RT8453B
1.5A, 500kHz, 40V High Voltage Buck LED Driver
General Description
The RT8453B is a buck current mode PWM regulator for
LED driving applications. It provides an integrated 1.5A
switch and can be operated with a wide input voltage range
from 4.5V to 40V. With a 500kHz operating frequency, the
RT8453B allows all external inductor and input/output
capacitors to be small. High efficiency is achieved with its
190mV current sensing capability. Dimming can be either
analog or PWM digital signal driven. The RT8453B is
available in a small SOP-8 (Exposed pad) package.
Features
Input Operating Range 4.5 to 40V
1.5A Switching Current Limitation
10% Constant Current Output Accuracy
Current Mode PWM with 500kHz Switching
Frequency
Analog or PWM Control Signal for LED Dimming
Programmable Soft Start
Input Under Voltage Lockout
Over Temperature Protection
RoHS Compliant and Halogen Free
Ordering Information
RT8453B
Package Type
SP : SOP-8 (Exposed Pad-Option 2)
Operating Temperature Range
G : Green (Halogen Free with Comme-
rcial Standard)
Note :
Richtek Green 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.
Applications
General Illumination
Desk Lights and Room Lighting
Industrial Backlight/Lighting
Constant Current Source
Pin Configurations
(TOP VIEW)
ISN
VC
ACTL
EN
2
3
4
8
VCC
SW
GND
SS
GND
9
7
6
5
Marking Information
RT8453BGSP : Product Number
RT8453B
GSPYMDNN
YMDNN : Date Code
SOP-8 (Exposed Pad)
DS8453B-00 August 2010
www.richtek.com
RT8453B
Typical Application Circuit
V
IN
4.5V to 40V
10
C2
RT8453B
Analog
Dimming
or
PWM
Dimming Control
5V
R5
10k
C6
3.3nF
C3
10nF
4 EN
2
VC
5
SS
SW
7
L1
22µH
8 VCC
3 ACTL
ISN 1
R2
190mV
R3
R4
D1
C1
GND
6, 9 (Exposed Pad)
Functional Pin Description
Pin No.
1
2
3
4
5
Pin Name
ISN
VC
ACTL
EN
SS
Pin Function
Current Sense Amplifier Negative Input. Voltage threshold between V
CC
and ISN
is 190mV.
PWM Converter Loop Compensation Node.
Analog Dimming Control. Effective programming range is between 0.3V and 1.2V.
Chip Enable (Active High). When low, chip is in shutdown mode.
Soft Start. A capacitor of at least 10nF is required for soft start.
Ground. The exposed pad must be soldered to a large PCB and connected to
GND for maximum power dissipation.
PWM Converter Switch Node.
Power Supply of the Chip. For good bypass, a low ESR capacitor is required.
6,
GND
9 (Exposed Pad)
7
8
SW
VCC
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DS8453B-00 August 2010
RT8453B
Function Block Diagram
SW
OSC
VCC
4.5V
EN
1.4V
VC
6µA
SS
-
GM
+
-
+
S
R
R
+
-
Shutdown
-
+
ISN
V
CC
ACTL
+
-
GND
V
CC
– V
ISN
(mV)
190
0
0.3
1.2
V
ACTL
(V)
Figure 1
DS8453B-00 August 2010
www.richtek.com
RT8453B
Absolute Maximum Ratings
(Note 1)
45V
45V
8V (Note 6)
20V
1.333W
Supply Input Voltage, V
CC
-----------------------------------------------------------------------------------------------
SW Pin Voltage at Switching Off, ISN --------------------------------------------------------------------------------
ACTL -------------------------------------------------------------------------------------------------------------------------
EN -----------------------------------------------------------------------------------------------------------------------------
Power Dissipation, P
D
@ T
A
= 25°C
SOP-8 (Exposed Pad) ---------------------------------------------------------------------------------------------------
Package Thermal Resistance (Note 2)
SOP-8 (Exposed Pad),
θ
JA
--------------------------------------------------------------------------------------------- 75°C/W
SOP-8 (Exposed Pad),
θ
JC
--------------------------------------------------------------------------------------------- 15°C/W
Junction Temperature ----------------------------------------------------------------------------------------------------- 150°C
Lead Temperature (Soldering, 10 sec.) ------------------------------------------------------------------------------- 260°C
Storage Temperature Range --------------------------------------------------------------------------------------------
−65°C
to 150°C
ESD Susceptibility (Note 3)
HBM (Human Body Mode) ---------------------------------------------------------------------------------------------- 2kV
MM (Machine Mode) ------------------------------------------------------------------------------------------------------ 200V
Recommended Operating Conditions
(Note 4)
Supply Input Voltage ------------------------------------------------------------------------------------------------------ 4.5V to 40V
Junction Temperature Range --------------------------------------------------------------------------------------------
−40°C
to 125°C
Electrical Characteristics
(V
CC
= 12V, No Load, T
A
= 25°C, unless otherwise specified)
Parameter
Overall
Supply Current
Shutdown Current
EN Input Threshold Logic-High
Voltage
Logic-Low
Current Sense Amplifier
Sense Threshold Voltage (V
CC
−
V
ISN
)
ISN Pin Input Current
VC Pin Output Current
VC Threshold for PWM Switch Off
LED Dimming
Analog Dimming ACTL Pin Input
Current
LED Current Off Threshold at
ACTL
PWM BOOST Converter
Switching Frequency
Symbol
I
VCC
I
SHDN
V
EN_H
V
EN_L
Test Conditions
VC
≤
0.4V (Switching off)
V
EN
≤
0.7V
Min
--
--
1.5
--
Typ
4
250
--
--
Max
6
--
--
Unit
mA
μA
V
0.5
4.5V
≤
common mode
≤
40V
I
ISN
I
VC
V
ISN
= 24V
2.4V > VC > 0.2V
170
--
--
--
190
40
±20
0.7
210
--
--
--
mV
μA
μA
V
I
ACTL
V
ACTL
0.3V
≤
V
ACTL
≤
1.2V
--
--
--
0.2
3
--
μA
V
f
SW
400
500
600
kHz
To be continued
www.richtek.com
DS8453B-00 August 2010
RT8453B
Parameter
Maximum Duty Cycle
SW On-Voltage
SW Current Limit
Soft-Start
Soft-Start Current
Over Temperature Protection
Thermal Shutdown Temperature T
SD
Thermal Shutdown Hysteresis
ΔT
SD
--
--
150
10
--
--
°C
°C
I
SS
V
SS
≤
2V
--
6
--
μA
(Note 5)
V
SW
I
LIM_SW
I
SW
= 0.5A
Symbol
Test Conditions
Min
--
--
1.25
Typ
88
0.4
1.5
Max
--
--
--
Unit
%
V
A
Note 1.
Stresses listed as the above "Absolute Maximum Ratings" may cause permanent damage to the device. These are
for stress ratings. 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 for
extended periods may remain possibility to affect device reliability.
Note 2.
θ
JA
is measured in natural convection at T
A
= 25°C on a high effective thermal conductivity four-layer test board of
JEDEC 51-7 thermal measurement standard. The measurement case position of
θ
JC
is on 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.
Note 5.
When the natural maximum duty cycle of 500kHz switching frequency is reached, the switching cycle will be skipped
(not reset) as the operating condition requires to effectively stretch and achieve higher on cycle.
Note 6.
If connected with a 20kΩ series resistor, this pin can go up to 40V.
DS8453B-00 August 2010
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