Document
RT9709
Integrated Over Voltage Protection Circuit
General Description
The RT9709 is an integrated circuit (IC) optimized to protect low voltage system from abnormal high voltage input up to 28V. The IC monitors the input voltage, battery voltage and the charging current to make sure all three parameters are operated in normal range. It also monitors its own temperature and turns the MOSFET off when the chip temperature exceeds 140°C.
The RT9709 can supportAC charger or USB charger. When the input voltage exceeds the OVP threshold, the IC turns off the MOSFET within 1us to remove the power before any damage occurs.
The current in the MOSFET is also limited to prevent charging the battery with an excessive current. The current limit can be programmed by an external resistor between ILIM and GND. The OCP function has a 4-bit binary counter that accumulates during an OCP event. When the total count reaches 16 times, the MOSFET will be turned off permanently unless the input power is recycled.
The IC also monitors the battery voltage VB. When the battery voltage exceeds 4.4V and last for more than 180us the RT9709 will turn off the MOSFET. The internal logic control will turn off and latch the MOSFET when the battery over-voltage event reaches 16 times.
Pin Configurations
(TOP VIEW)
VIN 1 VIN 2 GND 3
WRN 4 NC 5 NC 6
GND 13
12 NC 11 VOUT 10 VOUT 9 ILIM 8 VB 7 EN
WDFN-12L 4x3
VIN 1
VIN 2 GND 3 WRN 4
NC 5
GND 11
9
10 VOUT 9 VOUT 8 ILIM 7 VB
EN
WDFN-10L 3x3
Features
z Fully Integrated Protection Circuit for Three Protection Variables ` User Programmable OCP Threshold ` Input OVP Less than 1us ` Battery OVP
z Up to 30V Over Voltage Protection z High Accuracy Protection Threshold z High Immunity of False Triggering Under Transients z Warning Indication Output z Enable Input z Thermally Enhanced WDFN Package z RoHS Compliant and Halogen Free
Applications
z Cellular Phones z Digital Cameras z PDAs and Smart Phones z Portable Instruments
Ordering Information
RT9709
Note :
Package Type QW : WDFN-12L 4x3 (W-Type) QWB : WDFN-10L 3x3 (W-Type)
Lead Plating System G : Green (Halogen Free and Pb Free) OVP Default : 6.8V A : 5.85V B : 6.25V
Richtek products are :
` RoHS compliant and compatible with the current requirements of IPC/JEDEC J-STD-020.
` Suitable for use in SnPb or Pb-free soldering processes.
Marking Information
For marking information, contact our sales representative directly or through a Richtek distributor located in your area.
DS9709-02 April 2011
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RT9709
Typical Application Circuit
VIN CIN
WRN
RT9709/A/B VIN VOUT
VIN VOUT
GND
VB
WRN NC
ILIM EN
Charger
RVB
+ Battery EN RILIMIT
Functional Pin Description
Pin No. WDFN-12L 4x3 WDFN-10L 3x3
1, 2 1, 2
Pin Name VIN
Pin Function Input Power Source Pin.
3 4 5, 6, 12
3
GND
Ground Pin.
This is an open-drain logic output that turns LOW when any 4 WRN
protection event occurs.
5 NC No Internal Connection.
7 6 EN Enable Input Pin. Pull this pin to low or leave it floating to enable the IC. Force this pin to high to disable the IC.
Battery Voltage Monitoring Input Pin. This pin is connected to 8 7 VB
the battery pack positive terminal via resistor.
9 10, 11
8 9, 10
ILIM VOUT
Over-Current Protection Threshold Setting Pin. Connect a resistor between this pin and GND to set the OCP threshold. Output Voltage Pin. Output through the MOSFET.
13 (Expose Pad) 11 (Exposed Pad) GND
The exposed pad must be soldered to a large PCB and connected to GND for maximum thermal dissipation.
Function Block Diagram
VIN VOUT
VREF Ibias VDD
BASE Driver
OCP
OCP Seting
ILIM
INOVP UVLO
Control Logic
BATOVP
Buffer
VB
EN EN Logic
OTP
WRN GND
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DS9709-02 April 2011
RT9709
Absolute Maximum Ratings (Note 1)
z Supply Input Voltage, VIN -------------------------------------------------------------------------------------------- −0.3V to 30V z VOUT, VB --------------------------------------------------------------------------------------------------------------- −0.3V to 7V z Other Pins --------------------------------------------------------------------------------------------------------------- −0.3V to 5.5V z Power Dissipation, PD @ TA = 25°C
WDFN-10L 3x3 --------------------------------------------------------------------------------------------------------- 1.429W WDFN-12L 4x3 --------------------------------------------------------------------------------------------------------- 1.667W z Package Thermal Resistance (Note 2) WDFN-10L 3x3, θJA --------------------------------------------------------------------------------------------------- 70°C/W WDFN-10L 3x3, θJC --------------------------------------------------------------------------------------------------- 7°C/W WDFN-12L 4x3, θJA --------------------------------------------------------------------------------------------------- 60°C/W WDFN-12L 4x3, θJC --------------------------------------------------------------------------------------------------.