20160401090432 2820

WS9442P Product Description
Non-isolated Buck Offline LED Driver
Features
 Critical Conduction Mode Operation

Internal 500V Power MOSFET

Gate Drive and No Auxiliary Winding

±3% LED Current Accuracy

Efficiency up to 93%

LED Short Circuit Protection

LED Open Circuit Protection



Current Sense Resistor Short Protection
Description
The WS9442P is a high precision buck constant current LED
driver and is applied to non-isolated buck LED power system with
AC input voltage of 85VAC-265VAC. The WS9442P integrates a
500V power MOSFET, and can achieve excellent constant current
performance with very few external components, so the system
cost and size are minimized. The driver operates in critical
conduction mode, and the output current does not change with the
inductance and LED output voltage. The operating current of the
Thermal Regulation Function
IC is 200uA, so it doesn’t need the auxiliary winding for supplying
External PWM Dimming
the chip, thus simplify design and reduce cost.
The WS9442P adopts intelligent temperature control and
Applications
thoroughly solves the problem of LED flickering under high

LED Bulb Lights
temperature. It integrates an external dimming pin which inputs

LED Panel Lights
PWM signal and can dim by changing the duty cycle of the PWM

LED Strings
signal. The WS9442P offers full protection functions to improve
the system reliability, including LED open circuit protection, LED
short circuit protection, CS resistor short circuit protection and
thermal regulation function.
The WS9442P is available in DIP-7 Package.
Typical Application Circuit
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WS9442P Product Description
Pin Configuration and Marking Information
The WS9442P is available in DIP-7 Package. The top marking is shown as below:
WS9442PD7P:Product Code
A:Product Code
X:Internal Code
BCY:Internal Code For QC
YMX:D/C
Pin Definition
Pin No.
Name
Description
1
GND
2
ROVP
3
DIM
Dinmming Pin.Must be floated when not in use.
4
VCC
Power Supply Pin
5,6
DRAIN
7
CS
Ground
Over Voltage Protection Setting Pin. Connect a resistor to GND
Internal HV Power MOSFET Drain
Current Sense Pin. Connect a sense resistor between this pin and the GND
pin.
Block Diagram
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WS9442P Product Description
Ordering Information
Package
Marking
Part Number
7-Pin DIP-7, Pb-free
WS9442PD7P
WS9442PD7P
Recommended Operation Conditions
Part Number
Package
Input voltage
Maximum output power
120V/280mA
175VAC-264VAC
WS9442PD7P
160V/220mA
DIP7
90VAC-264VAC
80V/300mA
Absolute Maximum Ratings
Symbol
Parameter
Range
Unit
VDS
Internal HV MOSFET drain voltage
-0.3~500
V
ICC_MAX
VCC pin maximum sink current
10
mA
VROVP
LED open circuit protection voltage regulation
-0.3~7
V
VCS
Current sense pin input voltage
-0.3~7
V
PDMAX
Power dissipation DIP7
0.9
W
TJ
Maximum operating junction temperature
150
℃
TSTG
Minimum/Maximum Storage temperature
-55~150
℃
Note:Stresses beyond those listed under "absolute maximum ratings" may cause permanent damage to the device.
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WS9442P Product Description
Electrical Characteristics (Unless otherwise specified, VCC=15V and TA =25 ℃)
Symbol
Parameter
Conditions
Min
Typ
Max
Units
17.8
18.8
19.8
V
14
15
16.2
V
9
9.5
10
V
Supply Voltage Section
VCC_CLAMP
VCC Clamp Voltage
UVLO_on
Chip Start-up Voltage
10mA
VDD Under voltage
UVLO_off
protection
Ist
Startup Current
VCC= 13V
150
220
300
uA
Iop
Operating Current
Fop=70KHz
100
170
250
uA
390
400
410
mV
Current Sense Section
Threshold Voltage for
Vcs_th
Peak Current Limit
Leading Edge Blanking
TLEB
Time for Current Sense
TDELAY
Switch Off Delay Time
350
ns
200
ns
310
us
4.5
us
100
us
Internal Time Control Section
Toff_max
Minimum OFF Time
Toff_min
Maximum OFF Time
Ton_max
Maximum On Time
Rovp=70k
DIM Dimming Section
DIM Square Wave High
VH_DIM
Level
DIM Square Wave Low
VL_DIM
Level
DIM Square Signal
f_DIM
Frequency
1
3
5
V
-300
0
400
mV
0.1
0.5
5
KHZ
MOSFET Section
Static Drain-source
Rds_on
Vgs=15V,Ids=0.5A
On-State Resistance
Drain-Source Breakdown
BVdss
Voltage
Drain-Source Leakage
Idss
Vgs=0V,Ids=250uA
6.8
500
V
Vgs=0V,Vds=500V
Current
Ω
10
uA
Thermal Regulation Section
Thermal Regulation
TREG
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150
Temperature
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WS9442P Product Description
Function Description
adopted in WS9442P, the CS pin is connected to the current
The WS9442P is a high performance non-isolated buck
sense comparator, and the voltage on CS pin is compared
converter specially designed for LED lighting. The device
with the internal 400mV reference voltage. The MOSFET will
integrates a 500V power MOSFET. With the help of
advanced constant current control and gate drive technology,
be switched off when the voltage on CS pin reaches the
the
threshold. The CS comparator includes a 350ns leading edge
converter
achieves
excellent
constant
current
performance with very few external components. It does not
need auxiliary winding for powering the IC or voltage sensing,
blanking time.
The peak inductor current is calculated by the equation:
hence the system size and cost is greatly reduced.
I PK 
Start Up
After system powered on, the VCC pin capacitor is
400
(mA)
RCS
Where, Rcs is the current sense resistor value.
charged up by the start up resistor. When the VCC pin
The current in LED can be calculated by the equation:
voltage reaches the turn on threshold, the internal circuits
start operating. The WS9442P integrates a 17V ZENER
I LED 
diode to clamp the VCC voltage. Due to the ultra-low
operating current, the auxiliary winding is not needed to
supply the IC.
I PK
(mA)
2
Where, IPK is the peak current of the inductor.
The typical value of the start-up current is 200uA (the
maximum value is 300uA). For the application of 176VAC—
264VAC, the start-up resistor can be calculated by the
Freewheeling Diode
The diode will bear the reverse voltage equal to the input
equation:
voltage when the MOSFET is on. A 600V diode was
RST 
VIN _ MIN  1.414
I ST _ MAX

176  1.414
 820 K 
300
Two resistors in 1206 size SMD can be used in series.
suggested to use. Besides, the operating frequency of
freewheeling diode is from 20K to 120 KHz, such ultra fast
recovery diodes as ES and ER whose Trr is less than 50ns are
good choice.
VCC Capacitor Selection
The Vcc capacitor is used to bypass noise to IC, so that
Input Buck Electrolytic Capacitor
Input voltage should be considered in to the capacitor
to assure its stable operation, and should be as close as
pressure, and the common value is 400V.
possible to the chip.
In general, the capacitor design can be calculated by the
A 1uF capacitor can be used in Vcc. If selecting MLCC,
following empirical equations:
the material of X7R will be used to satisfy the stability of the
capacity under high temperature. Due to external damage
90Vac~264Vac: 1W output uses1uF buck electrolytic
capacitor;
resulted from small volume and brittle texture of MLCC, the
Vcc is easy to leakage currents, which will make the
176Vac~264Vac: 1W output uses 0.5uF buck electrolytic
capacitor.
WS9442P unable to start. Strict control measures are taken
in its layout and productive process.
Output Capacitor
Electrolytic capacitor is recommended to be used. Its
Constant Current Control
stable capacitance can improve the efficiency of power supply,
The WS9442P utilizes proprietary current control
the LED ripple current and luminous efficiency.
method. It can achieve precise LED output current with a few
external components. Cycle by Cycle current sense is
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Vovp voltage should be considered in output capacitor
pressure.
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WS9442P Product Description
Where, f is the maximum system switching frequency,
External PWM Dimming
which is proportional to the input voltage. So the minimum
The WS9442P integrates an external dimming pin which
inputs PWM signal and can dim by changing the duty cycle
switching frequency is set at lowest input voltage, and the
maximum switching frequency is set at highest input voltage.
of the PWM signal. The testing dimmable curve of a
The minimum and maximum off time of WS9442P is set at
120V/260mA driver under 175~264Vac application is shown
4.5us and 310us respectively. Referring to the equation of Toff
as below:
calculation, if the inductance is too small, the Toff may be
smaller than the minimum off time, the system will operate in
discontinuous conduction mode and the output current will be
smaller than the designed value. If the inductance is too large,
the Toff may be larger than the maximum off time, the system
will operate in continuous conduction mode and the output
current will be higher than the designed value. So it is
important to choose a proper inductance.
Thermal Regulation
The WS9442P integrates thermal regulation function.
The duty cycle of the PWM signal
When the system is under higher temperature, the output
current is gradually reduced; the output power and thermal
Inductor Selection
dissipation are also reduced. The system temperature is
The WS9442P works in a inductor critical current
conduction mode. When the power MOFET is switched on,
regulated and the system reliability is improved. The thermal
regulation temperature is set at 150℃ internally.
the current in the inductor rises up from zero. The on time of
Over Voltage Protection
the MOSFET can be calculated by the equation:
t on 
L  I PK
VIN  VLED
The over voltage protection of the WS9442P can be
programmed by the ROVP pin resistor. The ROVP pin voltage
is 0.5V.
Where,
When the LED is open circuit, the period of the output
L is the inductance value,
voltage increases gradually, the demagnetization time gets
IPK is the peak current of the inductor,
VIN is the DC bus voltage after the rectifier bridge,
shorter. The demagnetization time at OVP---- Tovp can be
calculated by the open circuit protection voltage by the
VLED is the voltage on the LED.
After the power MOSFET is switched off and the current
equation:
in the inductor decreases. When the inductor current reaches
Tovp 
zero, the power MOSFET is turned on again by IC internal
logic. The off time of the MOSFET is given by the equation:
toff 
L  I PK
VLED
Where,
Vcs is the CS pin turn off threshold (0.4V);
Vovp is the open circuit protection voltage.
The inductance can be calculated by the equation:
L
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And then the Rovp resistor value can be calculated by the
VLED  (VIN  VLED )
f  I PK  VIN
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equation:
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L  V CS
R CS  V OVP
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WS9442P Product Description
Rovp  120  7 . 67 * Tovp * 10 6 (KΩ)
PCB Layout
It is suggested that the open circuit protection voltage is
set at or above 1.5 times maximum load voltage.
The following rules should be followed in WS9442P PCB
layout:
VCC Capacitor: The VCC capacitor should be as close
Protection Function
The WS9442P offers full protection functions to improve
the system reliability, including LED open/short protection,
CS resistor short protection, VCC under voltage protection,
thermal regulation. When the LED is open circuit, the system
as possible to the VCC Pin and GND pin.
Ground Path: The power ground path for current sense
resistor should be short, and the power ground path should be
separated from small signal ground path before connecting to
the negative node of the bulk capacitor.
will trigger the over voltage protection and stop switching.
The Area of Power Loop: The area of main current loop
When the LED short circuit is detected, the system works at
should be as small as possible to reduce EMI radiation. And it
low frequency and the CS pin turn-off threshold is reduced.
should be away from diodes and other heating components.
So the system power consumption is very low. At some
ROVP PIN: The ROVP resistor should be as close as
abnormal fault condition, such as CS resistor shorted or
possible to the ROVP Pin to increase its resistance to prevent
inductor saturation, the internal fast fault detection circuit will
from the interference.
DRAIN PIN: The copper area of DRAIN pin can be
be triggered, the system stops switching immediately.
After the system enters into faulty condition, the VCC
voltage will decrease until it reaches the UVLO threshold,
increased for better thermal dissipation. And it should be away
from CS/VCC and ROVP Pin.
then the system will restart again. If the fault condition is
removed, the system will recover to normal operation.
Line Voltage Compensation
The WS9442P integrates line voltage compensation
function, which makes LED current remain unchanged in the
range of full voltage with good line regulation and current
accuracy.
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WS9442P Product Description
DIP7 Package Dimension
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Dimensions in Millimeters
Symbol
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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Dimensions in Inches
7.62TYP
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0.3TYP
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WS9442P Product Description
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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