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OB2338
High Performance Current Mode PWM Power Switch
GENERAL DESCRIPTION
OB2338 combines a dedicated current mode
PWM controller with a high voltage power
MOSFET. It is optimized for high performance, low
standby power, and cost effective off-line flyback
converter applications in sub 27W range.
OB2338 offers complete protection coverage with
automatic self-recovery feature including Cycle-
by-Cycle current limiting (OCP), over load
protection (OLP), over temperature protection
(OTP), over voltage protection and VDD under
voltage lockout (UVLO).
Excellent EMI
performance is achieved with On-Bright
proprietary frequency shuffling technique together
with soft switching control at the totem pole gate
drive output.
The tone energy at below 20KHZ is minimized in
the design and audio noise is eliminated during
operation.
OB2338 is offered in DIP8 package.
APPLICATIONS
Offline AC/DC flyback converter for
AC/DC adapter
PDA power supplies
Digital Cameras and Camcorder Adapter
VCR, SVR, STB, DVD&DVCD Player SMPS
Set-Top Box Power
Auxiliary Power Supply for PC and Server
Open-frame SMPS
TYPICAL APPLICATION
FEATURES
Level 5 compliance with < 100mW standby
power at universal AC input
Power on soft start reducing MOSFET Vds
stress
Frequency shuffling for EMI
Extended burst mode control for improved
efficiency and minimum standby power design
Audio noise free operation
Fixed 55KHZ (typical) switching frequency
Internal synchronized slope compensation
Low VDD startup current and low operating
current
Leading edge blanking on current sense input
Comprehensive protection coverage
o VDD under voltage lockout with hysteresis
(UVLO)
o Over temperature protection (OTP) with
auto- recovery
o On-Bright proprietary line input
compensated
o Cycle-by-Cycle over-current threshold
setting for constant output power limiting
over universal input voltage range.
o Accurate Overload protection (OLP).
o Over voltage protection(OVP)
o Secondary Rectifier Short Protection
Output Power Table
Product
OB2338
230VAC±15%
Open Frame1
27W
85-265VAC
Open Frame1
16W
Notes: 1. Maximum practical continuous power in an open frame design with sufficient drain pattern as a heat sink, at 50
ambient. Higher output power is possible with extra added heat sink or air circulation to reduce thermal resistance.
©On-Bright Electronics
Confidential
-1-
Preliminary Datasheet
OB_DOC_DS_233801

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OB2338
High Performance Current Mode PWM Power Switch
GENERAL INFORMATION
Pin Configuration
The OB2338 is offered in DIP8 package as shown
below.
Package Dissipation Rating
Package
RJA (/W)
DIP8
75
Note: Drain Pin Connected to 100mm2 PCB copper clad.
Ordering Information
Part Number Description
OB2338AP
DIP8, Pb-free
Absolute Maximum Ratings
Parameter
Drain Voltage (off state)
Value
-0.3V to BVdss
VDD Voltage
-0.3V to 30 V
VDD-G Input Voltage
-0.3V to 30 V
FB Input Voltage
-0.3 to 7V
Sense Input Voltage
-0.3 to 7V
Min/Max Operating Junction
Temperature TJ
Min/Max Storage
Temperature Tstg
Lead Temperature
(Soldering, 10secs)
-40 to 150
-55 to 150
260
Note: Stresses beyond 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
under “recommended operating conditions” is not implied.
Exposure to absolute maximum-rated conditions for extended
periods may affect device reliability.
OB2338 X X
Current Mode PWM Power Switch
Package
A:DIP8
Package Pb-free
P : Pb-free
Marking Information
©On-Bright Electronics
Confidential
-2-
Preliminary Datasheet
OB_DOC_DS_233801

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OB2338
High Performance Current Mode PWM Power Switch
TERMINAL ASSIGNMENTS
Pin Name
GND
FB
VDD-G
SENSE
VDD
Drain
I/O Description
P Ground
I
Feedback input pin. The PWM duty cycle is determined by voltage level into this pin
and the current-sense signal at Pin 4.
P Internal Gate Driver Power Supply
I Current sense input
P IC DC power supply Input
O
HV MOSFET Drain Pin. The Drain pin is connected to the primary lead of the
transformer
BLOCK DIAGRAM
VDD
3
Internal supply
LDO
RQ
S
UVLO POR
OVP
Burst
mode
RCeuferrreenntce OTP
Soft
Driver
VDD_G
2
Drain
5/6
Power
MOSFET
OSC
Extended
Burst mode
CPL Vth
Soft Start
OCP
Slope
compensation
SENSE
4
LEB
Internal supply
PWM Comparator
Debounce
OLP
7/8 GND
R FB
1
R
©On-Bright Electronics
Confidential
-3-
Preliminary Datasheet
OB_DOC_DS_233801

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OB2338
High Performance Current Mode PWM Power Switch
ELECTRICAL CHARACTERISTICS
(TA = 25, VDD=16V, unless otherwise noted)
Symbol
Parameter
Test Conditions
Min Typ Max Unit
Supply Voltage (VDD)
Istartup
VDD Start up Current
VDD=11V,Measure
Leakage current into VDD
5 20 uA
I_VDD_Operation Operation Current
VFB=3V
1.6 mA
UVLO(ON)
VDD Under Voltage
Lockout Enter
7.0 8.0 9.0 V
UVLO(OFF)
OVP(ON)
VDD Under Voltage
Lockout Exit (Recovery)
Over voltage protection
voltage
CS=0V,FB=3V Ramp up
VDD until gate clock is off
15.2
27.5
16.2
29
17.2
30.5
V
V
Feedback Input Section(FB Pin)
VFB_Open
VFB Open Loop Voltage
IFB_Short
FB pin short circuit
current
Short FB pin to GND and
measure current
4.9
5.5 6.1
0.35
V
mA
VTH_0D
VTH_PL
Zero Duty Cycle
Threshold Voltage
Power Limiting
Threshold Voltage
FB
FB
0.8 V
4.6 V
TD_PL
Power limiting Debounce
Time
ZFB_IN
Input Impedance
Current Sense Input(Sense Pin)
Soft start time
T_blanking
Leading edge blanking
time
50
15.7
mSec
Kohm
4 ms
270 ns
ZSENSE_IN
TD_OC
Input Impedance
Over Current Detection
and Control Delay
From Over Current Occurs
till the gate driver output
start to turn off
40
80
Kohm
nSec
VTH_OC
Internal Current Limiting
Threshold Voltage
FB=3.3V
0.72 0.77 0.82 V
Oscillator
FOSC
Normal
Frequency
Oscillation
50 55 60 KHZ
f_Temp
f_VDD
Frequency
Stability
Frequency
Stability
Temperature
Voltage
5%
5%
D_max
F_Burst
Maximum duty
cycle
Burst Mode
Frequency
FB=3.3V, CS =0V
Base
65 75 85 %
22 KHZ
Mosfet Section
BVdss
Rdson
MOSFET Drain-Source
Breakdown Voltage
Static Drain to Source On
Resistance
600 V
4.4 5.5 Ώ
Frequency Shuffling
f_OSC
Frequency Modulation
range /Base frequency
-4 4 %
Over temperature protection
Over temperature protection trip point
150
©On-Bright Electronics
Confidential
-4-
Preliminary Datasheet
OB_DOC_DS_233801

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OB2338
High Performance Current Mode PWM Power Switch
CHARACTERIZATION PLOTS
(The characteristic graphs are normalized at Ta=25)
UVLO(ON) vs Temperature
10
9
8
7
6
-40 -10 20 50 80 110 140
Temperature()
I_startup vs Temperature
5
4
3
2
1
0
-40 -10 20 50 80 110 140
Temperature()
Duty vs Vth_oc
1.05
1
0.95
0.9
0.85
0.8
0.75
0
10 20 30 40 50 60 70
Duty(%)
Rds(on) VS Temperature()
UVLO(OFF) vs Temperature
20
18
16
14
12
10
-40 -10 20 50 80 110 140
Temperature()
1000
800
600
400
200
0
0
VDD vs Iop_n(uA)
4 8 12 16 20 24 28
VDD(V)
Fosc vs Temperature
60
45
30
15
0
-40 -10 20 50 80 110 140
Temperature()
10
8
6
4
25 50 75 100 125 150
Temperature()
©On-Bright Electronics
Confidential
-5-
Preliminary Datasheet
OB_DOC_DS_233801