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WS3440 Product Description
Constant Current Controller For Non-isolated Buck LED Driver
General Description
Features
�
Inductor
Current
Critical
Mode,
No
Need
The WS3440 is a high precision constant current controller，
to
Compensate the Inductance Variation
designed for non-isolated buck LED driver. suitable for AC
Source Driver Structure, Not Need the Auxiliary
input voltage range (84V-264V)
Winding for VCC
The WS3440 uses high precision current sense circuit and
�
±3% LED Current Accuracy
patent method for constant current control, to achieve high
�
Up to 93% System Efficiency
precision output current and excellent line regulation. The
�
LED Short Circuit Protection
WS3440 operates in inductor current critical mode. The LED
�
Current Sense Resistor Short Circuit Protection
current is constant over wide range of inductance variation
�
Over Temperature Protection
and the LED output voltage, so the load regulation is
�
Programmable LED open protection
excellent.
�
The WS3440 uses patent source driver architecture. The
operation current is 200uA only, so the auxiliary winding is not
Applications
needed. It can simplify the system design and reduce the
�
LED Bulb
�
LED Candle light
�
LED Spot light
�
Decorative LED lighting
system cost.
The WS3440 offers rich protection functions, including LED
open/short circuit protection, current sense resistor short
circuit protection and over temperature protection.
Typical Application Circuit
AC
1 ROVP
6 VCC
3 CS
GND 2
G AT E 5
S
4
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WS3440 Product Description
Pin Definition and Device Marking
WS3440 is available in SOT23-6 package:
6
1
6
VCC
GND 2
5
G AT E
4
S
RO VP
CS
3
40:WS3440
Y: Year Code (0-9)
. 40 YMF
M: Month Code (1-12)
F:F: Factory No.
1
SO T23-6
Pin Function Description
Pin Name
Pin NO.
Description
ROVP
1
Programmable LED open protection pin，connect a resistor to GND
GND
2
Ground
CS
3
Current sense input, the sense resistor is connected from CS to ground
S
4
HV power MOSFET source
GATE
5
HV power MOSFET gate
VCC
6
Power supply
Block Diagram
GND
2
5 G AT E
So ft-Drive r
RO VP 1
In te r
su p p ly
UVLO
Z e ro -Cu rre n t
De te ct
L o g ic
&
d rive r
400m V
L in e
4 S
OCP
co mp e n sa tio n
L ED Sh o rt
CS Sh o rt
LED O PEN
VCC 6
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WS3440 Product Description
Ordering Information
Package
6-Pin SOT23-6,
Part Number
Marking
40 YMF
WS3440YP
Pb-free
Recommended Operating Condition
symbol
parameter
value
units
ILED
Output LED Current
< 300
mA
Absolute Maximum Ratings
symbol
parameter
Range
Units
ICC_MAX
VCC pin maximum sink current
2.5
mA
VROVP
ROVP input voltage
-0.3~7
V
VS
HV MOSFET source voltage
-0.3~8
V
VCS
Current sense pin input voltage
-0.3~7
V
Power dissipation
0.9
W
Operating junction temperature
150
℃
-55~150
℃
PDMAX
TJ
TSTG
Storage temperature range
Note: Stresses beyond those listed under “absolute maximum ratings” may cause permanent damage to the device. Under
“recommended operating conditions” the device operation is assured, but some particular parameter may not be achieved.
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WS3440 Product Description
Electrical Characteristics (Unless otherwise specified，TA=25℃，VCC=7V)
Symbol
Parameter
Conditions
Min
Typ
Max
Units
7.6
V
2.5
mA
7.2
V
Supply Voltage Section
Vcc_clamp
VCC Clamping Voltage
Icc_clamp
VCC Clamping Current
VCC_ST
VCC Start Up Voltage
7.0
VCC Rise
VCC Under Voltage
Vuvlo_HYS
VCC Falling
Latch Out Hysteresis
Ist
Start Up Current
Iop
Operation Current
6.6
7.3
6.9
1.5
VCC<VCC_ST-0.5V
45
V
60
200
uA
uA
Current Sensor Section
Current Sensor Voltage
Vcs_th
390
Threshold
400
410
mV
TLEB
Leading Edge Blanking
350
ns
TDELAY
Turn Off Delay Time
300
ns
Internal Driver Section
TOFF_MIN
Minimum Demagnetization Time
4
us
TOFF_MAX
Maximum Demagnetization Time
240
us
TON_MAX
Maximum Turn On Time
40
us
Internal reference voltage
0.5
V
ROVP Section
VROVP
Over Temperature Section
TSD
Thermal Shut Down Temperature
160
℃
TSD_HYS
Thermal Shut Down Hysteresis
20
℃
140
℃
Intelligent temperature compensation
T_comp
function
Drive ability Section
Imax
Built-in power tube maximum peak current
1.3
A
Note: Imax depends on the ambient temperature and cooling conditions chips work at high temperatures Imax will be reduced.
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WS3440 Product Description
Function Description
cost is low.
WS3440 is a constant current controller, designed for driving
non-isolated buck LED power supply. WS3440 uses patent
constant current control method and source driver structure,
Inductance Calculation
excellent constant current characteristic is achieved with low
counts components. Low cost and high efficiency of system
The WS3440 is designed to work in inductor current critical
is realized.
mode; the energy will be stored in the inductor when the
MOSFET is turned on. The turn on time is given by:
Start up
ton =
L × I PK
VIN − VLED
The Vcc will be charged through the startup resistor when
the system is powered on. When the voltage on Vcc reaches
the startup voltage threshold, the controller starts to
switching. The Vcc voltage of WS3440 is clamped to 7.3V
The L is the inductance. The Ipk is the peak current in
inductor. The VIN is the input rectified voltage. The VLED
is the voltage on LED.
When the power MOSFET is turned off, the inductor current
by internal Zener diode.
will decrease from the peak current to zero. The turn off time
Constant Current Control and Output Current Setting
is given by:
toff =
The WS3440 uses patent constant current control method,
excellent constant current is achieved with low counts
components. The WS3440 senses the peak current in
inductor cycle by cycle. The CS Pin is connected to the input
The MOSFET will be turned on again when it detects the
inductor current goes to zero. The inductance can be
calculated by the following equation:
of internal current comparator, and compared with the
internal 400mV reference voltage. The external power
L × I PK
VLED
L=
MOSFET will be turned off when the CS pin voltage reaches
VLED × (VIN − VLED )
f × I PK × VIN
the voltage threshold. The comparator has a 350ns LEB
The f is the system switching frequency, which is
timer to avoid mis-trigger.
proportional to the input voltage. So the minimum switching
The peak current in the inductor is given by:
frequency is set at lowest input voltage, and maximum
I PK
switching frequency is set at highest input voltage.
400
=
(mA)
RCS
The WS3440 internally set the minimum off time to 4us and
maximum off time to 240 us. When the inductance is very
The Rcs is the resistance of current sense resistor The
current in LED can be calculated by the following equation:
I LED
small, the toff may goes below the minimum off time and the
inductor current becomes discontinuous. So the output LED
I
= PK
2
current will be smaller than the setting value. If the
inductance is too large, the toff may goes beyond the
The IPK is the peak current in inductor
maximum off time and the inductor current becomes
Source Driver Structure
continuous. And the output LED current will be larger than
the setting value. So it’s very important to select a right
The WS3440 uses the patent source driver structure. The
inductance.
typical operation current is as low as 200uA, the auxiliary
The WS3440 also internally set the maximum on time to
winding is not need. So the system design is simple and the
40us. When the input voltage is very low or LED output
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WS3440 Product Description
voltage is very high, the ton may goes beyond the maximum
protection functions are designed to auto-recover. The over
on time. The power MOSFET will be turned off even the
temperature protection circuitry in the WS3440 monitors the
inductor current still below the setting value. So the output
die
LED current will be smaller than the setting value.
temperature rises to 150℃, the power MOSFET will be shut
junction
temperature
after
start
up.
When
the
down immediately and maintains at switch off condition until
Set open protection
the temperature on die falls 30℃ below the thermal
protection trigger point.
The LED open protection voltage can be set by adjusting the
PCB Layout
value of the resistor connecting from ROVP to GND.
In the LED open condition, the output voltage will raise
graduate, and the demagnetize time will shorten as well, the
The following guidelines should be followed in WS3440 PCB
demagnetize time Tovp can be calculator as below:
layout:
Tovp =
Bypass Capacitor
L × V CS
R CS × V OVP
The bypass capacitor on VCC pin should be as close as
possible to the VCC and GND pins.
In which the Vcs is the OCP threshold (0.4V) ,the Vovp is the
target output protection voltage. And the value of the resistor
Rovp is as below:
Ground Path
The power ground path for current sense should be short,
and the power ground path should be separated from small
Rovp = 15 * Tovp * 10
6
（KΩ）
signal ground path before the negative node of the bus
capacitor.
Protection Functions
The Area of Power Loop
The area of main current loop should be as small as
The WS3440 has many protection functions, including LED
open/short circuit protection, current sense resistor short
circuit protection and over temperature protection. All of the
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possible to reduce EMI radiation. And the controller should
be placed away from the heat generator, such as the power
diode.
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WS3440 Product Description
Package Information
SOT23-6 Package Outline Dimensions
U n it:m m
A
C2
B1
B
θ1
θ
B2
A2
R
θ3
C
D
R2
R1
C1
θ2
D2
A1
D1
D3
Winsemi
Dimensions in Millimeters
Symbol
Dimensions in Inches
Min
Max
Min
Max
A
2.72
3.12
0.107
0.123
B
1.40
1.80
0.055
0.071
C
1.00
1.20
0.039
0.047
A1
0.90
1.00
0.035
0.039
A2
0.30
0.50
0.012
0.020
B1
2.60
3.00
0.102
0.118
B2
0.119
0.135
0.005
0.005
C1
0.03
0.15
0.001
0.006
C2
0.55
0.75
0.022
0.030
D
0.03
0.13
0.001
0.005
D1
0.30
0.60
0.012
0.024
D2
0.25TYP
D3
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0.60
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0.024
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0.028
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WS3440 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:Room 1002, East, Phase 2, HighTech Plaza,Tian-An Cyber Park,Chegongmiao, FuTian, Shenzhen, P.R.
China.
Post Code : 518040
Tel : +86-755-8250 6288
FAX : +86-755-8250 6299
Web Site : www.winsemi.com
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