RT8402
Phase-Cut Dimmable High Side Buck LED Driver with High
Power Factor
General Description
The RT8402 is a boundary mode controller that can
provide good PFC and be suitable for wall dimmer. The
RT8402 supports phase-cut dimmers, including
leading-edge (TRIAC) and trailing-edge dimmers. It is
used for buck converter and can be compatible with
TRIAC dimmer. The external MOSFET is switched by
internal gate driver and the feedback circuit regulates
output current precisely.
The RT8402 features a ZCS detector which keeps
system operating in BCM and obtaining excellent
power efficiency, better EMI performance.
The robust dimming control method can adjust the
output current following the TRIAC turn on angle and
avoid abnormal flicker.
This driver can use a cheap simple drum core inductor
in the system instead of an EE core to obtain high
efficiency.
The RT8402 is housed in a TSOT-23-6 package. Thus,
the components in the whole LED driver system can be
made very compact.
Features
Built-In Power MOSFET
Active Power Factor Correlation
Programmable
Constant LED Current with
High-Precision Current Regulation
Excellent Line And Load Regulation
Suit For High Side Buck Low BOM Cost
Requirement
Unique Dimming Control Method to be
compatible with TRIAC Dimmer
Used in Low Input Voltage Range
Support Low Percentage Dimming Angle
Built-in Over Thermal Protection
Output LED String Open Protection
Output LED String Short Protection
Over Current Protection
Applications
E27, PAR, Light Bar, Offline LED Lights
Pin Configuration
(TOP VIEW)
DIM
6
Ordering Information
RT8402
Package Type
J6 : TSOT-23-6
Lead Plating System
G : Green (Halogen Free and Pb Free)
VC SENSE
5
4
2
3
VCC SGND GATE
Note :
Richtek products are :
TSOT-23-6
Marking Information
2Q=DNN
2Q= : Product Code
DNN : Date Code
RoHS compliant and compatible with the current
requirements of IPC/JEDEC J-STD-020.
Suitable for use in SnPb or Pb-free soldering processes
Copyright © 2017 Richtek Technology Corporation. All rights reserved.
is a registered trademark of Richtek Technology Corporation.
DS8402-00
January 2017
www.richtek.com
1
RT8402
Simplified Application Circuit
Bridge Rectifier
Line
Neutrl
C
IN
R1
R2A
ZD1
R3
RT8402
DIM
VCC
VC
SENSE
RG
Q1
D2
Bootstrap diode
C1
C2
R2B
C3
SGND
GATE
R4
L1
+
EC1
D1
Functional Pin Description
Pin No.
1
2
3
4
5
6
Pin Name
VCC
SGND
GATE
SENSE
VC
DIM
Pin Function
Supply voltage input of the chip. For good bypass, a ceramic capacitor near the
VCC pin is required.
Ground of the chip.
Gate driver for external MOSFET.
LED current sense input.
Close loop compensation node.
Internal dimming function.
Copyright © 2017 Richtek Technology Corporation. All rights reserved.
is a registered trademark of Richtek Technology Corporation.
www.richtek.com
2
DS8402-00
January 2017
RT8402
Functional Block Diagram
VCC
Regulator
SENSE
+
EA
-
State
Machine
A
GATE
+
-
250mV
Duty
Detection
SGND
VC
DIM
Operation
The RT8402 senses the average output current and
regulates the current precisely. The VC pin is the
stability compensation node in this close loop. To
stabilize the system and achieve better PFC / THDi,
proper selection of a compensation network is needed.
By using boundary mode control, it provides good
efficiency performance. The dimming characteristic can
be optimized by adjusting the external setting of DIM
pin.
Copyright © 2017 Richtek Technology Corporation. All rights reserved.
is a registered trademark of Richtek Technology Corporation.
DS8402-00
January 2017
www.richtek.com
3
RT8402
Absolute Maximum Ratings
(Note 1)
VCC Supply Voltage, VCC -------------------------------------------------------------------------------------- 40V
VC, DIM, SENSE to SGND Voltage ---------------------------------------------------------------------------
0.3V
to 6V
Power Dissipation, P
D
@ T
A
= 25C
TSOT-23-6 ------------------------------------------------------------------------------------------------------------
0.44W
Package Thermal Resistance
(Note 2)
TSOT-23-6,
JA
------------------------------------------------------------------------------------------------------
226.5C/W
TSOT-23-6,
JC
------------------------------------------------------------------------------------------------------
18.9C/W
Lead Temperature (Soldering, 10 sec.) ------------------------------------------------------------------------
260C
Junction Temperature ----------------------------------------------------------------------------------------------
150C
Storage Temperature Range -------------------------------------------------------------------------------------
65C
to 150C
ESD Susceptibility
(Note 3)
HBM (Human Body Model) ---------------------------------------------------------------------------------------
2kV
Recommended Operating Conditions
(Note 4)
VCC Supply Voltage -------------------------------------------------------------------------------------------------
10V
to 30V
Ambient Temperature Range--------------------------------------------------------------------------------------
40C
to 85C
Junction Temperature Range -------------------------------------------------------------------------------------
40C
to 125C
Electrical Characteristics
(V
CC
= 24V, T
A
= 25C, unless otherwise specified)
Parameter
VCC UVLO ON
VCC UVLO OFF
VCC Shutdown Current
VCC Operating Current
VCC 30V Operating Current
VCC OVP Level
VCC Clamp Level
VCC Clamp Current
Sense Pin Leakage Current
Current Sense Threshold
DIM Pin Leakage Current
GATE Voltage High
Symbol
V
UVLO_ON
V
UVLO_OFF
I
SD
I
CC
I
CC
V
OVP
V
CC_CLAMP
I
CC_CLAMP
I
SENSE
V
SENSE
I
DIM
V
GATE_H
Test Conditions
Min
17
6
Typ
18
6.8
--
1.8
2.7
37
29
0.85
--
250
--
12.5
12
Max
19
7.6
2
2.5
3.4
39.5
--
--
2
260
1
15
15
Unit
V
V
A
mA
mA
V
V
mA
A
mV
A
V
V
CC
= V
UVLO_ON
3V
By CGATE = 1nF, V
CC
=24V
V
C
=1V, SENSE = 0V
By CGATE = 1nF, V
CC
= 30V
V
C
=1V, SENSE = 0V
--
1.1
2
34.5
--
--
V
SENSE
= 3V
--
240
V
DIM
= 5V
I
GATE
= 0mA
I
GATE
= 10mA
--
10
9
Copyright © 2017 Richtek Technology Corporation. All rights reserved.
is a registered trademark of Richtek Technology Corporation.
www.richtek.com
4
DS8402-00
January 2017
RT8402
Parameter
GATE Driver
Rising Time
Falling Time
t
R
t
F
Symbol
Test Conditions
C
L
= 1nF
C
L
= 1nF
Min
--
--
Typ
80
50
Max
--
--
Unit
ns
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.
JA
is measured under natural convection (still air) at T
A
= 25C with the component mounted on a low
effective-thermal-conductivity two-layer test board on a JEDEC thermal measurement standard.
JC
is measured at the
exposed pad of the package.
Note 3.
Devices are ESD sensitive. Handling precaution recommended.
Note 4.
The device is not guaranteed to function outside its operating conditions
Copyright © 2017 Richtek Technology Corporation. All rights reserved.
is a registered trademark of Richtek Technology Corporation.
DS8402-00
January 2017
www.richtek.com
5
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