Richtek RT8511BGQW Schematic [ru]
®
43V Asynchronous Boost WLED Driver
RT8511B
General Description
The RT851 1B is an LED driver IC that can support up to
10 WLED in series. It is composed of a current mode
boost converter integrated with a 43V/2.2A power switch
running at a fixed 500kHz frequency and covering a wide
VIN ra nge from 2.7V to 24V.
The white LED current is set with a n external resistor , and
the feedback voltage is regulated to 200mV (typ.). During
operation, the LED current ca n be controlled by the PWM
input signal in which the duty cycle determines the
feedback reference voltage.
For brightness dimming, the RT851 1B is able to maintain
steady control of the LED current. Therefore, no audible
noises are generated on the output cap acitor . The RT851 1B
also has programmable over voltage pin to prevent the
output from exceeding absolute maximum ratings during
open LED conditions. The RT8511B is available in
W DF N-8L 2x2 package.
Features
Wide Input Voltage Range : 2.7V to 24V
High Output Voltage : up to 43V
Direct PWM Dimming Control and Frequency from
100Hz to 8kHz
Internal Soft-Start and Compensation
200mV Reference Voltage
PWM Dimming with Internal Filter
Programmable Over Voltage Protection
Over Temperature Protection
Current Limit Protection
Thin 8-Lead WDFN Package
RoHS Compliant and Halogen Free
Applications
UMPC and Notebook Computer Backlight
GPS, Portable DVD Backlight
Ordering Information
RT8511B
Package Type
QW : WDFN-8L 2x2 (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.
Pin Configurations
(TOP VIEW)
1
OVP
2
FB
3
DIMC
GND
WDFN-8L 2x2
GND
4
9
Marking Information
0F : Product Code
0FW
W : Date Code
8
7
6
5
EN
PWM
VIN
LX
Copyright 2015 Richtek Technology Corporation. All rights reserved. is a registered trademark of Richtek Technology Corporation.
©
DS8511B-05 February 2015 www.richtek.com
1
RT8511B
Typical Application Circuit
V
4.2V to 24V
Chip Enable
100Hz to 8kHz
V
2.7V to 24V
Chip Enable
100Hz to 8kHz
IN
PWM
LED
2.7V to 4.2V
PWM
C
IN
1µF x 2
C
DIMC
1µF
Figure 1. T ypical Application Circuit of Normal Operation
C
LED
1µF x 2
V
IN
C
DIMC
1µF
C
1µF
IN
6
8
7
3
6
8
7
3
VIN
EN
PWM
DIMC
VIN
EN
PWM
DIMC
L
10µH
RT8511B
L
10µH
RT8511B
5
LX
1
OVP
2
FB
4, 9 (Exposed Pad)
GND
5
LX
1
OVP
2
FB
4, 9 (Exposed Pad)
GND
V
D
R2
3.3M
C
OUT
1µF x 2
R1
100k
D
R2
3.3M
C
OUT
1µF x 2
R1
100k
:
:
:
:
OUT
:
:
:
:
WLEDs
:
:
:
:
R
SET
3.3
V
OUT
:
:
:
:
:
:
:
:
WLEDs
:
:
:
:
R
SET
3.3
Figure 2. T ypical Application Circuit of Low V oltage Operation
Functional Pin Description
Pin No. Pin Name Pin Function
1 OVP Over Voltage Protection for Boost Converter. The detecting threshold is 1.2V.
2 FB Feedback. Connect a resistor between this pin and GND to set the LED current.
3 DIMC PW M Fil t er. Filter the PW M sig nal to a DC vol t ag e.
4 GND Ground.
5 LX Switch Node for Boost Converter.
6 VIN Power Supply Input.
7 PWM Dimming Control Input.
8 EN Chip Enable (Active High) for Boost Converter.
9 (Exp ose d Pa d) GN D
Copyright 2015 Richtek Technology Corporation. All rights reserved. is a registered trademark of Richtek Technology Corporation.
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The exposed pad must be soldered to a large PCB and connected to AGND for
ma x imum power dissipation.
DS8511B-05 February 2015www.richtek.com
Function Block Diagram
RT8511B
LXOVP
VIN
EN
PWM
DIMC
FB
OSC
PWM
Controller
D/A
Dimming
+
1.2V
-
QS
R
Q
+
+
-
OTP
OCP
GND
Copyright 2015 Richtek Technology Corporation. All rights reserved. is a registered trademark of Richtek Technology Corporation.
©
DS8511B-05 February 2015 www.richtek.com
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RT8511B
Absolute Maximum Ratings (Note 1)
VIN, EN, PWM, DIMC to GND------------------------------------------------------------------------------------------ −0.3V to 26.5V
FB, OVP to GND ---------------------------------------------------------------------------------------------------------- −0.3V to 48V
LX to GND ------------------------------------------------------------------------------------------------------------------ −0.3V to 48V
< 500ns ---------------------------------------------------------------------------------------------------------------------- −1V to 48V
Power Dissipation, P
WDFN-8L 2x2 -------------------------------------------------------------------------------------------------------------- 0.833W
Package Thermal Re sistance (Note 2)
W DF N-8L 2x2, θJA--------------------------------------------------------------------------------------------------------- 120°C/W
WDFN-8L 2x2, θJC--------------------------------------------------------------------------------------------------------- 8.2°C/W
Lead Temperature (Soldering, 10 sec.)------------------------------------------------------------------------------- 260°C
Junction T emperature----------------------------------------------------------------------------------------------------- 150°C
Storage T emperature Range -------------------------------------------------------------------------------------------- –65°C to 150°C
ESD Susceptibility (Note 3)
HBM (Human Body Model)---------------------------------------------------------------------------------------------- 2kV
MM (Machine Model) ----------------------------------------------------------------------------------------------------- 200V
@ TA = 25°C
D
Recommended Operating Conditions
Supply Input V oltage, V
Junction T emperature Range-------------------------------------------------------------------------------------------- −40°C to 125°C
Ambient T emperature Range-------------------------------------------------------------------------------------------- −40°C to 85°C
------------------------------------------------------------------------------------------------ 2.7V to 24V
IN
(Note 4)
Electrical Characteristics
(V
= 4.5V, T
IN
VIN Quiescent Current
VIN Shutdown Current I
Control In put
EN, PWM
Threshold Voltage
EN Sink Current IIH V
Shutdown Delay t
PWM Dimming Frequenc y 0.1 - - 8 kHz
Boost Converter
= 25°C, unless otherwise specified)
A
Parameter Symbol Test Conditions Min Typ Max Unit
Logic-High V
V
I
Q
I
VFB = 0V, Switching -- -- 2.2 mA
Q_SW
V
SHDN
V
IH
= 1.5V, No Switching -- 725 -- A
FB
= 4.5V, VEN = 0V -- 1 4 A
IN
= 2.7V to 24V 1.6 -- --
IN
V
Logic-Low VIL V
EN high to low 52 64 80 ms
SHDN
= 2.7V to 24V -- -- 0.8
IN
= 3V 1 -- 10 A
EN
Switching Frequency f
LX On Resistance
(N-MOSFET)
V
OSC
R
VIN > 5V -- 0.4 0.6
DS(ON)
= 2.7V to 24V 0.4 0.5 0.6 MHz
IN
Minimum ON T i me -- 6 0 -- ns
Maximum Duty Cycle D
Copyright 2015 Richtek Technology Corporation. All rights reserved. is a registered trademark of Richtek Technology Corporation.
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V
MAX
= 0V, Switching -- 92 -- %
FB
DS8511B-05 February 2015www.richtek.com
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