RT8562
High Voltage 8 Channel LED Driver
Features
z High Voltage : VIN up to 24V, VOUT up to 40V, Driving up to 80 x 3.6V LEDs (10 each channel)
z Channel Current Programmabe 10mA to 30mA and
Matched to 1.5%
z Current Mode PWM 1MHz Boost Converter z Easy Analog and Digital Dimming Control z Programmable Soft Start
z Automatic Detecting Unconnected and/or Broken
Channel
z Programmable Over Voltage Protection z Disconnects LED in Shutdown
z Providing High Accuracy Digital Dimming by PWM
Signal
z VIN Under Voltage Lockout
z Over Temperature Protection
z Current Limiting Protection
z Small 24-Lead WQFN Package
z RoHS Compliant and Halogen Free
Applications
z UMPC and Notebook Computer Backlight
z GPS, Portable DVD Backlight
z Desk Lights and Room Lighting
Pin Configurations
(TOP VIEW)
Ordering Information |
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VDC |
VIN |
COMP |
NC |
LX2 |
LX1 |
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RT8562 |
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Package Type |
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24 |
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22 |
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20 |
19 |
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QW : WQFN-24L 4x4 (W-Type) |
EN |
1 |
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18 |
PGND2 |
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Lead Plating System |
NC |
2 |
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17 |
PGND1 |
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SS |
3 |
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16 |
OVP |
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G : Green (Halogen Free and Pb Free) |
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GND |
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Note : |
NC |
4 |
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15 |
CH1 |
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Richtek products are : |
GND |
5 |
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14 |
CH2 |
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25 |
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` RoHS compliant and compatible with the current require- |
PWM |
6 |
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13 |
CH3 |
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7 |
8 |
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11 |
12 |
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ments of IPC/JEDEC J-STD-020. |
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CH8 |
CH7 |
CH6 |
CH5 |
ISET |
CH4 |
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` Suitable for use in SnPb or Pb-free soldering processes. |
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WQFN-24L 4x4 |
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www.richtek.com
1
RT8562
Typical Application Circuit
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VOUT |
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L |
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D1 |
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40V MAX |
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VIN |
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10µH |
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6V to 24V |
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C1 |
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C5 |
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R4 |
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10µF |
RT8562 |
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10µF |
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10 |
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10 LED String |
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23 VIN |
LX1 |
19 |
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C6 |
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R7 |
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LX2 |
20 |
C7 |
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1µF |
R5 |
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15 |
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5V |
1k |
1 EN |
CH1 |
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R6 1k |
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6 PWM |
CH2 |
14 |
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... |
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8 |
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PWM Signal |
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CH7 |
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22 COMP |
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CH8 |
7 |
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R2 |
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R1 |
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24 |
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16 |
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VDC |
OVP |
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VOUT |
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1.8k |
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C2 |
C3 |
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3 SS |
ISET |
11 |
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R3 |
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4.7µF |
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GND |
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RISET |
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3.9nF |
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C4 |
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0.1µF |
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5, Exposed Pad (25) |
4.75k |
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ILED (mA) = |
20 x 4.75 |
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RISET (kΩ) |
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Figure 1. 1MHz, 20mA Full Scale Current PWM Dimming Control |
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VOUT |
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L |
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D1 |
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40V MAX |
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VIN |
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10µH |
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6V to 24V |
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C1 |
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C5 |
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R4 |
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10µF |
RT8562 |
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10µF |
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10 |
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10 LED String |
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23 VIN |
LX1 |
19 |
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... : |
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C6 |
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LX2 |
20 |
R7 |
C7 |
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1µF |
R5 |
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15 |
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5V |
1k |
1 EN |
CH1 |
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Analog |
R6 1k |
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6 PWM |
CH2 |
14 |
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... |
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8 |
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CH7 |
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Dimming |
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22 COMP |
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CH8 |
7 |
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R2 |
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R1 |
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24 |
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16 |
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VDC |
OVP |
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VOUT |
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1.8k |
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C2 |
C3 |
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3 SS |
ISET |
11 |
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R3 |
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4.7µF |
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GND |
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RISET |
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3.9nF |
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C4 |
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5, Exposed Pad (25) |
4.75k |
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0.1µF |
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ILED (mA) = |
20 x 4.75 |
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RISET (kΩ) |
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Figure 2. 1MHz, 20mA Full Scale Current Analog Dimming Control
www.richtek.com |
DS8562-01 April 2011 |
2
RT8562
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VOUT |
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L |
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D1 |
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40V MAX |
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VIN |
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10µH |
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4V to 36V |
C7 |
C1 |
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C5 |
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1µF |
10µF |
RT8562 |
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10µF |
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R4 |
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19 |
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10 LED String |
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LX1 |
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... : |
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VAVDD |
10 |
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23 |
VIN |
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R7 |
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6V to 24V |
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C6 |
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LX2 |
20 |
C8 |
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R5 |
2.2µF |
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CH1 |
15 |
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5V |
1k |
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1 EN |
CH2 |
14 |
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... |
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R6 1k |
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Analog |
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6 PWM |
CH7 |
8 |
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Dimming |
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22 COMP |
CH8 |
7 |
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R2 |
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R1 |
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24 VDC |
OVP |
16 |
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VOUT |
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1.8k |
C3 |
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3 SS |
ISET |
11 |
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C2 |
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R3 |
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4.7µF |
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GND |
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RISET |
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3.9nF |
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C4 |
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5, Exposed Pad (25) |
4.75k |
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0.1µF |
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ILED (mA) = |
20 x 4.75 |
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Note : |
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RISET (kΩ) |
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1.Due to the limitaion of maximum duty, 5V input can support typically to VOUT = 33V.
2.Due to the limitaion of maximum duty, 4V input can support typically to VOUT = 26V.
Figure 3. Wide Range VIN Application by Connecting VCC Pin to LCD Driver Power AVDD
Function Block Diagram
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LX1, LX2 |
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VIN |
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OSC |
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CH1 |
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5.6V |
+ |
+ |
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R |
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OVP |
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- |
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R |
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1.2V |
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- |
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EN |
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+ - |
+ |
CH2 |
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1.6V |
+ |
Shutdown |
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5V |
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- |
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VDC |
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LDO |
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VOUT |
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COMP |
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Regulation |
+ |
CH7 |
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Unit |
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- |
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5uA |
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5V |
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SS |
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+ |
CH8 |
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PWM |
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- |
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- |
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ISET |
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DS8562-01 |
April |
2011 |
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www.richtek.com |
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3 |
RT8562
Functional Pin Description
Pin No. |
Pin Name |
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Pin Function |
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1 |
EN |
Chip enable pin, when pulled low, chip is in shutdown mode. |
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2, 4, 21 |
NC |
No Internal Connection. |
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3 |
SS |
Soft Start Pin, a capacitor of at least 10nF is required for soft start. |
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5, |
GND |
Ground pin of the chip. The exposed pad must be soldered to a large PCB and |
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25 (Exposed Pad) |
connected to GND for maximum power dissipation. |
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Analog/Digital dimming control. When using analog dimming, |
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6 |
PWM |
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20 x 4.75 |
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ILED (mA) = |
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for VPWM ≥ 1.2V. |
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RISET(kΩ) |
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11 |
ISET |
A resistor or a current from DAC on this pin programs the full LED current. |
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10, 9, 8, 7 |
CH5 to CH8 |
Channel 5 to Channel 8 LED current sink. Leave the pin unconnected if not used. |
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15, 14, 13, 12 |
CH1 to CH4 |
Channel 1 to Channel 4 LED current sink. Leave the pin unconnected if not used. |
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16 |
OVP |
Over Voltage Protection. PWM boost converter turns off when VOVP goes |
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higher than 1.2V. |
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17, 18 |
PGND1, |
Power Ground (LX1/LX2 power return). |
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PGND2 |
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19, 20 |
LX1, LX2 |
PWM boost converter switch node. |
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22 |
COMP |
PWM boost converter loop compensation node. |
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23 |
VIN |
Power supply of the chip. For good bypass, a low ESR capacitor is required. |
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24 |
VDC |
Put 1μF capacitor on this pin to stabilize the 5V output of the internal regulator. |
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This regulator is for chip internal use only. |
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Absolute Maximum Ratings (Note 1)
z Supply Voltage, VIN ------------------------------------------------------------------------------------------------------ |
28V |
z LX1, LX2 Pin Voltage at Switching Off -------------------------------------------------------------------------------- |
45V |
z CH1 to CH8 Pin ------------------------------------------------------------------------------------------------------------ |
35V |
z PWM, EN, OVP Pin Voltage ------------------------------------------------------------------------------------------- |
−0.3V to 5.5V |
z Power Dissipation, PD @ TA = 25°C |
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WQFN-24L 4x4 ------------------------------------------------------------------------------------------------------------ |
1.923W |
z Package Thermal Resistance (Note 2) |
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WQFN-24L 4x4, θJA ------------------------------------------------------------------------------------------------------- |
52°C/W |
WQFN-24L 4x4, θJC ------------------------------------------------------------------------------------------------------ |
7°C/W |
z Junction Temperature ----------------------------------------------------------------------------------------------------- |
150°C |
z Lead Temperature (Soldering, 10 sec.) ------------------------------------------------------------------------------- |
260°C |
z Storage Temperature Range -------------------------------------------------------------------------------------------- |
−65°C to 150°C |
z ESD Susceptibility (Note 3) |
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HBM (Human Body Mode) ---------------------------------------------------------------------------------------------- |
2kV |
MM (Machine Mode) ------------------------------------------------------------------------------------------------------ |
200V |
Recommended Operating Conditions |
(Note 4) |
z Supply Input Voltage, VIN ----------------------------------------------------------------------------------------------- |
6V to 24V |
z Junction Temperature Range -------------------------------------------------------------------------------------------- |
−40°C to 125°C |
z Ambient Temperature Range -------------------------------------------------------------------------------------------- |
−40°C to 85°C |
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www.richtek.com |
DS8562-01 April 2011 |
4