®
RT7320
High Voltage Programmable Constant-Current LED Driver
General Description
The RT7320 is a simple and robust constant-current
regulator designed to provide a cost-effective solution for
driving high-voltage LEDs in LED lamp applications. The
wide input voltage range (up to 400V) allows flexible LED
string design to operate with 110V
RMS
or 220V
RMS
AC input
voltage.
The RT7320 allows users to set the regulated current level
by connecting the pins from I1 to I5 for various LED lamps.
Parallel LED strings operation is possible with right
regulated current setting on the RT7320. In addition, the
RT7320 also provides a thermal regulation protection,
instead of traditional thermal shutdown, to suppress the
rise of IC junction temperature and prevent LED lamps
from flicker.
Features
Programmable Regulated Current : 2.8mA to
78.3mA
AC Input Voltage : 90 to 130V
RMS
or 200 to 240V
RMS
Thermal Regulation Protection
Minimized Start-up Time (<10ms)
Easy EMI Solution
Minimized BOM Cost and Space Required
Small SOP-8 (Exposed Pad) Package
RoHS Compliant and Halogen Free
Applications
High-Voltage LED Lamps
High-Voltage Sinking Current Regulator
Marking Information
RT7320GSP : Product Number
Ordering Information
RT7320
Package Type
SP : SOP-8 (Exposed Pad-Option 2)
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.
RT7320
GSPYMDNN
YMDNN : Date Code
Pin Configurations
(TOP VIEW)
OUT
NC
GND
I1
2
3
4
8
7
I5
I4
I3
I2
GND
9
6
5
SOP-8 (Exposed Pad)
Simplified Application Circuit
+
…
AC
C1
RT7320
OUT
I5
I4
GND
I1
I3
I2
Copyright
©
2013 Richtek Technology Corporation. All rights reserved.
is a registered trademark of Richtek Technology Corporation.
DS7320-00
September 2013
www.richtek.com
1
RT7320
Functional Pin Description
Pin No.
1
2
3,
9 (Exposed Pad)
4
5
6
7
8
Pin Name
OUT
NC
GND
I1
I2
I3
I4
I5
Pin Function
Output of the Constant-Current Regulator. A programmable regulated current,
flowing into this pin, drives high-voltage LEDs connected between this pin and
the rectified voltage.
No Internal Connection.
Ground. The exposed pad must be soldered to a large PCB and connected to
GND for maximum power dissipation.
Current Setting Input. If this pin is directly connected to GND, the regulated
current increases 2.8mA (typical).
Current Setting Input. If this pin is directly connected to GND, the regulated
current increases 5.5mA (typical).
Current Setting Input. If this pin is directly connected to GND, the regulated
current increases 10mA (typical).
Current Setting Input. If this pin is directly connected to GND, the regulated
current increases 20mA (typical).
Current Setting Input. If this pin is directly connected to GND, the regulated
current increases 40mA (typical).
Function Block Diagram
Voltage
Regulator
OUT
Thermal
Regulation
Protection
+
V
REF
M1
Error
Amplifier
-
GND
R1 = 16R
I
1
2.8mA
R2 = 8R
I
2
5.5mA
R3 = 4R
I
3
10mA
R4 = 2R
I
4
20mA
R5 = R
I
5
40mA
I1
I2
I3
I4
I5
Copyright
©
2013 Richtek Technology Corporation. All rights reserved.
is a registered trademark of Richtek Technology Corporation.
www.richtek.com
2
DS7320-00
September 2013
RT7320
Operation
Constant-Current Regulator
The constant-current regulator in the RT7320 consists of
an output high-voltage MOSFET (M1), programmable
current-sense resistors (R1 to R5), an error amplifier and
a reference voltage (V
REF
). The error amplifier, designed
with high DC gain, compares the current signal (V
CS
) on
the current-sense resistors and the V
REF
to generate an
amplified error signal. The error signal regulates the output
MOSFET to control the sinking current on the OUT pin at
the programmed current level. In addition, the operating
OUT voltage (V
OUT
) must be higher than the minimum
OUT voltage (V
OUT_MIN
). Otherwise, the output current
might not be regulated at the programmed level (I
OUT_SET
).
The V
OUT_MIN
is approximately calculated by the following
equation :
V
OUT_MIN
= 3000 x I
OUT_SET2
+ 4 (V)
Thermal Regulation Protection
When a LED lamp operates in high ambient temperature
conditions, it needs a thermal protection to limit the
temperatures for protecting LED lamps and ensuring
system reliability. The RT7320 provides a thermal
regulation protection, instead of traditional thermal
shutdown, to suppress the rise of temperatures. When
the IC junction temperature rises above 125°C (typ.), this
function starts to gradually reduce the regulated LED
current, depending on the rise of the junction temperature.
Meanwhile, the system power dissipation is also reduced.
Finally, the temperatures in the system will be well
controlled and enter their steady-state. The function can
achieve both of the two targets : to protect LED lamps and
to prevent them from flicker.
Copyright
©
2013 Richtek Technology Corporation. All rights reserved.
is a registered trademark of Richtek Technology Corporation.
DS7320-00
September 2013
www.richtek.com
3
RT7320
Absolute Maximum Ratings
(Note 1)
−0.3V
to 250V
−0.3V
to 5V
3.44W
29°C/W
2°C/W
OUT to GND ---------------------------------------------------------------------------------------------------------------
I1, I2, I3, I4, I5 to GND ---------------------------------------------------------------------------------------------------
Power Dissipation, P
D
@ T
A
= 25°C
SOP-8 (Exposed Pad) --------------------------------------------------------------------------------------------------
Package Thermal Resistance (Note 2)
SOP-8 (Exposed Pad),
θ
JA
---------------------------------------------------------------------------------------------
SOP-8 (Exposed Pad),
θ
JC
--------------------------------------------------------------------------------------------
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 Model) --------------------------------------------------------------------------------------------- 2kV
MM (Machine Model) ---------------------------------------------------------------------------------------------------- 200V
Recommended Operating Conditions
(Note 4)
0V to 100V
2.8mA to 78.3mA
−40°C
to 85°C
−40°C
to 125°C
Input DC Voltage, V
OUT
--------------------------------------------------------------------------------------------------
Input Current, I
OUT
--------------------------------------------------------------------------------------------------------
Ambient Temperature Range -------------------------------------------------------------------------------------------
Junction Temperature Range -------------------------------------------------------------------------------------------
Electrical Characteristics
(T
A
= 25°C, unless otherwise specification)
Parameter
OUT Section
OUT Regulated Current Level-1
OUT Regulated Current Level-2
OUT Regulated Current Level-3
OUT Regulated Current Level-4
Symbol
Test Conditions
Min
Typ
Max
Unit
I
1
I
2
I
3
I
4
I
5
V
OU
T
= 30V, I1 = GND
V
OU
T
= 30V, I2 = GND
V
OU
T
= 30V, I3 = GND
V
OUT
= 30V, I4 = GND
V
OUT
= 30V, I3 = I4 = GND
V
OUT
= 30V, I5 = GND
2.66
5.225
9.5
19
28.5
38
2.8
5.5
10
20
30
40
2.94
5.775
10.5
21
31.5
42
mA
mA
mA
mA
mA
mA
OUT Regulated Current Level-34 I
34
OUT Regulated Current Level-5
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.
θ
JA
is measured at T
A
= 25°C on a high effective thermal conductivity four-layer test board per JEDEC 51-7.
θ
JC
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.
is a registered trademark of Richtek Technology Corporation.
www.richtek.com
4
DS7320-00
September 2013
RT7320
Typical Application Circuit
+
…
AC
C1
RT7320
1 OUT
3, 9 (Exposed Pad)
I5 8
I4 7
I3 6
I2 5
GND
4 I1
Copyright
©
2013 Richtek Technology Corporation. All rights reserved.
is a registered trademark of Richtek Technology Corporation.
DS7320-00
September 2013
www.richtek.com
5
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