RT9719 datasheet(7/10 Pages) RICHTEK

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RT9719

DS9719-01 April 2011

www.richtek.com

Application information

Operation State

The operation state can be shown as following Figure 1.

At power-off state, the RT9719 will check whether VIN is

> UVLO threshold. If the VIN is higher than the UVLO

threshold, the RT9719 will check whether the Junction

temperature is over the OTP threshold. If the Junction

temperature is higher than the OTP threshold, the internal

P-MOSFET will be turned off. If the Junction temperature

is lower than the OTP threshold, the RT9719 will check

whether VIN is higher than the OVP threshold or not, if the

VIN is higher than the OVP threshold, the RT9719 will

turn off the internal P-MOSFET immediately within 1us.

And, if all of the checks including VIN > UVLO, TJ < OTP

and VIN < OVP are ok, the IC will operate normally.

Start

VIN > UVLO

TJ > OTP

VIN > OVP

Power-Off

Status

OTP Status

PFET=OFF

OVP Status

P-MOSFET = Off(Fast)

Normal Status

P-MOSFET = ON

and Control by

GATEDRV

Figure 1. Operation State Diagram for OVP Function

Input Over Voltage Protection (OVP)

The RT9719 monitors input voltage to prevent the input

voltage lead to output system failures. When the input

voltage exceeds the threshold, the RT9719 will turn off

the power MOSFET within 1us to prevent the high input

voltage from damaging the electronics in the handheld

system. The hysteresis for the input OVP threshold is

100mV. When the input voltage returns to normal

operation voltage range, the RT9719 re-enables the

MOSFET. The RT9719 allows the input voltage to rise up

to 30V without damaging the IC.

Battery Voltage Monitor

The RT9719 monitors the battery voltage by the ISENSE

pin. When the battery voltage exceeds the voltage level

of (VACIN

− 0.2V), the RT9719 will turn off the MOSFET

and the battery will not be charged. The RT9719 will

recharge the battery when the battery voltage is lower

than the voltage of (VACIN

− 0.2V).

Internal Over Temperature Protection

The RT9719 monitors its own internal temperature to

prevent thermal failures. When the internal temperature

reaches 140

°C with a built-in hysteresis of 20°C, the IC

turns off the power MOSFET. The IC does not resume

operation until the internal temperature drops below 120

°C.

Input Under Voltage Protection (UVLO)

The RT9719 monitors input voltage to prevent the input

voltage lead to output system failures. The RT9719 input

under voltage protection threshold is set to 2.7V. When

the input voltage is under the threshold, the RT9719 will

turn off the power MOSFET within 1us. When the input

voltage returns to normal operation voltage range, the

RT9719 re-enables the MOSFET.

RT9719

ACIN

GND

CHRIN

ISENSE

GATEDRV

VACIN

CIN

COUT

1µF

0.2

SOC

CHRIN

GATEDRV

ISENSE

VBAT

1µF

Battery

Figure 2. Application Diagram of RT9719 with SOC

Figure 2 shows the connection of RT9719 in a system

diagram. The ISENSE pin of the SOC will sense the voltage

of the 0.2

Ω sense resistor and the voltage of the VBAT

pin. The GATEDRV pin of the SOC can control the

MOSFET of the RT9719 to determine the level of the charge

current. The power of the SOC is provided by the CHRIN

pin of the RT9719. The RT9719 provides OVP function,

once the input voltage at the ACIN pin is higher than the

OVP level, the RT9719 will be shutdown to prevent the

SOC from damaging. If the voltage of the battery connected

to the VBAT pin is full, the RT9719 stops charging by

turning off the ISENSE pin. Input and output capacitors of

1uF are recommended to place as close to IC as possible.

Thermal Considerations

The maximum power dissipation depends on the thermal

resistance of IC package, PCB layout, the rate of

surroundings airflow and temperature difference between

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