Richtek RT8560AGQW Schematic [ru]
High Voltage 4 Channel LED Driver
RT8560A
General Description
The RT8560A is a 60V 4-channel LED driver capable of
delivering 30mA to ea ch cha nnel with 15 LEDs (3.6V per
diode) total 60 LEDs with one driver. The R T8560A is a
current mode boost converter opearated at 1MHz switching
frequency , wide V
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 a ny unconnected
and/or broken strings during operation from PWM loop to
prevent V
OUT
The 3% matched LED currents on all cha nnels are simply
programmed with a resistor or a current sink. Both a nalog
dimming and digitally controlled PWM dimming are
supported by RT8560A. Analog dimming is linearly
controlled by an external voltage. With a n on-chip output
clampping a mplifier a nd 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.
range covers from 6V to 40V and the
IN
from over voltage.
Features
zz
High V oltage : VIN up to 40V , V
z
zz
up to 60V , Driving
OUT
up to 60 x 3.6V LEDs (15 each channel)
zz
z Channel Current Programmabe 4mA to 30mA and
zz
Matched to 3% Accuracy
zz
z Current Mode PWM 1MHz Boost Converter
zz
zz
z Easy Analog and Digital Dimming Control
zz
zz
z Programmable Soft Start
zz
zz
z Automatic Detecting Unconnected and/or Broken
zz
Channel
zz
z Programmable Over Voltage Protection
zz
zz
z Disconnects LED in Digital Dimming : Providing
zz
High Accuracy Digital Dimming by PWM at ACTL
Pin or EN Pin
zz
z V
Under Voltage Lockout
zz
IN
zz
z Over Temperature Protection
zz
zz
z Current Limiting Protection
zz
zz
z Small 20-Lead WQFN Package
zz
zz
z RoHS Compliant and Halogen Free
zz
Applications
z UMPC and Notebook Computer Backlight
z GPS, Portable DVD Backlight
z Desk Lights and Room Lighting
Other protecting features include programmable PWM
output over voltage protection, LED curren limit, PWM
switch current limit and thermal shutdown. The R T8560A
is packaged with a tiny footprint package of WQFN-20L
4x4 packages.
Ordering Information
RT8560A
Package Type
QW : WQFN-20L 4x4 (W-Type)
Lead Plating System
G : Green (Halogen Free and Pb Free)
Note :
Pin Configurations
(TOP VIEW)
GND
GND
20 19 18 1617
1
GND
2
GND
3
GND
SW
SW
GND
4
5
7
8910
6
VCC2
VCC1
LED2
LED1
21
ACTL
RISET
LED3
15
LED4
14
VC
13
SS
12
OVP
11
EN
DCTL
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.
Marking Information
For marking information, contact our sales representative
directly or through a Richtek distributor located in your
area.
WQFN-20L 4x4
DS8560A-01 April 2011 www.richtek.com
1
RT8560A
Typical Application Circuit
V
IN
6V to 40V
L
10µH
C
VIN
10µF
R
VCC1
10
C
1µF
V
OUT
V
IN
VCC1
R
R
1.8k
VCC2
10
VC
C
VC
3.9nF
C2
R1
5V
R4
C
VCC2
1µF
R3
1k
C
OUT3
1µF
R2
C1
0.1µF
4, 5
11
12
14
13
7
6
D
SW
VCC1
EN
OVP
VCC2
VC
SS
15 LED String
RT8560A
V
OUT
60V MAX
:
:
:
:
:
:
:
:
:
:
:
:
18
LED1
17
LED2
16
LED3
15
LED4
RISET
ACTL
DCTL
GND
R
ISET
5.36k
8
R5
1k
9
10
PWM Signal
1, 2, 3, 19, 20, Exposed Pad (21)
:
:
C
OUT1
:
:
I = 20mAR×
LED
C
OUT2
5.36k
ISET
Figure 1. 1MHz, 20mA Full Scale Current Digital PWM Di mming Control
V
IN
6V to 40V
R
10
C
1µF
V
OUT
V
IN
VCC1
VCC1
R
VCC2
10
R
VC
1.8k
C
VC
3.9nF
C2
5V
R1
10µH
C
VIN
10µF
L
R4
C
VCC2
1µF
R3
1k
R2
C
OUT3
1µF
4, 5
C1
0.1µF
11
12
14
13
7
6
D
SW
VCC1
EN
OVP
VCC2
VC
SS
15 LED String
RT8560A
V
OUT
60V MAX
:
:
:
:
:
:
:
:
:
:
:
:
18
LED1
17
LED2
16
LED3
15
LED4
RISET
ACTL
DCTL
GND
R
ISET
5.36k
8
R5
9
1k
10
1, 2, 3, 19, 20, Exposed Pad (21)
:
:
C
OUT1
:
:
I = 20mAR×
LED
Analog
Dimming
C
OUT2
5.36k
ISET
Figure 2. 1MHz, 20mA Full Scale Current An alog Dimming Control
DS8560A-01 April 2011www.richtek.com
2
V
IN
6V to 40V
R
10
C
1µF
V
OUT
V
IN
VCC1
VCC1
R
VCC2
10
R
VC
1.8k
C
3.9nF
VC
C3
5V
R1
10µH
C
VIN
10µF
L
R4
C
1µF
C
R3
1k
R2
VCC2
C1
0.1µF
OUT3
1µF
4, 5
11
12
14
13
7
6
D
SW
VCC1
EN
OVP
VCC2
VC
SS
15 LED String
RT8560A
V
OUT
60V MAX
:
:
:
:
:
:
:
:
:
:
:
:
18
LED1
17
LED2
16
LED3
15
LED4
RISET
ACTL
DCTL
8
9
10
R
ISET
5.36k
R5
1k
PWM Signal
1, 2, 3, 19, 20, Exposed Pad (21)
GND
:
:
C
OUT1
:
:
I = 20mAR×
LED
C
RT8560A
OUT2
5.36k
ISET
C2
0.1µF
Figure 3. 1MHz, 20mA Full Scale Current PWM to Analog Di mming Control
V
IN
V
AVDD
6V to 40V
R
10
V
OUT
V
IN
VCC1
C
VCC1
2.2µF
R
4V to 40V
C2
5V
R1
VCC2
10
R
VC
1.8k
C
VC
3.9nF
10µH
C
VIN
10µF
L
R4
C
VCC2
1µF
C
R3
1k
R2
C1
0.1µF
OUT3
1µF
4, 5
11
12
14
13
7
6
D
SW
VCC1
EN
OVP
VCC2
VC
SS
15 LED String
RT8560A
V
OUT
60V MAX
:
:
:
:
:
:
:
:
:
:
:
:
18
LED1
17
LED2
16
LED3
15
LED4
RISET
ACTL
DCTL
GND
R
ISET
5.36k
8
R5
1k
9
10
1, 2, 3, 19, 20, Exposed Pad (21)
:
:
C
OUT1
:
:
I = 20mAR×
LED
PWM Signal
C
OUT2
5.36k
ISET
Figure 4. Wide Range VIN Application by Connecting VCC1 to LCD Driver Power A V DD
DS8560A-01 April 2011 www.richtek.com
3
RT8560A
Function Block Diagram
SW
VCC1
OVP
EN
VCC2
VC
SS
DCTL
6.2V
2.5V
2V
6uA
+
+
-
+
1.2V
+
-
OSC
Shutdown
200k
S
R
R
+
-
V
OUT
Regulation
Unit
1.2V
+
-
+
LED1
-
LED2
+
-
LED3
+
-
5V
LED4
+
-
ACTL
RISET
DS8560A-01 April 2011www.richtek.com
4
Functional Pin Description
Pin Numbe r Pin Name Pin Function
1, 2, 3, 19, 20,
21 (Exposed Pad)
4, 5 SW
6 VCC2
7 VCC1
8 RISET
GND
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 N PN
switch is approximately 70. VCC2 can be connected either to VCC1 or to a
separate lower voltage, as low as 3V, for better s ystem 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.
RT8560A
9 ACTL
10 DCTL
11 EN
12 OVP
13 SS
14 VC
18, 17, 16, 15
LED1, LED2,
LED3, LED4
Analog / Digi tal dimming co ntrol. When using anal og dimming,
I = 20mA for V 1.2V.
LED ACTL
By adding a 0.1uF filtering capacitor on ACTL pin, the PWM dimming signal
on DCTL pin will be averaged out and converte d 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
higher than 2.5V.
Soft start pin, a capacitor of at least 10nF is requi red for soft start.
PWM boost converter loop compensation node.
Channel 1 to Channel 4 LED current sink. Leave the pin unconnected if not
used.
5.36k
×≥
R
ISET
OVP
goes
DS8560A-01 April 2011 www.richtek.com
5
Loading...