Richtek RT8452GQW, RT8452GS Schematic [ru]
Conceptual |
RT8452 |
High Voltage High Current LED Driver |
Controller for Boost |
or Buck-Boost Topology |
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General Description
The RT8452 is a current mode PWM controller designed to drive an external MOSFET for high current LED applications. With a current sense amplifier threshold of 180mV, the LED current is programmable with one external current sense resistor and the power loss is minimized. With the maximum operating input voltage of 40V and output voltage up to 60V, the RT8452 is ideal for boost or buck-boost operation. (See RT8450 and RT8451 for buck mode LED driver application.)
With 1MHz operating frequency, the external inductor and capacitors can be small while mainteining high efficiency.
Dimming can be either analog or PWM digital. The unique built-in clampping comparator and filter allow easy low noise analog dimming conversion from PWM signal with only one external capacitor. PWM dimming control is made easy with a build in FET driver dedicated for the extermal dimming MOSFET.
The RT8452 is available in WQFN-16L 3x3 and SOP-16 packages.
Features
•High Voltage Capability : VIN Up to 40V, VOUT Up to 60V
•Boost or Buck-Boost Operation
•Current Mode PWM with 1MHz Switching Frenquency
•Easy Dimming : Analog, PWM Digital or PWM Converting to Analog with One External Capacitor
•Programmable Soft Start to Avoid Inrush Current
•Programmable Over Voltage Protection to Limit Output Voltage
•VIN Undervoltage Lockout and Thermal Shutdown
•16-Lead WDFN and SOP Packages.
•RoHS Compliant and 100% Lead (Pb)-Free
Applications
•General Industrial High Power LED Lighting
•Desk Lights and Room Lighting
•Building and Street Lighting
•Industrial Display Backlight
Ordering Information
RT8452 
Package Type
S : SOP-16
QW : WDFN-16L 3x3 (W-Type)
Operating Temperature Range
G : Green (Halogen Free with Commercial Standard)
Note :
Richtek Green 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. }100% matte tin (Sn) plating.
Marking Information
For marking information, contact our sales representative directly or through a Richtek distributor located in your area, otherwise visit our website for detail.
Pin Configurations
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GND |
VCC |
OVP |
EN |
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16 |
15 |
14 |
13 |
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GBIAS |
1 |
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12 |
NC |
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GATE |
2 |
GND |
11 |
SS |
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PWMOUT |
3 |
10 |
DCTL |
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ISW |
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17 |
ACTL |
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4 |
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9 |
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5 |
6 |
7 |
8 |
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PWMDIM |
ISP |
ISN |
VC |
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WQFN-16L 3x3 |
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GBIAS |
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GND |
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16 |
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GATE |
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2 |
15 |
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VCC |
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PWMOUT |
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3 |
14 |
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OVP |
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ISW |
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4 |
13 |
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EN |
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PWMDIM |
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5 |
12 |
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NC |
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ISP |
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6 |
11 |
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SS |
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ISN |
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7 |
10 |
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DCTL |
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VC |
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8 |
9 |
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ACTL |
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SOP-16
DS8452-02C March 2008 |
www.richtek.com |
1
RT8452 |
Conceptual |
Typical Application Circuit
VOUT
60V MAX
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L |
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R2 |
VIN |
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10uH |
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180mV |
4.5V to 40V |
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C1 |
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C5 |
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RT8452 |
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1uF |
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15 |
VCC |
GATE 2 |
R3 |
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5V |
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13 |
EN |
ISW 4 |
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Analog |
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9 |
ACTL |
ISP 6 |
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Dimming |
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10 |
DCTL |
ISN |
7 |
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R4 |
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8 |
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OVP 14 |
VOUT |
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VC |
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R1 |
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PWMOUT |
3 |
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11 |
SS |
R5 |
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10k |
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PWMDIM 5 |
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C3 |
1 |
GBIAS |
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C2 |
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GND |
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10nF |
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3nF |
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C4 |
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16, Exposed Pad (17) |
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Figure 1. Analog Dimming in Boost Configuration
VOUT
60V MAX
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L |
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R2 |
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VIN |
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10uH |
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180mV |
4.5V to 40V |
C1 |
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C6 |
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RT8452 |
1uF |
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15 |
VCC |
GATE 2 |
R3 |
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5V |
13 |
EN |
ISW 4 |
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PWM |
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10 |
DCTL |
ISP 6 |
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Dimming control |
8 |
VC |
ISN 7 |
R4 |
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R1 |
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11 |
SS |
OVP 14 |
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VOUT |
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PWMOUT 3 |
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10k |
C3 |
1 |
GBIAS |
R5 |
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C2 |
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PWMDIM 5 |
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10nF |
9 ACTL |
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3nF |
C4 |
GND |
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C5 |
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16, Exposed Pad (17) |
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0.5uF |
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Figure 2. PWM to Analog Dimming in Boost Configuration
VOUT
60V MAX
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L |
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R2 |
VIN |
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10uH |
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180mV |
4.5V to 40V |
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C1 |
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C5 |
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RT8452 |
1uF |
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15 |
VCC |
GATE 2 |
R3 |
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5V |
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13 |
EN |
ISW 4 |
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9 |
ACTL |
ISP 6 |
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10 |
DCTL |
ISN 7 |
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8 |
VC |
PWMOUT 3 |
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R1 |
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11 |
SS |
PWMDIM 5 |
R4 |
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OVP 14 |
VOUT |
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10k |
C3 |
1 |
GBIAS |
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C2 |
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GND |
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10nF |
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R5 |
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3nF |
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C4 |
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16, Exposed Pad (17) |
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Figure 3. True PWM Dimming in Boost Configuration
www.richtek.com |
DS8452-02C March 2008 |
2
Conceptual |
RT8452 |
VOUT
60V MAX
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L |
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VIN |
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10uH |
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4.5V to 40V |
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C1 |
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RT8452 |
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C5 |
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15 |
VCC |
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GATE |
2 |
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1uF |
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R3 |
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5V |
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13 |
EN |
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ISW |
4 |
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R2 |
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Analog |
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9 |
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ACTL |
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ISN |
7 |
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180mV |
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Dimming |
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10 |
DCTL |
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6 |
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ISP |
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8 |
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3 |
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VC |
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PWMOUT |
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R1 |
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11 |
SS |
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PWMDIM |
5 |
R4 |
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10k |
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1 |
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14 |
VOUT |
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C3 |
GBIAS |
OVP |
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C2 |
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GND |
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10nF |
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R5 |
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3nF |
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C4 |
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16, Exposed Pad (17) |
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Figure 4. Analog Dimming in Buck-Boost Configuration
Functional Pin Description
SOP-16 |
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QFN3X3-16 |
Pin Name |
Pin Function |
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1 |
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1 |
GBIAS |
The Internal Gate Driver Bias Pin.A good bypass capacitor is required. |
2 |
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2 |
GATE |
The External MOSFET Switch Gate Driver Output Pin. |
3 |
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3 |
PWMOUT |
The Output Pin for the PWM Dimming FET Driver. |
4 |
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4 |
ISW |
The External MOSFET Switch Current Sense Pin. Connect the current |
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sense resistor between external N-MOSFET switch and the ground. |
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5 |
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5 |
PWMDIM |
The Control Input Pin for the PWM Dimming FET Driver. |
6 |
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6 |
ISP |
The LED Current Sense Amplifier Positive Input. |
7 |
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7 |
ISN |
The LED Current Sense Amplifier Negative Input. Voltage |
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threshold between ISP and ISN is 180mV. |
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8 |
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8 |
VC |
The PWM Control Loop Compensation Pin. |
9 |
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9 |
ACTL |
The Analog Dimming Control Pin. The effective programming |
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voltage range of the pin is between 0.3V and 1.2V. |
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By adding a 0.1uF filtering capacitor on ACTL pin, the PWM dimming |
10 |
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10 |
DCTL |
signal on DCTL pin can be averaged and converted into analog |
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dimming signal on the ACTL pin following the formula below. |
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VACTL = 1.2V x PWM Dimming Duty Cycle. |
11 |
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11 |
SS |
The Soft-Start Pin. A capacitor of at least 10nF is required for proper |
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soft start. |
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12 |
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12 |
NC |
No Internal Connection. |
13 |
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13 |
EN |
The Chip Enable (Active High) Pin. When this pin voltage is low, the |
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chip is in shutdown mode. |
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14 |
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14 |
OVP |
The Over Voltage Protection Pin. The PWM converter turns off when |
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The voltage of the pin goes higher than 1.2V. |
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15 |
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15 |
VCC |
The Power Supply Pin of the Chip. For good bypass, a low ESR |
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Capacitor is required. |
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16 |
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16 |
GND |
The Ground Pin. The exposed pad must be soldered to a large PCB |
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Exposed Pad (17) |
And connected to GND for maximum power dissipation. |
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DS8452-02C |
March 2008 |
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www.richtek.com |
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