20160322030536 2486

WS3442 ProductDescription
Non-isolated Buck Offline LED Driver
Features
Description

Critical Conduction Mode Operation
The WS3442 is a high precision buck constant current

Internal 500V Power MOSFET
LED driver. The device operates in critical conduction mode

No Auxiliary Winding
and is suitable for 85Vac~265Vac universal input offline LED

Ultra Low Operating Current
lighting.

±3% LED Output Current Accuracy

Efficiency up to 93%
operating current of the IC is very low. So it doesn’t need the

LED Open Protection
auxiliary winding for supplying the chip. It can achieve

LED Short Protection
excellent constant current performance with very few external

Current Sensing Resistor Short Protection
components, so the system cost and size are minimized.

Thermal Regulation Function

Available in SOP-8 Package and DIP-7 Package
The WS3442 integrates a 500V power MOSFET. The
The WS3442 utilizes patent pending current control
method. It can achieve precise output current and excellent
line regulation. The driver operates in critical conduction
mode, the output current does not change with the inductance
Applications
and LED output voltage.

LED Candle Light
The WS3442 offers rich protection functions to improve

LED Bulb, Spot Light
the system reliability, including LED open circuit protection,

T8/T10 LED String
LED short circuit protection, VCC under voltage protection,

Other LED Lighting
CS resistor short circuit protection and thermal regulation
function.
The WS3442 is available in SOP-8 Package and DIP-7
Package.
Typical Application(SOP-8 Package)
Attention:A 22pF capacitor can be parallel with Rovp and a resistor can be parallel with the Vcc capacitor.
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WS3442 ProductDescription
Typical Application(DIP-7 Package)
Attention:A 22pF capacitor can be parallel with Rovp and a resistor can be parallel with the Vcc capacitor.
Pin Configuration and Marking Information
The WS3442 is available in SOP-8 Package and DIP-7 Package,the top marking is shown as below:
WS3442S8P
A:Product Code
X:Internal Code
BCY:Internal Code For QC
YMX:D/C
WS3442D7P
A:Product Code
X:Internal Code
BCY:Internal Code For QC
YMX:D/C
Pin Definition
Name
Pin No.
Description
GND
1
Ground
ROVP
2
Over Voltage Protection Setting Pin. Connect a resistor to GND
NC
3
No Connection. Should be connected to GND(Pin1)
VCC
4
Power Supply Pin
DRAIN
5/6
Internal HV Power MOSFET Drain.
CS
7/8
Current Sense Pin. Connect a sense resistor between this pin and GND pin.
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WS3442 ProductDescription
Internal Block Diagram
Ordering Information
Package
Marking
Part Number
8-Pin SOP-8,
Pb-free
WS3442S8P
WS3442S8P
7-Pin DIP-7,
Pb-free
WS3442D7P
WS3442D7P
Recommended Operation Conditions
Part Number
Package
Input voltage
175VAC-264VAC
WS3442S8P
SOP8
90VAC-264VAC
WS3442D7P
175VAC-264VAC
DIP7
90VAC-264VAC
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Maximum output
power
80V/280mA
120V/220mA
80V/220mA
60V/300mA
120V/280mA
160V/220mA
80V/300mA
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WS3442 ProductDescription
Absolute Maximum Ratings
symbol
paramete
Range
unit
VDS
Internal HV MOSFET drain voltage
-0.3~500
V
ICC_MAX
VCC pin maximum sink current
2.5
mA
VROVP
Over-voltage setting pin voltage
-0.3~7
V
VSOURCE
Internal HV MOSFET source voltage
-0.3~8
V
VCS
Current sense pin input voltage
-0.3~7
V
PDMAX
Power dissipation SOP8
0.6
W
PDMAX
Power dissipation
0.9
W
DIP7
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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WS3442 ProductDescription
Electrical Characteristics (Unless otherwise specified, VCC=7V and TA =25 ℃)
Symbol
Parameter
Conditions
Min
Typ
Max
Units
Supply Voltage Section
Vcc_clamp
VCC Clamp Voltage
Ivcc=1mA
7.3
V
Icc_clamp
VCC Clamp current
VCC_ST
VCC Turn On Threshold
VCC Rising
6.9
V
Vuvlo_HYS
VCC Turn off Hysteresis
VCC Falling
1.5
V
Ist
VCC Startup Current
VCC<VCC_ST-0.5V
230
Iop
VCC Operating Current
2.5
270
200
mA
uA
uA
Current Sense Section
Vcs_th
TLEB
Threshold Voltage for Peak
390
Current Limit
Leading Edge Blanking Time
for Current Sense
TDELAY
Switch Off Delay Time
400
410
mV
350
ns
300
ns
Internal Time Control Section
TOFF_MIN
Minimum OFF Time
3
us
TOFF_MAX
Maximum OFF Time
340
us
TON_MAX
Maximum On Time
53
us
MOSFET Section
Static Drain-source
RDSON
VDS_BD
Vcc=7V/Id=0.5A
On-resistance
Drain-Source Breakdown
Vgs=0V/Id=250uA
Voltage
Power MOSFET Drain
Idss
Leakage Current
4.8
6
500
ohm
V
Vgs=0V/Vds=500V
10
uA
ROVP section
VROVP
ROVP Pin Voltage
0.5
V
160
℃
20
℃
150
℃
Thermal Regulation Section
TSD
TSD_HYS
T_comp
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Thermal Shutdown
Temperature
Thermal Shutdown Hysteresis
Thermal Regulation
Temperature
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WS3442 ProductDescription
Application Information
t on 
The WS3442 is a high performance non-isolated Buck
converter specially designed for LED lighting. The device
L  IPK
VIN  VLED
integrates a 500V power MOSFET. With very few external
Where,
components, the converter achieves excellent constant
L is the inductance value
current control. And it does not need auxiliary winding for
VIN is the DC bus voltage after the rectifier bridge
powering the IC or voltage sensing, hence the system size
VLED is the voltage on the LED
and cost is greatly reduced.
After the power MOSFET is switched off, the current in
the inductor decreases. When the inductor current reaches
Start Up
zero, the power MOSFET is turned on again by IC internal
After system powered up, the VCC pin capacitor is
logic. The off time of the MOSFET is given by:
charged up by the start up resistor. When the VCC pin
t off 
voltage reaches the turn on threshold, the internal circuits
start operating. The WS3442 integrates a 17V zener diode
to clamp the VCC voltage. Due to the ultra-low operating
The inductance can be calculated by the equation:
current, the auxiliary winding is not needed to supply the IC.
L
The maximum value of the startup current is 270uA. For
the application of 176VAC — 264VAC, the startup resistor
can be be calculated by the equation:
Rst 
Vin _ min  1.414
I st _ max
L  IPK
VLED
VLED  (VIN  VLED )
f  IPK  VIN
The f is the system switching frequency, which is
176V  1.414

 920k
270uA
proportional to the input voltage. So the minimum switching
frequency is set at lowest input voltage, and the maximum
switching frequency is set at highest input voltage.
The minimum and maximum off time of WS3442 is set
at 3us and 340us, respectively. Referring to the equation of
Constant Current Control
Cycle by Cycle current sense is adopted in WS3442,
Toff calculation, if the inductance is too small, the Toff may
the CS pin is connected to the current sense comparator,
be smaller than the minimum off time, system will operate in
and the voltage on CS pin is compared with the internal
discontinuous conduction mode and the output current will
400mV reference voltage. The MOSFET will be switched off
be smaller than the designed value. If the inductance is too
when the voltage on CS pin reaches the threshold. The CS
large, the Toff may be larger than the maximum off time, the
comparator includes a 350ns leading edge blanking time.
system will operate in continuous conduction mode and the
output current will be higher than the designed value. So it is
The peak inductor current is given by:
I PK
important to choose a proper inductance.
400

( mA )
R CS
Over Voltage Protection
The over voltage protection can be programmed by the
Where, RCS is the current sense resistor value.
The current in LED can be calculated by the equation:
I LED 
ROVP pin resistor. The ROVP pin voltage is 0.5V.
When the LED is open circuit, the output voltage
I PK
2
increases gradually, and the demagnetization time gets
shorter. The demagnetization time at OVP---- Tovp can be
Where, IPK is the peak current of the inductor.
calculated by the open circuit protection voltage:
Inductor Selection
Tovp 
The WS3442 works under inductor current critical
conduction mode. When the power MOFET is switched on,
L  Vcs
Rcs  Vovp
the current in the inductor rises up from zero, the on time of
Where,
the MOSFET can be calculated by the equation:
Vcs is the CS pin turn off threshold (400mV)
Vovp is the open circuit protection voltage
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WS3442 ProductDescription
And then the Rovp resistor value can be calculated by
PCB Layouts
the equation:
The following rules should be followed in WS3442 PCB
Rovp  3.3* Tovp *106
layout:
(kohm)
Vcc Capacitor
The bypass capacitor on VCC pin should be as close as
Protection Function
possible to the VCC Pin and GND pin.
The WS3442 offers rich protection functions to improve
ROVP Pin
the system reliability, including LED open/short protection,
CS resistor short protection, VCC under voltage protection,
The ROVP resistor should be as close as possible to
the ROVP Pin.
thermal regulation. When the LED is open circuit, the
Ground Path
system will trigger the over voltage protection and stop
The power ground path for current sense should be
switching.
short, and the power ground path should be separated from
When the LED short circuit is detected, the system
works at low frequency (5kHz), and the CS pin turn off
small signal ground path before connecting to the negative
node of the bulk capacitor.
threshold is reduced to 200mV. So the system power
The Area of Power Loop
consumption is very low. At some catastrophic fault
The area of main current loop should be as small as
condition, such as CS resistor shorted or inductor saturated,
possible to reduce EMI radiation, such as the inductor, the
the internal fast fault detection circuit will be triggered, the
power MOSFET, the output diode and the bus capacitor
system stops switching immediately.
loop.
After the system enters into fault condition, the VCC
NC pin
voltage will decrease until it reaches the UVLO threshold,
The NC pin should be connected to GND (pin1).
then the system will re-start again. If the fault condition is
Drain Pin
removed, the system will recover to normal operation.
To increase the copper area of DRAIN pin for better
thermal dissipation. However too large copper area may
Thermal Regulation
compromise EMI performance.
The WS3442 integrates thermal regulation function.
The material of PCB
When the system is over temperature, the output current is
gradually reduced; the output power and thermal dissipation
Avoid choosing the material that is easy to absorb the
moisture, just like paper copper-clad laminates.
are also reduced. The system temperature is regulated and
the system reliability is improved. The thermal regulation
temperature is set to 150℃ internally.
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WS3442 ProductDescription
Package Information
SOP8 Package 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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Dimensions in Millimeters
Symbol
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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WS3442 ProductDescription
DIP7 Package Outline Dimensions
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Dimensions in Millimeters
Symbol
Dimensions in Inches
Min
Max
Min
Max
A
9.00
9.50
0.354
0.374
B
6.10
6.60
0.240
0.260
C
3.0
3.4
0.118
0.134
A1
1.474
1.574
0.058
0.062
A2
0.41
0.53
0.016
0.021
A3
2.44
2.64
0.096
0.104
A4
0.51TYP
0.02TYP
A5
0.99TYP
0.04TYP
C1
6.6
C2
7.30
0.260
0.50TYP
0.287
0.02TYP
C3
3.00
3.40
0.118
0.134
C4
1.47
1.65
0.058
0.065
D
7.62
9.3
0.300
0.366
D1
0.24
0.32
0.009
0.013
D2
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WS3442 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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