Richtek RT8560AGQW Schematic [ru]
RT8560A
High Voltage 4 Channel LED Driver
General Description
The RT8560A is a 60V 4-channel LED driver capable of delivering 30mA to each channel with 15 LEDs (3.6V per diode) total 60 LEDs with one driver. The RT8560A is a current mode boost converter opearated at 1MHz switching frequency, wide VIN range covers from 6V to 40V and the on-chip current switch is rated at 1.5A.
The PWM output voltage loop selects and regulates the LED pin with the highest voltage string to 0.9V allowing voltage mismatches between LED strings. The RT8560A automatically detects and disconnects any unconnected and/or broken strings during operation from PWM loop to prevent VOUT from over voltage.
The 3% matched LED currents on all channels are simply programmed with a resistor or a current sink. Both analog dimming and digitally controlled PWM dimming are supported by RT8560A. Analog dimming is linearly controlled by an external voltage. With an on-chip output clampping amplifier and a 200kΩ resistor, PWM dimming signal is easily low-pass filtered to an analog dimming signal with one external capacitor for noise-free PWM dimming. A very high contrast ratio true digital PWM dimming can be achieved by driving EN pin to PWM shutdown the chip or by driving ACTL pin.
Other protecting features include programmable PWM output over voltage protection, LED curren limit, PWM switch current limit and thermal shutdown. The RT8560A is packaged with a tiny footprint package of WQFN-20L 4x4 packages.
Pin Configurations
(TOP VIEW)
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GND |
GND |
LED1 |
LED2 |
LED3 |
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20 |
19 |
18 |
17 |
16 |
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GND |
1 |
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15 |
LED4 |
GND |
2 |
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14 |
VC |
GND |
3 |
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GND |
13 |
SS |
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SW |
4 |
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21 |
12 |
OVP |
SW |
5 |
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11 |
EN |
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6 |
7 |
8 |
9 |
10 |
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VCC2 |
VCC1 |
RISET |
ACTL |
DCTL |
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WQFN-20L 4x4 |
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Features
zHigh Voltage : VIN up to 40V, VOUT up to 60V, Driving up to 60 x 3.6V LEDs (15 each channel)
zChannel Current Programmabe 4mA to 30mA and Matched to 3% Accuracy
zCurrent Mode PWM 1MHz Boost Converter
zEasy Analog and Digital Dimming Control
zProgrammable Soft Start
zAutomatic Detecting Unconnected and/or Broken Channel
zProgrammable Over Voltage Protection
zDisconnects LED in Digital Dimming : Providing High Accuracy Digital Dimming by PWM at ACTL Pin or EN Pin
zVIN Under Voltage Lockout
zOver Temperature Protection
zCurrent Limiting Protection
zSmall 20-Lead WQFN Package
zRoHS Compliant and Halogen Free
Applications
zUMPC and Notebook Computer Backlight
zGPS, Portable DVD Backlight
zDesk Lights and Room Lighting
Ordering Information
RT8560A 
Package Type
QW : WQFN-20L 4x4 (W-Type)
Lead Plating System
G : Green (Halogen Free and Pb Free)
Note :
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.
DS8560A-01 April 2011 |
www.richtek.com |
1
RT8560A
Typical Application Circuit
VIN |
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COUT3 |
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6V to 40V |
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1µF |
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VOUT |
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L |
D |
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60V MAX |
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10µH |
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CVIN |
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15 LED String |
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10µF |
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RVCC1 |
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RT8560A |
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COUT1 COUT2 |
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R4 |
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10 |
C2 |
4, 5 SW |
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18 |
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7 VCC1 |
LED1 |
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CVCC1 |
R3 |
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LED2 |
17 |
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1µF |
5V |
1k |
11 EN |
LED3 |
16 |
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VOUT |
R1 |
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12 OVP |
LED4 |
15 |
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RISET |
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5.36k |
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ILED = 20mA × |
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R2 |
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RISET |
8 |
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5.36k |
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RVCC2 |
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RISET |
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R5 |
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VIN |
10 |
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6 VCC2 |
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ACTL |
9 |
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1k |
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CVCC2 |
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PWM Signal |
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1µF |
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DCTL |
10 |
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14 VC |
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GND 1, 2, 3, 19, 20, Exposed Pad (21) |
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RVC |
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13 SS |
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1.8k |
C1 |
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CVC |
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0.1µF |
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3.9nF |
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Figure 1. 1MHz, 20mA Full Scale Current Digital PWM Dimming Control
VIN |
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COUT3 |
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6V to 40V |
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1µF |
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VOUT |
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L |
D |
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60V MAX |
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10µH |
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CVIN |
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15 LED String |
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10µF |
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RVCC1 |
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RT8560A |
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COUT1 COUT2 |
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R4 |
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10 |
C2 |
4, 5 SW |
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18 |
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7 VCC1 |
LED1 |
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CVCC1 |
R3 |
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LED2 |
17 |
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1µF |
5V |
1k |
11 EN |
LED3 |
16 |
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VOUT |
R1 |
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12 OVP |
LED4 |
15 |
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RISET |
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ILED = 20mA × |
5.36k |
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R2 |
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RISET |
8 |
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5.36k |
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RVCC2 |
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RISET |
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VIN |
10 |
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6 VCC2 |
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R5 |
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Analog |
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CVCC2 |
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ACTL |
9 |
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1k |
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Dimming |
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1µF |
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DCTL |
10 |
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14 VC |
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GND 1, 2, 3, 19, 20, Exposed Pad (21) |
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RVC |
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13 SS |
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1.8k |
C1 |
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CVC |
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0.1µF |
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3.9nF |
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Figure 2. 1MHz, 20mA Full Scale Current Analog Dimming Control
www.richtek.com |
DS8560A-01 April 2011 |
2
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RT8560A |
VIN |
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COUT3 |
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6V to 40V |
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1µF |
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VOUT |
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L |
D |
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60V MAX |
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10µH |
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CVIN |
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15 LED String |
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10µF |
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RVCC1 |
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RT8560A |
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COUT1 COUT2 |
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R4 |
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10 |
C3 |
4, 5 SW |
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18 |
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7 VCC1 |
LED1 |
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CVCC1 |
R3 |
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LED2 |
17 |
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1µF |
5V |
1k |
11 EN |
LED3 |
16 |
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VOUT |
R1 |
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12 OVP |
LED4 |
15 |
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RISET |
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5.36k |
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ILED = 20mA × |
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R2 |
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RISET |
8 |
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5.36k |
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RVCC2 |
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RISET |
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VIN |
10 |
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6 VCC2 |
ACTL |
9 |
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R5 |
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C2 |
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CVCC2 |
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DCTL |
10 |
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1k |
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0.1µF |
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1µF |
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PWM Signal |
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14 VC |
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GND 1, 2, 3, 19, 20, Exposed Pad (21) |
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RVC |
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13 SS |
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1.8k |
C1 |
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CVC |
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0.1µF |
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3.9nF |
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Figure 3. 1MHz, 20mA Full Scale Current PWM to Analog Dimming Control
VIN |
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4V to 40V |
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COUT3 |
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1µF |
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VOUT |
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VAVDD |
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L |
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60V MAX |
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6V to 40V |
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D |
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10µH |
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CVIN |
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15 LED String |
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10µF |
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RVCC1 |
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COUT1 |
COUT2 |
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RT8560A |
: |
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10 |
C2 |
R4 |
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4, 5 SW |
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LED1 18 |
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7 VCC1 |
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CVCC1 |
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R3 |
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LED2 17 |
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2.2µF |
5V |
1k |
11 EN |
LED3 16 |
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V |
R1 |
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12 |
OVP |
LED4 15 |
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RISET |
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5.36k |
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ILED = 20mA × |
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OUT |
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R2 |
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RISET 8 |
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5.36k |
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RISET |
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RVCC2 |
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R5 |
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10 |
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6 VCC2 |
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ACTL 9 |
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1k |
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VIN |
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CVCC2 |
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DCTL 10 |
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PWM Signal |
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1µF |
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14 VC |
GND 1, 2, 3, 19, 20, Exposed Pad (21) |
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RVC |
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13 SS |
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1.8k |
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C1 |
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CVC |
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0.1µF |
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3.9nF |
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Figure 4. Wide Range VINApplication by Connecting VCC1 to LCDDriver Power AVDD
DS8560A-01 April 2011 |
www.richtek.com |
3
RT8560A
Function Block Diagram
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SW |
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VCC1 |
- |
OSC |
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S |
LED1 |
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6.2V |
+ |
+ |
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R |
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OVP |
+ |
- |
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R |
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2.5V |
- |
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+ - |
LED2 |
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- |
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EN |
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+ |
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2V |
+ |
Shutdown |
- |
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VCC2 |
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VC |
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VOUT |
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Regulation |
LED3 |
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Unit |
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+ |
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- |
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6uA |
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5V |
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SS |
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LED4 |
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1.2V |
1.2V |
+ |
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DCTL |
+ |
- |
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200k |
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- |
+ |
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- |
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ACTL |
RISET |
www.richtek.com |
DS8560A-01 April 2011 |
4
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RT8560A |
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Functional Pin Description |
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Pin Number |
Pin Name |
Pin Function |
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1, 2, 3, 19, 20, |
GND |
Ground pin of the chip. The exposed pad must be soldered to a large PCB |
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21 (Exposed Pad) |
and connected to GND for maximum power dissipation. |
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4, 5 |
SW |
PWM boost converter switch node. |
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Bipolar power switch base current supply. Typical beta of the power NPN |
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6 |
VCC2 |
switch is approximately 70. VCC2 can be connected either to VCC1 or to a |
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separate lower voltage, as low as 3V, for better system efficiency and/or |
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heat concern. A good bypass is necessary. |
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7 |
VCC1 |
Power supply of the chip. For good bypass, a low ESR capacitor is required. |
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8 |
RISET |
A resistor or a current from DAC on this pin programs the full LED current. |
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9 |
ACTL |
Analog/Digital dimming control. When using analog dimming, |
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ILED = 20mA × 5.36k for VACTL ≥ 1.2V. |
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RISET |
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By adding a 0.1uF filtering capacitor on ACTL pin, the PWM dimming signal |
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10 |
DCTL |
on DCTL pin will be averaged out and converted into analog dimming signal |
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on ACTL pin. |
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11 |
EN |
Chip enable pin, when low chip is in shutdown mode. |
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12 |
OVP |
Over voltage protection. PWM boost converter turns off when VOVP goes |
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higher than 2.5V. |
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13 |
SS |
Soft start pin, a capacitor of at least 10nF is required for soft start. |
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14 |
VC |
PWM boost converter loop compensation node. |
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18, 17, 16, 15 |
LED1, LED2, |
Channel 1 to Channel 4 LED current sink. Leave the pin unconnected if not |
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LED3, LED4 |
used. |
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DS8560A-01 April 2011 |
www.richtek.com |
5
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