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RT9719 Datasheet(PDF) 7 Page - Richtek Technology Corporation

Part No. RT9719
Description  Charging System Safety Device
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Maker  RICHTEK [Richtek Technology Corporation]
Homepage  http://www.richtek.com
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RT9719 Datasheet(HTML) 7 Page - Richtek Technology Corporation

 
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RT9719
7
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
Y
YY
N
N
N
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
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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