LED Driver. RT8562B Datasheet

RT8562B Driver. Datasheet pdf. Equivalent

RT8562B Datasheet
Recommendation RT8562B Datasheet
Part RT8562B
Description High Voltage 8-CH LED Driver
Feature RT8562B; RT8562B High Voltage 8-CH LED Driver General Description The RT8562B is a 40V 8-CH LED driver capa.
Manufacture Richtek
Datasheet
Download RT8562B Datasheet




Richtek RT8562B
RT8562B
High Voltage 8-CH LED Driver
General Description
The RT8562B 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 RT8562B is
a current mode boost converter opearated at 1MHz, wide
VIN range covers from 4.5V 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 RT8562B automati-
cally detects and disconnects any unconnected and/or
broken strings during operation from PWM loop to prevent
VOUT from over voltage.
The 1.5% matched LED currents on all channels are simply
programmed with a resistor or a current sink. A very high
contrast ratio true digital PWM dimming can be achieved
by driving PWM pin with a PWM signal.
Other protecting features include programmable output
over voltage protection, LED curren limit, PWM switch
current limit and thermal shutdown.
The RT8562B is packaged with a tiny footprint package of
WQFN-24L 4x4 packages.
Ordering Information
RT8562B
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.
Marking Information
For marking information, contact our sales representative
directly or through a Richtek distributor located in your
area.
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 and High Accuracy Digital Dimming by PWM
Signal
z Programmable Soft-Start
z Automatic Detecting Unconnected and/or Broken
Channel
z Programmable Over Voltage Protection
z Disconnects LED in Shutdown
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)
24 23 22 21 20 19
EN 1
18 PGND2
NC 2
17 PGND1
SS 3
NC 4
GND
16 OVP
15 CH1
GND 5
PWM 6
14 CH2
25 13 CH3
7 8 9 10 11 12
WQFN-24L 4x4
DS8562B-06 June 2011
www.richtek.com
1



Richtek RT8562B
RT8562B
Typical Application Circuit
VOUT
L 40V MAX
VIN
10µH
D1
4.5V to 24V
R5
R4
10
C6
1µF
C1
10µF
RT8562B
23 VIN
LX1 19
LX2 20
C5
10µF
R7 C7
...: :
::
:
:
:
:
10 LED String
::
::
:
:
:
:
5V 1k
1 EN
CH1 15
R8
100k
CH2 14
PWM Signal
R1
1.8k
C2
3.9nF
C3
4.7µF
R6
1k 6 PWM
22 COMP
24 VDC
3 SS
C4
0.1µF
CH7 8
CH8 7
OVP 16
ISET 11
GND 5, 25 (Exposed Pad)
R2
RISET
4.75k
R3
ILED (mA) =
20 x 4.75
RISET (k)
VOUT
Note :
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 1. 1MHz, 20mA Full Scale Current PWM Dimming Control
Function Block Diagram
LX1, LX2
VIN
OVP
EN
VDC
COMP
SS
PWM
2.8V
1.2V
-
+
+
-
OSC
S
R
R
1.6V
-
+ Shutdown
5V
LDO
VOUT
Regulation
Unit
5uA
5V
+
-
+
-
+
-
+
+-
-
CH1
CH2
.
.
.
CH7
CH8
www.richtek.com
2
ISET
DS8562B-06 June 2011



Richtek RT8562B
RT8562B
Functional Pin Description
Pin No.
1
Pin Name
EN
Pin Function
Chip enable pin, when pulled low, chip is in shutdown mode. There
should be a pull low 100kΩ resistor connected to GND when the control
signal is floating.
2, 4, 21
NC
No Internal Connection.
3
5,
25 (Exposed Pad)
6
11
10, 9, 8, 7
15, 14, 13, 12
16
17, 18
SS
GND
PWM
ISET
CH5 to CH8
CH1 to CH4
OVP
PGND1, PGND2
Soft-Start pin, a capacitor of at least 10nF is required for soft start.
Ground pin of the chip. The exposed pad must be soldered to a large
PCB and connected to GND for maximum power dissipation.
Digital Dimming Control.
A resistor or a current from DAC on this pin programs the full LED current.
Channel 5 to Channel 8 LED Current Sink. Leave the pin unconnected if
not used.
Channel 1 to Channel 4 LED Current Sink. Leave the pin unconnected if
not used.
Over Voltage Protection. PWM boost converter turns off when VOVP goes
higher than 1.2V.
Power Ground (LX1/LX2 power return).
19, 20
LX1, LX2
PWM boost converter switch node.
22 COMP
PWM boost converter loop compensation node.
23 VIN
Power supply of the chip. For good bypass, a low ESR capacitor is
required.
24 VDC
Put 1μF capacitor on this pin to stabilize the 5V output of the internal
regulator. This regulator is for chip internal use only.
DS8562B-06 June 2011
www.richtek.com
3







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