Richtek RT8561AGQW Schematic [ru]
®
High Voltage 8-CH LED Driver
RT8561A
General Description
The RT8561A is a 40V 8-CH LED driver capable of delivering
30mA to each channel with 10 LEDs (3.6V per diode),
total of 80 LEDs with one driver. The RT8561A is a current
mode boost converter operated at 1MHz, wide VIN range
covers from 6V to 24V and the on-chip current switch is
rated at 2.5A.
The PWM output voltage loop regulates the LED pins to
0.6V with an auto-adjustment circuit allowing voltage
mismatches between LED strings. The RT8561A automati-
cally detects and disconnects any unconnected and/or
broken strings during operation from PWM loop to prevent
V
from over voltage.
OUT
The 1.5% 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 the RT8561A. Analog dimming is linearly
controlled by an external voltage. With an on-chip output
clamping amplifier and a 300kΩ 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 ACTL pin with a PWM
signal.
Other protecting features include programmable output
over voltage protection, LED current limit, PWM switch
current limit and thermal shutdown.
The RT8561A is packaged with a tiny footprint package of
WQFN-24L 4x4 packages.
Ordering Information
RT8561A
Package Type
QW : WQFN-24L 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.
Features
z High V oltage : V
up to 80 x 3.6V LEDs (10 each channel)
z Channel Current Progra mmable 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
at ACTL Pin
z V
Under Voltage Lockout
IN
zz
z Over Temperature Protection
zz
zz
z Current Limiting Protection
zz
zz
z Small 24-Lead WQFN Package
zz
zz
z RoHS Compliant and Halogen Free
zz
up to 24V , V
IN
up to 40V , Driving
OUT
Applications
z UMPC and Notebook Computer Backlight
z GPS, Portable DVD Backlight
z Desk Lights and Room Lighting
Pin Configurations
(TOP VIEW)
SW
21 20 19
25
11
ACTL
RISET GND
SW
18
17
16
15
14
13
DCTL
VCC
CREG
LED8
LED7
LED6
EN
LED1
LED2
LED3
LED4
LED5
OVP
GND
GND
GND
24 2223
1
2
3
4
5
6
GND
7
8910 12
SS
VC
NC
WQFN-24L 4x4
Marking Information
CZ= : Product Code
CZ=YM
DNN
YMDNN : Date Code
Copyright 2012 Richtek Technology Corporation. All rights reserved. is a registered trademark of Richtek Technology Corporation.
©
DS8561A-02 April 2012 www.richtek.com
1
RT8561A
Typical Application Circuit
V
IN
6V to 24V
R
10
VIN1
C
VIN1
2.2µF
V
OUT
4.7µF
0.1µF
10µH
C
VIN1
10µF
5V
R1
L
R2
R
VC
1.8k
C
VC
3.9nF
1k
19, 20
18
13
17
12
D
6
9
7
SW
VCC
EN
OVP
CREG
SS
VC
DCTL
C
OUT
10µF
RT8561A
V
OUT
40V MAX
:
:
...
:
:
:
:
:
:
.
LED1
LED2
:
:
:
:
1
2
.
.
15
LED7
16
LED8
RISET
GND
ACTL
R
ISET
4.75k
10
21, 22, 23, 24, 25 (Exposed Pad)
1k
11
PWM Signal
:
:
10 LED String
:
:
LED
I
(mA) =
20 x 4.75
Ω)
R(k
ISET
Figure 1. 1MHz, 20mA Full Scale Current PWM Dimming Control
V
IN
6V to 24V
R
10
VIN1
C
VIN1
2.2uF
V
OUT
4.7µF
0.1µF
10µH
C
VIN1
10µF
5V
R1
R
1.8k
C
3.9nF
L
R2
VC
VC
D
19, 20
SW
18
VCC
1k
13
EN
6
OVP
17
CREG
9
SS
7
VC
12
DCTL
DCTL can be floating or
connected to ACTL
C
OUT
10µF
RT8561A
1
LED1
2
LED2
15
LED7
16
LED8
10
RISET
21, 22, 23, 24, 25 (Exposed Pad)
GND
11
ACTL
:
:
:
:
.
.
.
1k
40V MAX
:
...
:
:
:
R
ISET
4.75k
V
OUT
:
:
:
:
:
:
10 LED String
:
:
LED
I
(mA) =
Analog
Dimming
20 x 4.75
Ω)
R(k
ISET
Figure 2. 1MHz, 20mA Full Scale Current Analog Dimming Control
Copyright 2012 Richtek Technology Corporation. All rights reserved. is a registered trademark of Richtek Technology Corporation.
2
©
DS8561A-02 April 2012www.richtek.com
RT8561A
)
V
IN
6V to 24V
R
10
4.7µF
VIN1
C
VIN1
2.2µF
V
OUT
0.1µF
R
VC
1.8k
C
VC
3.9nF
L
10µH
C
VIN1
10µF
1k
5V
R1
R2
PWM Signal
19, 20
1k
18
13
6
17
9
7
12
D
SW
VCC
EN
OVP
CREG
SS
VC
DCTL
C
OUT
10µF
RT8561A
1
LED1
2
LED2
15
LED7
16
LED8
10
RISET
21, 22, 23, 24, 25 (Exposed Pad)
GND
11
ACTL
:
:
:
:
.
.
.
V
OUT
40V MAX
:
...
:
:
:
R
ISET
4.75k
:
:
:
:
10 LED String
:
:
:
:
LED
I
0.1µF
(mA) =
Figure 3. 1MHz, 20mA Full Scale Current PWM to Analog Dimming Control
20 x 4.75
Ω)
R(k
ISET
V
IN
V
AVDD
6V to 24V
R
10
C
2.2µF
VIN1
VIN1
4.7µF
4V to 36V
V
OUT
10µH
C
VIN1
10µF
5V
0.1µF
L
R1
R2
R
VC
1.8k
C
VC
3.9nF
1k
19, 20
18
13
17
12
D
6
9
7
SW
VCC
EN
OVP
CREG
SS
VC
DCTL
C
OUT
10µF
RT8561A
LED1
LED2
LED7
LED8
RISET
GND
ACTL
Note :
1. Due to the limitation of maximum duty 5V input can support typically to V
2. Due to the limitation of maximum duty 4V input can support typically to V
V
OUT
40V MAX
:
:
:
:
1
2
:
:
:
:
:
...
:
:
:
10 LED String
:
:
:
:
.
.
.
15
16
R
ISET
4.75k
10
21, 22, 23, 24, 25 (Exposed Pad)
11
PWM Signal
= 33V.
OUT
= 26V.
OUT
I
LED
(mA) =
20 x 4.75
R(k
ISET
Ω
Figure 4. Wide Range VIN Application by Connecting VCC Pin to LCD Driver Power AVDD
Copyright 2012 Richtek Technology Corporation. All rights reserved. is a registered trademark of Richtek Technology Corporation.
DS8561A-02 April 2012 www.richtek.com
©
3
RT8561A
Function Block Diagram
SW
VCC
OVP
EN
CREG
VC
SS
DCTL
5.6V
1.2V
1.6V
5V
LDO
5uA
+
+
-
+
1.2V
+
-
OSC
Shutdown
300k
+
-
V
Regulation
S
R
R
OUT
Unit
+
-
+
-
+
5V
+
-
-
+
-
LED1
LED2
LED7
LED8
ACTL
Copyright 2012 Richtek Technology Corporation. All rights reserved. is a registered trademark of Richtek Technology Corporation.
©
RISET
DS8561A-02 April 2012www.richtek.com
4
Functional Pin Description
Pin No. Pin Name Pin Function
LED1, LED2,
1, 2, 3, 4, 5
6 OVP
7 VC PWM boost converter loop compensation node.
8 NC No Internal Connection.
9 SS Soft Start Pin, a capacitor of at least 10nF is required for soft start.
10 RISET A resistor or a current from DAC on this pin programs the full LED current.
LED3, LED4,
LED5
Channel 1 to Channel 5 LED current sink. Leave the pin unconnected if not
used.
Over Voltage Protection. PWM boost converter turns off when V
higher than 1.2V.
RT8561A
goes
OVP
11 ACTL
12 DCTL
13 EN Chip enable pin, when pulled low, chip is in shutdown mode.
14, 15, 16
17 CREG
18 VCC Power supply of the chip. For good bypass, a low ESR capacitor is required.
19, 20 SW PWM boost converter switch node.
21, 22, 23, 24,
25 (Exposed Pad)
LED6, LED7,
LED8
GND
Analog/Digital dimming control. When using analog dimming,
I (mA) = for V 1.2V.
LED ACTL
By adding a 0.1μF filtering capacitor on the ACTL pin, the PWM dimming
signal on the DCTL pin will be averaged out and converted into analog
dimming signal on the ACTL pin.
Channel 6 to Channel 8 LED current sink. Leave the pin unconnected if not
used.
1μF capacitor should be placed on this pin to stabilize the 5V output of the
internal regulator. This regulator is for chip internal use only.
Ground pin of the chip. The exposed pad must be soldered to a large PCB
and connected to GND for maximum power dissipation.
20 x 4.75
R(kΩ)
ISET
≥
Copyright 2012 Richtek Technology Corporation. All rights reserved. is a registered trademark of Richtek Technology Corporation.
DS8561A-02 April 2012 www.richtek.com
©
5
RT8561A
Absolute Maximum Ratings (Note 1)
z Supply Voltage, VCC ----------------------------------------------------------------------------------------------------- −0.3V to 28V
z SW Pin Voltage at Switching Off -------------------------------------------------------------------------------------- −0.3V to 45V
z LED1 to LED8 Pin--------------------------------------------------------------------------------------------------------- −0.3V to 35V
z DCTL, ACTL, EN, OVP Pin Voltage ---------------------------------------------------------------------------------- −0.3V to 5.5V
z Power Dissipation, P
WQFN-24L 4x4 ------------------------------------------------------------------------------------------------------------ 1.923W
z Package Thermal Resistance (Note 2)
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)
HBM (Human Body Mode) ---------------------------------------------------------------------------------------------- 2kV
MM (Machine Mode) ------------------------------------------------------------------------------------------------------ 200V
Recommended Operating Conditions (Note 4)
@ TA = 25°C
D
z Supply Input Voltage, VCC ---------------------------------------------------------------------------------------------- 6V to 24V
z Junction Temperature Range --------------------------------------------------------------------------------------------
z Ambient Temperature Range --------------------------------------------------------------------------------------------
−40°C to 125°C
−40°C to 85°C
Electrical Characteristics
(VCC = 17V, T
Supply Current I
VIN Under Voltage Lockout
Threshold
Shutdown Current I
EN Threshold
Voltage
PWM Threshold
Voltage
EN Pin Input Current IEN VEN ≤ 5V -- -- 0.1 μA
LED Current Pro grammin g
LED Curr ent I
LEDs Curr ent Matching
RISET Pin Voltage V
Input Current of ACTL I
Copyright 2012 Richtek Technology Corporation. All rights reserved. is a registered trademark of Richtek Technology Corporation.
6
©
= 25°C, unless otherwise specified)
A
Parameter Symbol Test Conditions Min Typ Max Unit
VC ≤ 0.2V (Switching off) -- 3 5 mA
VCC
VIN Rising -- 5.6 5.95
V
Falling -- 4.9 --
IN
VEN ≤ 0.7V -- -- 10 μA
1.6 -- 5
-- -- 1
1.3 -- 5
-- -- 0.15
2V > V
V
ACTL
2V > V
V
ACTL
(I
(MAX)
3.6kΩ ≤ R
0.3V ≤ V
> 0.6V, R
LED
= 4.75kΩ,
ISET
> 1.2V
> 0.6V, R
LED
= 4.75kΩ,
ISET
> 1.2V, Calculating
− I
) / I
(MIN)
≤ 9.6k Ω, V
ISET
≤ 1.2V -- 1 2 μA
ACTL
Average
x 100%
ACTL
19 20 21 mA
-- -- 1.5 %
> 1.2V 1.17 1.2 1.23 V
DS8561A-02 April 2012www.richtek.com
Logic-High V
Logic-Low
Logic-High V
Logic-Low
V
UVLO
SHD N
EN_ H
V
EN_ L
PWM_H
V
PWM_L
LED
RISET
ACTL
V
V
V
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