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WS3254 Product Description
High Precision Primary-Side Off-line PWM Power Switch
Features
� 5uA ultra-low startup current
� 2mA Low operating current
� ±5% Constant Voltage Regulation at Universal AC input
� Primary-side Sensing and Regulation Without TL431
�
�
�
�
�
�
�
WS3254 operates in primary-side sensing and regulation.
Consequently, optocoupler and TL431 could be eliminated,
thus reduce the cost.
It can achieve ±5% constant voltage precision in full input
voltage range. CC/CV Control as shown in fig.1. In CC
and Opto-coupler
Control, the current and output power setting can be adjusted
Programmable CV and CC Regulation
externally by the sense resistor Rs at CS pin. In CV control,
Built-in Primary winding inductance compensation
multi-mode
Programmable cable drop compensation
performance and high efficiency. In addition, good load
Built-in soft start
regulation is achieved by the built-in cable drop compensation.
Built-in Leading-edge blanking
Device operates in PFM in CC mode as well at large load
Cycle by cycle over current protection (OCP)
condition and it operates in PWM with frequency reduction at
VCC
over
voltage
clamp
&
under
voltage
are
utilized
to
achieve
high
light/medium load.
Vo
lockout( UVLO)
�
�
�
operations
Maximum Gate output voltage clamped at 12V
5%
Frequency jittering
Ultra low standby power (<100mW)
Applications
Io
Low power AC/DC offline SMPS for
�
Cell Phones/Cordless phones Charger
�
Digital Cameras Charger
�
Small Power Adapter
WS3254 offers power on soft start control and protection
�
Auxiliary Power for PC, TV etc.
coverage with auto-recovery features
�
Linear Regulator/RCC Replacement
including Cycle-by-Cycle current limiting, VCC
Ic c
Fig.1 Typical CC/CV Curve
OVP, VCC clamp and UVLO. The gate-driven output is
clamped to maximum 12V to protect the internal MOSFET.
Excellent EMI performance is achieved by using the
General Description
WS3254 is a high-integrated offline PWM power switch,
optimized for high performance low power AC/DC charger
soft-switching
and
frequency
jittering
at
the
totem-pole-gate-drive output. The WS3254 is the ideal
substitute of the linear power supply or the RCC-mode power,
and adapter application.
for a better performance of the whole switch power system
and a lower cost.
WS3254 is available in DIP8 package.
W/T-D012-Rev.A/1 Jul.2013
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WS3254 Product Description
Typical Application Circuit
VO
CO
NS
NP
AC
NA U X
VCC
GND
COMP
GND
IN V
CS
RS
G ra in
G ra in
W S3 2 5 4
n Definition and Device Marking
Pi
Pin
WS3254 is available in DIP8 package:
VCC
COMP
IN V
1
8
2
7
3
D IP 8
D: DIP8
GND
A:wafer information;
GND
WS3254D8P
A1a
2C
6
D R A IN
4
5
CS
P: no Pb
1:Ver.; a: Package Code
2C:Y+M(2=2012 C=12 Month
D R A IN
(1,2…A=10,B=11,C=12)
Pin Function Description
Pin
Name
Pin
Number
VCC
1
Power
Power supply
COMP
2
Loop
Compensation
Loop Compensation for CV Stability
INV
3
Feedback Input
CS
4
DRAIN
5/6
Current
Monitoring
Power transistor
drain
GND
7/8
Pin Type
GND
Function Description
The voltage feedback from auxiliary winding. Connected to resistor
divider from auxiliary winding reflecting output voltage. PWM duty cycle
is determined by EA output and current sense signal at pin4.
Current sense input.
This pin connects directly to the primary lead of the transformer.
Ground
W/T-D012-Rev.A/1 Jul.2013
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WS3254 Product Description
Block Diagram
vcc
1
UVLO
5V
POR
D R A IN
Insernal
S u p p ly
5 /6
G a te
Driver
Po we r
M O SF ET
CC
Controller
Soft start
PW M
Generator
D ro p
Com p
OCP
2V
CLK
Genterator
EA
IN V
Sampler
3
CS
4
LEB
Sa mp lin g
Co n tro lle r
Frequency
Shuffling
GND
7 /8
COMP
2
Output Power Table
230VAC±15%
85-264VAC
Adapter1
Adapter1
12W
8W
Product
WS3254
Note
Note: Maximum practical continuous power in an Adapter design with sufficient drain pattern as a heat sink, at 50℃ ambient.
Ordering Information
Package
IC Marking Information
Purchasing Device Name
8-Pin DIP-8, Pb-free
WS3254D8P
WS3254D8P
Recommended Operating Condition
Symbol
Parameter
Value
Unit
VCC
VCC supply voltage
10~30
V
TA
Operating temperature
-20~85
℃
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WS3254 Product Description
Absolute Maximum Ratings
Symbol
Drain voltage(off-state)
VCC
VINV
VCS
VCOMP
TJ
TSTG
ICC
Parameter
Value
Unit
Drain Voltage (off state)
DC supply voltage
INV input voltage
CS input voltage
COMP input voltage
Max. Operating junction temperature
Min./Max. Storage temperature
VCC Clamp Continuous Current
-0.3~600
30
-0.3~7
-0.3~7
-0.3~7
150
-55~150
10
V
V
V
V
V
℃
℃
mA
Note
Note: Stresses above those listed under Absolute Maximum Ratings may cause permanent damage to the device. These are
stress ratings only, functional operation of the device at these or any other conditions beyond those indicated in the
Recommended Operating Conditions section are not implied. Exposure to absolute maximum-rated conditions for extended
periods may affect device reliability.
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WS3254 Product Description
Electrical Characteristics (TA=25℃,VCC=16V, if not otherwise noted)
Supply Voltage (VCC)
symbol
parameter
Test condition
I_VCC_ST
Start up current
I_VCC_OP
Typ
Max
Unit
VCC=13V
5
20
uA
Operation Current
VCC=18V,INV=2V,CS=0V
2
3
mA
UVLO_ON
Turn on threshold Voltage
VCC falling
8.2
9.0
10.5
V
UVLO_OFF
Turn-off threshold Voltage
VCC rising
13.5
14.8
16.0
V
VCC_Clamp
VCC Zener Clamp Voltage
IVCC=10mA
28
29
31
V
OVP
Over
voltage
Threshold
Ramp VCC until gate shut down
27
28.3
30
V
1.935
1.975
2.015
V
protection
Min
Error Amplifier Section
Vref_EA
Reference voltage for EA
Gain
DC gain of EA
I_comp_max
Max.
Cable
current
compensation
INV=2V,COMP=0V
60
dB
37.5
uA
625
ns
Current Sense Section
TLEB
Leading edge Blanking Time
Zsense
Input impedance
TD_OC
OCP control delay
VTH_OC
OCP threshold
T_ss
Soft start time
50
kΩ
110
0.895
0.91
ns
0.925
17
V
ms
Oscillator Section
Freq_Max
IC Maximum frequency
60
Freq_Nom
System nominal switch frequency
Freq_startup
INV=0V,COMP=5V
∆f/Freq
Frequency shuffling range
67.5
75
khz
60
khz
14
khz
±6
%
MOSFET Section
MOSFET Drain-Source
breakdown voltage
Static Drain to Source on
resistance
BVdss
Ron
600
V
10
Ω
Note
Note: 1. Freq_Max indicates IC internal maximum clock frequency. In system application, the maximum operation frequency of
67.5 kHz nominal occurs at maximum output power or the transition point from CV to CC.
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WS3254 Product Description
Typical Operating Characteristics
UVLO (OFF ) (V )vs Temperature ( C )
UVLO (ON ) ( V ) vs Temperature ( C )
O
O
UVLO( OFF )( V )
UVLO ( ON )( V)
1 0 .5
1 0 .0
9 .5
9 .0
8 .5
8 .0
7 .5
-4 0
20
-1 0
50
80
1 6 .5 0
1 5 .5 0
1 5 .0 0
1 4 .5 0
1 4 .0 0
1 3 .5 0
1 3 .0 0
-4 0
11 0
-1 0
20
50
11 0
80
Temperature ( C )
O
Temperature ( C )
O
Istarup ( uA ) vs Temperature ( C )
O
Freq_Max ( kHz )vs Temperature ( C )
7 0 .0
Istarup ( uA )
Freq_Max ( kHz )
O
6 5 .0
6 0 .0
5 5 .0
3 .0
2 .5
2 .0
1 .5
1 .0
5 0 .0
-4 0
20
-1 0
50
80
-40
11 0
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80
11 0
Temperature ( C )
O
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O
Temperature ( C )
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WS3254 Product Description
Function Description
output filter capacitor Co. The current in the primary winding
WS3254 is a high-integrated offline PWM power switch,
ramps up. When MOSFET turns off, the primary current
optimized for high performance low power AC/DC charger
transfers to the secondary at the amplitude of
and adapter application. WS3254 operates in primary-side
sensing and regulation. Consequently, opto-coupler and
Is =
NP
*Ip
Ns
TL431 could be eliminated, thus reduce the cost. High
precision CC/CV control can meet most adapter and charger
The auxiliary voltage reflects the output voltage, given by
N AUX
* (Vo + ∆V )
NS
application requirements.
V AUX =
Startup Current and Startup Control
Where △V indicates the drop voltage of the output Diode.
Startup current of WS3254 is designed to be extremely low at
Via a resistor divider connected between the auxiliary
5uA, so that VCC could be charged up above UVLO
winding and INV, the auxiliary voltage is sampled at the end
threshold level and device starts up quickly. A large value
of the demagnetization and it is hold until the next sampling.
startup resistor can therefore be used to minimize the power
The sampled voltage is compared with Vref (2V) and the
loss, predigest the design of startup circuit and provides
error is amplified. The error amplifier output COMP reflects
reliable startup in application.
the load condition and controls the PWM switching
frequency to regulate the output voltage, thus the constant
Operating Current
output current can be achieved.
The operating current of WS3254 is low at 2mA. Excellent
When sampled voltage is below Vref and error amplifier
efficiency is achieved with low operating current together and
output COMP reaches its maximum, the switching frequency
multi-mode control circuit.
is controlled by the sampled voltage thus the output voltage
to regulate the output current, thus the constant output
CC/CV Operation
current can be achieved.
WS3254 is designed to produce good CC/CV control
characteristic as shown in the fig.1. In charger applications, a
Adjustable CC point and Output Power
discharged battery charging starts in the CC portion of the
In WS3254, the CC point and maximum output power can be
curve until it is nearly full charged and smoothly switches to
externally adjusted by external current sense resistor Rs at
operate in CV portion of the curve. In an AC/DC adapter, the
CS pin. The output power is adjusted through CC point
normal operation occurs only on the CV portion of the curve.
change. The larger Rs, the smaller CC point is, and the
The CC portion provides output current limiting. In CV
smaller output power becomes, and vice versa.
operation, the output voltage is regulated through the primary
Vo
side control. In CC operation mode, WS3254 will regulate the
Large R s
output current constant regardless of the output voltage drop.
Small R s
Principle of Operation
To achieve high precision CC/CV control, system needs to be
Io
designed in DCM mode for flyback system. In DCM mode, the
output voltage can be sensed via the auxiliary winding. During
Fig.2 Adjustable output power by changing Rs
MOSFET turn-on time, the load current is supplied from the
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WS3254 Product Description
Operation switching frequency
comparator is disabled and thus cannot turn off the internal
The switching frequency of WS3254 is adaptively controlled
MOSFET during the blanking period. PWM duty cycle is
according to the load conditions and the operation modes.
determined by the current sense input voltage and the EA
The operation switching frequency at maximum output power
output voltage.
is set to 67.5KHz internally. In DCM mode, the maximum
Programmable Cable Drop Compensation
output power is given by
PoMAX =
1
2
LP FSW I P
2
Cable drop compensation is implemented to achieve good
load regulation in WS3254. An offset voltage is generated at
Where Lp indicate the inductance of primary winding and Ip is
peak current of primary winding.
current is inversely proportional to the voltage across pin
The change of the primary winding inductance results in the
change of the maximum output power and constant output
current in CC mode. To compensate the change from
variations of primary winding inductance, the switching
frequency is locked by an internal loop such that the
switching frequency is
FSW =
INV by an internal current flowing into the resister divider. The
COMP, as a result, it is inversely proportional to the output
load current, thus the drop due to the cable loss can be
compensated.
As the load current decreases from full-load to no-load, the
offset voltage at INV will increase. It can also be programmed
by adjusting the resistance of the divider to compensate the
1
drop for various cable lines used.
2TDemag
Since TDemag is inversely proportional to the inductance, as a
result, the product Lp and Fsw is constant, thus the maximum
output power and constant current in CC mode will not
change as primary winding inductance changes. Up to ±10%
variation of the primary winding inductance can be
Gate Drive
The gate drive strength which is too weak leads to over switch
loss of MOSFET while too strong gate drive output
compromises in the over EMI. A good tradeoff between output
strength and dead time control is achieved through the design
of the built-in totem pole gate. The low standby dissipation
compensation.
and good EMI system design is easier to achieve through this
dedicated devise. For MOSFET gate protection, an internal
Frequency Shuffling
Excellent EMI performance is achieved by using frequency
12V clamp is added at higher than expected VCC input.
jittering in WS3254.
Protection Controls
Excellent system stability is achieved by the comprehensive
Current Sensing and Leading Edge Blanking
Cycle-by-Cycle current limiting is offered in WS3254. The
switch current is detected by a sense resistor into the sense
pin. An internal leading edge blanking circuit chops off the
sense voltage spike at initial MOSFET on state due to
snubber diode reverse recovery so that the external RC
filtering on sense input is no longer required. The current limit
protection of WS3254. Including Cycle-by-Cycle current
limiting (OCP), VCC Clamp, Under Voltage Lockout on VCC
(UVLO).
Device restarts when VCC voltage drops below UVLO limit. It
is clamped when VCC is higher than threshold value. The
power MOSFET is shut down when VCC drops below UVLO
limit and device enters power on start-up sequence thereafter.
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WS3254 Product Description
Package Information
DIP-8 Package Outline Dimensions
D2
θ1
C1
C
C4
θ2
C2
C3
θ3
D1
A2
A5
A3
A1
D
A4
B
A
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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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WS3254 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
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