20160322025944 8293

WS3412 ProductDescription
Non-isolated Buck APFC Offline LED Driver
Features
Description

Internal 550V Power MOSFET
The WS3412 is a high precision non-isolated buck driver

Active PFC for High Power Factor and Low THD
with active PFC, specially designed for universal input offline

Critical Conduction Mode Operation
constant current LED lighting. The driver with on-chip PFC

System Efficiency up to 95%
circuit achieves high power factor and low THD. Operating in

Without auxiliary winding
critical conduction mode, the power MOSFET switching loss

Excellent Line and Load Regulation
is reduced and the inductor is fully utilized.

±3% LED Output Current Accuracy

Thermal Regulation Function
few external components, the LED output current can be

LED Short/Open Protection
precisely controlled.

Current Sensing Resistor Open Protection

Auto Fault Recovery
the system reliability, including LED open circuit protection,

Available in SOP8 Package
LED short circuit protection, CS resistor open circuit
The WS3412 integrates a 550V power MOSFET. With
The WS3412 offers rich protection functions to improve
protection and cycle by cycle current limit. All the protection
functions are auto-recovery. The system reliability is further
Applications
improved by the thermal regulation function. The output

E27 LED Bulb, Spot Light

PAR30, PAR38 Lamp

T8/T10 LED String

Other LED Lighting
current is reduced when the driver is over temperature.
The WS3412 has ultra low start up current and ultra low
operating current.
The WS3412is available in SOP8 Package
Typical Application
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WS3412 ProductDescription
Pin Configuration and Marking Information
The WS3412 is available in SOP8 Package,the top marking is shown as below:
WS3412S8P
A:Product Code
X:Internal Code
BCY:Internal Code For QC
YMX:D/C
Pin Definition
Name
Pin No.
Description
COMP
1
GND
2
Ground.
VCC
3
Power Supply Pin. Connect a bypass capacitor from this pin to GND.
FB
4
D
5/6
Internal HV Power MOSFET Drain.
CS
7/8
Current Sense Pin. Connect a resistor to GND to sense the inductor current.
Loop Compensation Node. This pin connects a capacitor to GND for stabilization of the
control loop, achieving accurate LED current, high Power Factor and low THD.
Feedback Voltage Input Pin. This pin detects the inductor demagnetization signal and the
output voltage.
Internal Block Diagram
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WS3412 ProductDescription
Ordering Information
Package
8-Pin SOP-8,
Pb-free
Marking
Part Number
WS3412S8P
WS3412S8P
Recommended Operation Conditions
Part Number
Package
WS3412S8P
SOP8
Input voltage
Maximum output
power
175VAC-264VAC
120V/170mA
90VAC-264VAC
80V/170mA
Absolute Maximum Ratings
symbol
paramete
Range
unit
VCC
Vcc pin voltage
-0.3~8
V
VD
Internal HV MOSFET Drain to Source voltage
-0.3~550
V
VCS
Current sense pin input voltage
-0.3~7
V
VFB
Feedback pin input voltage
-0.3~7
V
VCOMP
Compensation pin voltage
-0.3~7
V
PDMAX
Power dissipation
0.5
W
TJ
Operating junction temperature
165
℃
TSTG
Storage temperature range
-55~165
℃
Note : Stresses beyond those listed under “absolute maximum ratings” may cause permanent damage to the device.
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WS3412 ProductDescription
Electrical Characteristics (Unless otherwise specified, VCC=8V and TA =25 ℃)
Symbol
Parameter
Conditions
Min
Typ
Max
7.5
8.0
8.5
Units
Supply Voltage Section
Vcc_clamp
VCC Clamp Voltage
Icc_clamp
VCC Clamp Current
VCC_ST
VCC Turn On Threshold
VCC Rising
Vuvlo_HYS
VCC Turn Off hysteresis
VCC Falling
1.32
Ist
VCC Startup Current
VCC<VCC_ST-0.5V
70
Iop
VCC Operating Current
5
7.07
V
mA
7.57
8.07
V
V
100
uA
400
uA
1
V
350
ns
200
ns
Current Sense Section
Over current
Vocp
TLEB
Protectionthreshold
Leading Edge Blanking Time
for Current Sense
Td
Switch off Delay Time
Compensation Section
VREF
Internal Reference Voltage
194
200
206
mV
VCL
COMP Low Clamp Voltage
1.5
V
VCH
COMP High Clamp Voltage
4
V
Internal driver
TOFF_MIN
Minimum Off Time
3
us
TON_MAX
Maximum On Time
20
us
1.6
V
0.2
V
Feedback Section
VFB
FB Over Voltage Protection
Threshold
FB Falling Edge
VZCD
Threshold Voltage
Power MOSFET
RDSON
VDS
Static Drain-source
5.5
On-resistance
Drain-Source Breakdown
6.9
550
Voltage
Ω
V
Thermal Regulation Section
TREG
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Thermal Regulation
Temperature
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℃
150
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WS3412 ProductDescription
Application Information
RFBL
1.6V

RFBL  RFBH VOVP
The WS3412 is a high precision Active PFC driver
integrating 550V power MOSFET, specially designed for
non-isolated buck offline constant current LED lighting.
Where,
Operating in critical conduction mode, the driver achieves
RFBL: The lower resistor of the feedback network
high power factor, low THD and high efficiency.
RFBH: The upper resistor of the feedback network
VOVP: Output over voltage setting point
Start Up
The minimum VOVP should be set about 1.3Vo.It is
After system powered up, the VCC pin capacitor is
charged up by the start up resistor. When the VCC pin
recommended that the FB lower resistor is set to
3.3KΩ—5.1KΩparalleled with a 22pF ceramic capacitor.
voltage reaches the turn on threshold, the internal circuits
start working. The COMP pin voltage is pulled up to 1.5V
Protection Functions
quickly, then the WS3412starts switching. The system works
at 10k Hz frequency at the beginning, the COMP voltage
The WS3412 offers rich protection functions to improve
the system reliability.
rises up gradually, and the inductor peak current also rises
When the LED is open circuit, the output voltage will
up. The LED current hence achieves a soft start without
gradually rise up. The output voltage is sensed by the FB pin
overshoot. After the output voltage is built up, the VCC
when power MOSFET is turned off. When FB voltage
power is supplied by the output voltage through a diode.
reaches the OVP threshold, it will trigger fault logic and the
The maximum value of the startup current is 100uA. For
system stops switching.
the application of 85VAC—264VAC, the startup resistor can
be calculated by the equation:
Rst 
Vin _ min
I st _ max
When the LED is shorted circuit, the system will work
under 10k Hz switching frequency. Meanwhile, the output
voltage is low and the VCC pin cannot be charged up by the
85V

 850 KΩ
100uA
output voltage, so the VCC pin voltage will gradually
decrease and finally reaches the UVLO threshold.
After the system enters into fault condition, the VCC
voltage will decrease until it reaches UVLO threshold. Then
Constant Current Control
The WS3412 utilizes floating ground structure. The
inductor current is sensed during the whole switching cycle,
the system will re-start again. If the fault condition is
removed, the system will resume normal operation.
When the output is short circuit or the inductor is
thus it achieves high precision output current control and
saturated, the CS peak voltage will be relatively high. When
also excellent line and load regulation.
The current in LED can be calculated by the equation:
CS voltage reaches the internal limitation (1V), the power
MOSFET will be turned off instantaneously. This cycle by
V
200mV
I O  CS 
RCS
Rcs
cycle current limitation can help protecting the power
MOSFET, the inductor and the output diode.
Rcs is the current sensing resistor.
Thermal Regulation
The WS3412 integrates thermal regulation function.
Feedback Network
When the system is over temperature, the output current is
The WS3412 senses the output current zero crossing
information through the feedback network, the FB falling
threshold voltage is set to 0.2V with 0.15V hysteresis. The
FB pin is also used to detect output OVP, the threshold
gradually reduced; the output power and thermal dissipation
are also reduced. The system temperature is regulated and
the system reliability is improved. The thermal regulation
temperature is set to 150℃ internally.
voltage is 1.6V. The ratio of FB upper resistor to lower
resistor can be set as:
PCB Layouts
The following guidelines should be followed in WS3412
PCB layout:
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WS3412 ProductDescription
Bypass Capacitor
FB Pin
The bypass capacitor on VCC pin should be as close as
The feedback resistor divider should be as close as
possible to the VCC and GND pins.
possible to the FB pin, and the trace must keeps away from
Ground Path
dynamic node of the inductor (DRAIN pin trace、the positive
The power ground path for current sense resistor
pin and the negative pin of Vo trace), otherwise the FB pin
should be short and wide, and it should be as close as
OVP function might have risk to be mis-triggered by the
possible to the IC ground (pin 2), otherwise the LED output
system noise.
current accuracy maybe affected. The IC signal ground for
DRAIN Pin
COMP and FB components should be connected to the IC
To increase the copper area of DRAIN pin for better
GND pin with short traces and should be away from the
thermal dissipation. However, too large copper area may
power ground path.
compromise EMI performance.
The Area of Power Loop
The material of PCB
The area of main current loop should be as small as
Avoid choosing the material that is easy to absorb the
possible to reduce EMI radiation.
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moisture, just like paper copper-clad laminates.
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WS3412 ProductDescription
Package Information
SOP8Package Outline Dimensions
B2
A1
A2
0.5* 0.125± 0. 05
球形标记
D
D1
B
B1
A
C4
A3
R2
θ4
C
C1
C2
θ2
C3
R1
θ1
θ3
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Symbol
Dimensions in Millimeters
Dimensions in Inches
Min
Max
Min
Max
A
4.70
5.10
0.185
0.201
B
3.70
4.10
0.146
0.161
C
1.30
1.50
0.051
0.059
A1
0.35
0.48
0.014
0.019
A2
1.27TYP
0.05TYP
A3
0.345TYP
0.014TYP
B1
5.80
B2
6.20
0.228
5.00TYP
0.244
0.197TYP
C1
0.55
0.70
0.022
0.028
C2
0.55
0.70
0.022
0.028
C3
0.05
0.225
0.002
0.009
C4
0.203TYP
0.008TYP
D
1.05TYP
0.041TYP
D1
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WS3412 ProductDescription
NOTE:
1.We strongly recommend customers check carefully on the trademark when buying our product, if there is any
question, please don't be hesitate to contact us.
2.Please do not exceed the absolute maximum ratings of the device when circuit designing.
3.Winsemi Microelectronics Co., Ltd reserved the right to make changes in this specification sheet and is
subject to change without prior notice.
CONTACT:
Winsemi Microelectronics Co., Ltd.
ADD:Futian District, ShenZhen Tian An Cyber Tech Plaza two East Wing 1002
Post Code : 518040
Tel : +86-755-8250 6288
FAX : +86-755-8250 6299
Web Site : www.winsemi.com
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