dead lock of the host occurs.

During normal charging process, the host needs to reset

32-minute timer periodically.

Input Voltage Protection in Charge Mode

During charge mode, there are three protection

mechanisms against poor input power source and over-

voltage condition : bad adapter detection, sleep mode and

input over-voltage protection.

Bad Adapter Detection (CHBADI)

A mechanism is used to justify the power source capability

when power on at the VIN pin. When VIN rises above

VIN(MIN), a sink current of 30mA (typ.) is connected to VIN

pin to detection adaptor status. After the detection period

(30ms typ.), the sink current is removed. At the same

time, if VIN is still above VIN(MIN), the detection passes

and enters charge mode. If VIN is below VIN(MIN), the bad

adapter condition occurs. The RT9451 stops working, sets

CHBADI and repeats detection flow every 2 second (typ.).

Sleep Mode (VIN - VBATS < VSLP, CHRVPI)

The RT9451 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 (VINOVPI)

When VIN voltage raises above the input over-voltage

threshold (VOVP_IN), the RT9450 stops charging and then

sets fault status bits and sends out fault pulse via the

STAT pin. The condition is released when VIN falls below

VOVP_IN VOVP_IN. The RT9450 then resumes charging

operation.

Boost Mode Operation (OTG)

Trigger and Operation

The RT9451 features USB OTG support. There are two

trigger method : One is to set CH_EN [1:0] =

“01” (for

I2C control), the other is to set OTG_EN, OTG_PL and

OTG pin (for GPIO control). Notice that when using OTG

pin to trigger boost mode, it needs an edge trigger and

then keep it to the level defined by OTG_PL. When OTG

function is enabled, the synchronous Boost control loop

takes over the power MOSFETs and reverses the power

flow from the battery to the VIN pin. In normal boost mode,

the MID pin is regulated to the voltage level determined

by VOREG [5:0] whose range is from 4.75 and provides

up to 1.6A current to support other USB OTG devices

connected to the USB connector.

Safety Timer in Boost Mode (BST32SI)

Initially, the RT9451 starts a 32-second timer that can be

reset by any write or read action performed by the host

through the I2C interface. Once 32-second timer is expired,

the RT9451 enters to high impedance mode, the I2C

registers are all reset to default value and BST32S bit is

set to

“1” to prevent the charger against uncontrolled

discharging when the dead lock of the host occurs.

During normal discharging process, the host needs to

reset 32-second timer periodically.

Output Over-Voltage Protection (VIN pin,

BSTVINOVI)

In boost mode, the output over-voltage protection is

triggered when the VIN voltage is above the output OVP

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