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PDF RT8567 Data sheet ( Hoja de datos )
| Número de pieza | RT8567 | |
| Descripción | 6-CH 43V WLED Driver | |
| Fabricantes | Richtek | |
| Logotipo |  |
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RT8567
6-CH 43V WLED Driver
General Description
The RT8567 is a high efficiency driver for white LEDs. It is
designed for LCD panels that employ an array of LEDs as
the lighting source. An integrated current mode boost
controller drives six strings in parallel and supports up to
12 WLEDs per string. The internal current sinks support
a maximum of ±2% current mismatching for excellent
brightness uniformity in each string of LEDs. To provide
enough headroom for current sink operation, the boost
controller monitors the minimum voltage of the feedback
pins and regulates an optimized output voltage for power
efficiency.
The RT8567 has a wide input voltage range from 2.7V to
24V and can provide adjustable LED current from 5mA to
40mA. The internal 250mΩ, 43V power switch with current
mode control provides cycle-by-cycle over current
protection. The RT8567 also integrates PWM dimming
function for accurate LED current control. The input PWM
dimming frequency can operate from 200Hz to 25kHz
without inducing any inrush in LED current or inductor
current. The switching frequency of the RT8567 is also
adjustable from 500kHz to 2MHz, which allows flexibility
between efficiency and component size.
The RT8567 is available in a thin WQFN-20L 3x3 package.
Ordering Information
RT8567
Package Type
QW : WQFN-20L 3x3 (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 Wide Input Voltage : 2.7V to 24V
z High Output Voltage : Up to 43V
z Channel Current Programmable : 5mA to 40mA
z Channel Current Regulation with Accuracy ±3% and
Matching ±2%
z Dimming Controls : External PWM Input Up to 25kHz
z Adjustable Switching Frequency : 500kHz to 2MHz
z Built-In Soft-Start
z Protections
` LED Strings Open Detection
` Current Limit Protection
` Programmable Over Voltage Protection
` Over Temperature Protection
z 20-Lead WQFN Package
z RoHS Compliant and Halogen Free
Applications
z UMPC and Notebook Computer Backlight
z GPS, Portable DVD Backlight
Pin Configurations
(TOP VIEW)
VDC
EN
RT
ISET
NC
20 19 18 17 16
1 15 PGND
2 14 OVP
3 AGND 13 NC
4 21 12 CH1
5 11 CH2
6 7 8 9 10
WQFN-20L 3x3
Marking Information
JY= : Product Code
JY=YM
DNN
YMDNN : Date Code
DS8567-00 April 2011
www.richtek.com
1
1 page  
RT8567
Absolute Maximum Ratings (Note 1)
z VIN to GND ------------------------------------------------------------------------------------------------------------------ −0.3V to 26.5V
z EN, PWM, VDC, ISET, COMP, RT to GND -------------------------------------------------------------------------- −0.3V to 26.5V
z LX to GND ------------------------------------------------------------------------------------------------------------------- −0.3V to 48V
z OVP, (CH1 to CH6) to GND --------------------------------------------------------------------------------------------- −0.3V to 48V
z Power Dissipation, PD @ TA = 25°C
WQFN−20L 3x3 ------------------------------------------------------------------------------------------------------------ 1.471W
z Package Thermal Resistance (Note 2)
WQFN−20L 3x3, θJA ------------------------------------------------------------------------------------------------------ 68°C/W
WQFN−20L 3x3, θJC ------------------------------------------------------------------------------------------------------ 7.5°C/W
z Lead Temperature (Soldering, 10 sec.) ------------------------------------------------------------------------------- 260°C
z Junction Temperature ----------------------------------------------------------------------------------------------------- 150°C
z Storage Temperature Range -------------------------------------------------------------------------------------------- −65°C to 150°C
z ESD Susceptibility (Note 3)
HBM -------------------------------------------------------------------------------------------------------------------------- 2kV
MM ---------------------------------------------------------------------------------------------------------------------------- 200V
Recommended Operating Conditions (Note 4)
z Supply Input Voltage, VIN ------------------------------------------------------------------------------------------------ 2.7V to 24V
z Junction Temperature Range -------------------------------------------------------------------------------------------- −40°C to 125°C
z Ambient Temperature Range -------------------------------------------------------------------------------------------- −40°C to 85°C
Electrical Characteristics
(VIN = 4.5V, TA = 25°C, unless otherwise specified)
Parameter
Symbol
Test Conditions
Min Typ Max Unit
VIN Quiescent Current
IVCC
IVCC_LX
VCOMP = 0V, No Switching
VCOMP = 2V, Switching
-- 2 --
mA
-- 3 --
Shutdown Current
VIN Under Voltage Lockout
Threshold
Control Input
ISHDN
VUVLO
VIN = 4.5V, EN = 0
VIN Rising
VIN Falling
-- -- 20 μA
-- 2.3 --
-- 2.1 --
V
EN Input Voltage
Threshold
PWM Input Voltage
Threshold
Boost Converter
Logic-High VIH
Logic-Low VIL
Logic-High VIH
Logic-Low VIL
VIN = 2.7V to 24V
VIN = 2.7V to 24V
VIN = 2.7V to 24V
VIN = 2.7V to 24V
2 -- --
V
-- -- 0.8
1.5 --
--
V
-- -- 0.6
Switching Frequency
LX On Resistance (N-MOSFET)
Minimum On Time
fOSC
RDS(ON)
tMON
RRT = 25kΩ
RRT = 51kΩ
RRT = 100kΩ
VIN > 4.5V
fOSC = 1MHz
-- 2 --
0.9 1 1.1 MHz
-- 0.5 --
-- 0.25 --
Ω
-- 120 --
ns
Maximum Duty
LX Current Limit
Regulated VCHx
DMAX
ILIM
VCHx
VCOMP = 2V, Switching
Highest LED String, ILED = 20mA
--
1.6
--
94 --
%
2 2.4 A
0.6 --
V
To be continued
DS8567-00 April 2011
www.richtek.com
5
5 Page 
RT8567
where TJ(MAX) is the maximum junction temperature, TA is
the ambient temperature, and θJA is the junction to ambient
thermal resistance.
For recommended operating condition specifications of
the RT8567, the maximum junction temperature is 125°C
and TA is the ambient temperature. The junction to ambient
thermal resistance, θJA, is layout dependent. For
WQFN-20L 3x3 packages, the thermal resistance, θJA, is
68°C/W on a standard JEDEC 51-7 four-layer thermal test
board. The maximum power dissipation at TA = 25°C can
be calculated by the following formula :
PD(MAX) = (125°C − 25°C) / (68°C/W) = 1.471W for
WQFN-20L 3x3 package
The maximum power dissipation depends on the operating
ambient temperature for fixed TJ(MAX) and thermal
resistance, θJA. For the RT8567 package, the derating
curve in Figure 2 allows the designer to see the effect of
rising ambient temperature on the maximum power
dissipation.
1.6
Four-Layer PCB
1.4
1.2
1.0
0.8
0.6
0.4
0.2
0.0
0
25 50 75 100 125
Ambient Temperature (°C)
Figure 2. Derating Curve for RT8567 Package
Layout Considerations
PCB layout is very important for designing switching power
converter circuits. The following layout guides should be
strictly followed for best performance of the RT8567.
` The power components L1, D1, CIN, COUT must be placed
as close to the IC as possible to reduce current loop.
The PCB trace between power components must be as
short and wide as possible.
` Place L1 and D1 as close to the LX pin as possible. The
trace should be as short and wide as possible.
` The compensation circuit should be kept away from
the power loops and shielded with a ground trace to
prevent any noise coupling. Place the compensation
components as close to the COMP pin as possible.
` The exposed pad of the chip should be connected to
ground plane for thermal consideration.
The compensation circuit should be kept away from The power loops
and shielded with a ground trace to prevent any noise coupling.
GND
VIN
CIN GND
C3
C2 C4 L1
Place the power
components as
Close as possible.
The traces should
be wide and short
especially for the
high current loop.
Locate the C2 as
close to VIN as
possible.
R3 D1
VOUT
Locate RISET as
close to ISET
as possible.
RISET
GND
VDC
EN
RT
ISET
NC
20 19 18 17 16
1 15 PGND
2 14 OVP
3 AGND 13 NC
4 21 12 CH1
5 11 CH2
6 7 8 9 10
COUT
Figure 3. PCB Layout Guide
DS8567-00 April 2011
www.richtek.com
11
11 Page | ||
| Páginas | Total 12 Páginas | |
| PDF Descargar | [ Datasheet RT8567.PDF ] | |
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