RT8560
High Voltage 4 Channel LED Driver
General Description
The RT8560 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 RT8560 is a
current mode boost converter opearated at 1MHz switching
frequency, wide V
IN
range covers from 7V 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 RT8560
automatically detects and disconnects any unconnected
and/or broken strings during operation from PWM loop to
prevent V
OUT
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 RT8560. 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 RT8560
is packaged with a tiny footprint package of WQFN-20L
4x4 packages.
Features
High Voltage : V
IN
up to 40V, V
OUT
up to 60V, Driving
up to 60 x 3.6V LEDs (15 each channel)
Channel Current Programmabe 4mA to 30mA and
Matched to 3% Accuracy
Current Mode PWM 1MHz Boost Converter
Easy Analog and Digital Dimming Control
Programmable Soft Start
Automatic Detecting Unconnected and/or Broken
Channel
Programmable Over Voltage Protection
Disconnects LED in Digital Dimming : Providing
High Accuracy Digital Dimming by PWM at ACTL
Pin or EN Pin
V
IN
Under Voltage Lockout
Over Temperature Protection
Current Limiting Protection
Small 20-Lead WQFN Package
RoHS Compliant and Halogen Free
Applications
UMPC and Notebook Computer Backlight
GPS, Portable DVD Backlight
Desk Lights and Room Lighting
Ordering Information
RT8560
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 require-
ments of IPC/JEDEC J-STD-020.
Suitable for use in SnPb or Pb-free soldering processes.
Pin Configurations
(TOP VIEW)
LED1
LED2
17
20 19 18
LED3
16
15
14
GND
GND
GND
GND
GND
SW
SW
1
2
3
4
5
6
7
8
9
10
GND
21
13
12
11
LED4
VC
SS
OVP
EN
Marking Information
For marking information, contact our sales representative
directly or through a Richtek distributor located in your
area.
VCC2
WQFN-20L 4x4
DS8560-01 April 2011
www.richtek.com
1
RISET
VCC1
ACTL
DCTL
RT8560
Typical Application Circuit
V
IN
7V to 40V
L
10µH
C
VIN
10µF
R
VCC1
10
C2
R4
4, 5 SW
7 VCC1
C
VCC1
1µF
V
OUT
5V
R1
R2
V
IN
R
VCC2
10
C
VCC2
1µF
14
R
VC
1.8k
C
VC
3.9nF
VC
13 SS
C1
0.1µF
6 VCC2
R3
1k
11 EN
12
OVP
RISET
8
LED1
18
LED2 17
LED3 16
LED4 15
R
ISET
5.36k
R5
1k
PWM Signal
I
LED
= 20mA
×
5.36k
R
ISET
C
OUT3
1µF
D
15 LED String
RT8560
:
:
:
:
V
OUT
60V MAX
:
:
:
:
:
:
:
:
:
:
:
:
C
OUT1
C
OUT2
ACTL 9
DCTL 10
GND
1, 2, 3, 19, 20, Exposed Pad (21)
Figure 1. 1MHz, 20mA Full Scale Current Digital PWM Dimming Control
V
IN
7V to 40V
L
10µH
C
VIN
10µF
R
VCC1
10
C2
R4
4, 5 SW
7 VCC1
C
VCC1
1µF
V
OUT
5V
R1
R2
V
IN
R
VCC2
10
C
VCC2
1µF
14
R
VC
1.8k
C
VC
3.9nF
VC
13 SS
C1
0.1µF
6 VCC2
ACTL 9
DCTL 10
GND
R3
1k
11 EN
12
OVP
LED1
18
LED2 17
LED3 16
LED4 15
RISET
8
R
ISET
5.36k
I
LED
= 20mA
×
5.36k
R
ISET
C
OUT3
1µF
D
15 LED String
RT8560
:
:
:
:
V
OUT
60V MAX
:
:
:
:
:
:
:
:
:
:
:
:
C
OUT1
C
OUT2
R5
1k
Analog
Dimming
1, 2, 3, 19, 20, Exposed Pad (21)
Figure 2. 1MHz, 20mA Full Scale Current Analog Dimming Control
www.richtek.com
2
DS8560-01 April 2011
RT8560
V
IN
7V to 40V
L
10µH
C
VIN
10µF
R
VCC1
10
C3
R4
4, 5 SW
7 VCC1
C
VCC1
1µF
V
OUT
5V
R1
R2
V
IN
R
VCC2
10
C
VCC2
1µF
14 VC
13 SS
C1
0.1µF
6 VCC2
R3
1k
11 EN
12
OVP
LED1
18
LED2 17
LED3 16
LED4 15
RISET
8
R
ISET
5.36k
I
LED
= 20mA
×
5.36k
R
ISET
C
OUT3
1µF
D
15 LED String
RT8560
:
:
:
:
V
OUT
60V MAX
:
:
:
:
:
:
:
:
:
:
:
:
C
OUT1
C
OUT2
ACTL 9
DCTL 10
R5
1k
PWM Signal
C2
0.1µF
R
VC
1.8k
C
VC
3.9nF
GND
1, 2, 3, 19, 20, Exposed Pad (21)
Figure 3. 1MHz, 20mA Full Scale Current PWM to Analog Dimming Control
V
IN
4V to 40V
C
OUT3
1µF
V
AVDD
7V to 40V
L
10µH
C
VIN
10µF
R
VCC1
10
C2
R4
D
15 LED String
RT8560
4, 5
SW
LED1
18
LED2 17
LED3 16
LED4 15
OVP
RISET
6 VCC2
C
VCC2
1µF
14
R
VC
1.8k
C
VC
3.9nF
VC
13 SS
C1
0.1µF
8
R
ISET
5.36k
R5
1k
PWM Signal
I
LED
= 20mA
×
5.36k
R
ISET
:
:
:
:
V
OUT
60V MAX
:
:
:
:
:
:
:
:
:
:
:
:
C
OUT1
C
OUT2
7 VCC1
C
VCC1
2.2µF
V
OUT
5V
R1
R2
V
IN
R
VCC2
10
R3
1k
11 EN
12
ACTL 9
DCTL 10
GND
1, 2, 3, 19, 20, Exposed Pad (21)
Figure 4. Wide Range VIN Application by Connecting VCC1 to LCD Driver Power AVDD
DS8560-01 April 2011
www.richtek.com
3
RT8560
Functional Pin Description
Pin Number
1, 2, 3, 19, 20,
21 (Exposed Pad)
4, 5
Pin Name
GND
SW
Pin Function
Ground pin of the chip.
The exposed pad must be soldered to a large PCB
and connected to GND for maximum power dissipation.
PWM boost converter switch node.
Bipolar power switch base current supply. Typical beta of the power NPN
6
VCC2
switch is approximately 70. VCC2 can be connected either to VCC1 or to a
separate lower voltage, as low as 3V, for better system efficiency and/or
heat concern. A good bypass is necessary.
Power supply of the chip. For good bypass, a low ESR capacitor is required.
A resistor or a current from DAC on this pin programs the full LED current.
Analog/Digital dimming control. When using analog dimming,
I
LED
= 20mA
×
5.36k for V
ACT L
≥
1.2V.
R
ISET
By adding a 0.1uF filtering capacitor on ACTL pin, the PWM dimming signal
on DCTL pin will be averaged out and converted into analog dimming signal
on ACTL pin.
Chip enable pin, when low chip is in shutdown mode.
Over voltage protection. PWM boost converter turns off when V
OVP
goes
higher than 2.5V.
13
14
18, 17, 16, 15
SS
VC
LED1, LED2,
LED3, LED4
Soft start pin, a capacitor of at least 10nF is required for soft start.
PWM boost converter loop compensation node.
Channel 1 to Channel 4 LED current sink. Leave the pin unconnected if not
used.
7
8
9
VCC1
RISET
ACTL
10
11
12
DCTL
EN
OVP
DS8560-01 April 2011
www.richtek.com
5
Embedded System
京公网安备 11010802033920号
EEWORLD
