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PDF RT8561D Data sheet ( Hoja de datos )
| Número de pieza | RT8561D | |
| Descripción | High Voltage 8-CH LED Driver | |
| Fabricantes | Richtek | |
| Logotipo |  |
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®
RT8561D
High Voltage 8-CH LED Driver
General Description
The RT8561Dis a 40V 8-CH LEDdriver capable of delivering
30mA to each channel with 10 LEDs (3.6V per diode), for
a total of 80 LEDs per driver. The RT8561D is a current-
mode Boost converter that operates at 1MHz, with a wide
VIN range from 4.5V to 24V and an on chip current switch
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 RT8561D
automatically detects and disconnects any unconnected
and/or broken strings during operation from the PWM loop
to prevent VOUT from over-voltage.
The 1.5% matched LED currents on all channels can be
simply adjustable with a resistor or a current sink. A very
high contrast true digital PWM dimming can be achieved
by driving the PWM pin with a PWM signal.
Other protections including adjustable programmable
output over-voltage protection, LED current limit, PWM
switch current limit and thermal shutdown are provided.
The RT8561D is available in the WQFN-24L 4x4 package.
Features
z High Voltage : VIN up to 24V, VOUT up to 40V
z Adjustable Channel Current from 10mA to 30mA
z 1.5% Channel Current Matching
z Current-Mode PWM 1MHz Boost Converter
z Easy and High Accuracy Digital Dimming by PWM
Signal
z Adjustable Soft-Start
z Automatic Detection of Unconnected and/or Broken
Channel
z Adjustable Over-Voltage Protection
z Disconnect Adjustable LED in Shutdown
z No Power Sequence Concern
z VIN Under-Voltage Lockout
z Over-Temperature Protection
z Current Limiting
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
Simplified Application Circuit
VIN
C1
R4
L1
RT8561D
VCC
C6
LX
R5
5V EN
LED1
PWM Signal
R6
ACTL
VC
LED2
LED7
LED8
C8 R1
CREG
OVP
C2
C3 SS RISET
C4 GND
VOUT
D1
C5
R7 C7
:
:
:
:
:
...
:
:
:
:
:
:
8 x 10 LED String
:
:: ::
R2
RISET
R3
VOUT
Copyright ©2013 Richtek Technology Corporation. All rights reserved.
DS8561D-00 May 2013
is a registered trademark of Richtek Technology Corporation.
www.richtek.com
1
1 page  
RT8561D
Parameter
Symbol
Test Conditions
Min Typ Max Unit
RISET Voltage
VRISET 3.6kΩ ≤ RISET ≤ 9.6kΩ, VACTL > 1.2V 1.17 1.2 1.23
V
Input Current of ACTL
IACTL
VACTL = 1.3V
-- 1 2 μA
VLED Threshold
Un-connection
-- 0.1 --
V
PWM Boost Converter
Switching Frequency
0.8 1 1.2 MHz
Minimum On-Time
-- 100 --
ns
Regulated VLED
Amplifier (gm) Output Current
VC Threshold
Highest Voltage LED String
2.4V > VC > 0.2V
PWM Switch Off
0.5 0.6 0.7
V
-- ±15 --
μA
0.1 0.2
--
V
LX RDS(ON)
LX Current Limit
ILIM
-- 0.3 0.5
2.5 --
--
Ω
A
OVP & Soft-Start
OVP Threshold
OVP Input Current
Soft-Start Current
Thermal Shutdown Threshold
Thermal Shutdown Hysteresis
VOVP
IOVP
ISS
TSD
VOVP ≤ 3V
VSS ≤ 2.5V
1.1 1.2 1.3
V
-- -- 50 nA
3 5 8 μA
-- 150 --
°C
-- 20 -- °C
Note 1. Stresses beyond those listed “Absolute Maximum Ratings” may cause permanent damage to the device. These are
stress ratings only, and functional operation of the device at these or any other conditions beyond those indicated in the
operational sections of the specifications is not implied. Exposure to absolute maximum rating conditions may affect
device reliability.
Note 2. θJA is measured at TA = 25°C on a high effective thermal conductivity four-layer test board per JEDEC 51-7. θJC is
measured at the exposed pad of the package.
Note 3. Devices are ESD sensitive. Handling precaution is recommended.
Note 4. The device is not guaranteed to function outside its operating conditions.
Copyright ©2013 Richtek Technology Corporation. All rights reserved.
DS8561D-00 May 2013
is a registered trademark of Richtek Technology Corporation.
www.richtek.com
5
5 Page 
Over-Voltage Protection
The RT8561D equips an Over-Voltage Protection (OVP)
function. When the voltage at the OVP pin reaches a
threshold of approximately 1.2V, the MOSFET driver
output (LX) will be turned “OFF”. The MOSFET driver
output (LX) will be turned “ON” again once the voltage at
OVP drops below the threshold voltage 1.2V.
Thus, the output voltage can be clamped at a certain
voltage level as shown in the following equation :
VOUT, OVP
=
VOVP
×
⎛⎜⎝1+
R2
R3
⎞⎟⎠
where
R2 and R3 are the resistors in a voltage divider connected
to the OVP pin.
VOVP is typically 1.2V.
If at least one string is in normal operation, the controller
will automatically ignore the open strings and continue to
regulate the current for the string(s) in normal operation.
Current Limit
The RT8561D can limit the peak current to achieve over-
current protection. The RT8561D senses the inductor
current through the LX pin during the switch-on period.
The duty cycle depends on the current sense signal
summed up with the internal slope compensation and
compared to the VC signal. The internal N-MOSFET will
be turned off when the current signal is larger than the
COMP signal. In the off period, the inductor current will
descend. The internal MOSFET is turned on by the
oscillator in the next beginning cycle.
Over-Temperature Protection
The RT8561D has an Over-Temperature Protection (OTP)
function to prevent overheating due to excessive power
dissipation. The OTP will shut down switching operation
when the junction temperature exceeds 150°C. The main
converter will start switching again once the junction
temperature cools down approximately by 20°C.
Power Sequence
The RT8561D can apply these power-on/off sequences
among VLED, EN and ACTL as shown in the charts below.
RT8561D
Hence, even when VIN is ready, the control circuit will
still wait for the arrival of PWM and EN before the LEDs
can react :
VIN
UVLO
VOUT
EN
ACTL
Figure 3. EN/ACTL Prior to VIN
VIN
UVLO
VOUT
EN
ACTL
Figure 4. VIN Tums Off Prior to EN/ACTL
VIN
VOUT
EN
ACTL
Figure 5. EN Prior to ACTL Signal
VIN
VOUT
EN
ACTL
Figure 6. EN Prior to ACTL Signal
Copyright ©2013 Richtek Technology Corporation. All rights reserved.
DS8561D-00 May 2013
is a registered trademark of Richtek Technology Corporation.
www.richtek.com
11
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| Páginas | Total 14 Páginas | |
| PDF Descargar | [ Datasheet RT8561D.PDF ] | |
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