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OB2273
High Performance Current Mode PWM Controller
GENERAL DESCRIPTION
OB2273 is a highly integrated current mode PWM
control IC optimized for high performance, low
standby power and cost effective offline flyback
converter applications.
PWM switching frequency at normal operation is
internally fixed and is trimmed to tight range. At no
load or light load condition, the IC operates in
extended ‘burst mode’ to minimize switching loss.
Lower standby power and higher conversion
efficiency is thus achieved.
VDD low startup current and low operating current
contribute to a reliable power on startup and low
standby design with OB2273.
OB2273 offers complete protection coverage with
auto-recovery including Cycle-by-Cycle current
limiting (OCP), over load protection (OLP), and
VDD under voltage lockout (UVLO). It also
provides the protections with latched shut down
including over temperature protection (OTP), and
over voltage (fixed or adjustable) protection (OVP).
Excellent EMI performance is achieved with On-
Bright proprietary frequency shuffling technique.
The tone energy at below 20KHZ is minimized in
the design and audio noise is eliminated during
operation.
OB2273 is offered in SOT23-6 and DIP-8 package.
FEATURES
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 65KHZ Switching Frequency
Comprehensive Protection Coverage
o VDD Under Voltage Lockout with
Hysteresis (UVLO)
o Cycle-by-cycle over current threshold
setting for constant output power limiting
over universal input voltage range
o Overload Protection (OLP) with auto-
recovery
o Over Temperature Protection (OTP) with
latch shut down
o VDD Over voltage Protection(OVP) with
latch shut down
o Adjustable OVP through external Zener
APPLICATIONS
Offline AC/DC flyback converter for
Battery Charger
Power Adapter
Set-Top Box Power Supplies
Open-frame SMPS
TYPICAL APPLICATION
©On-Bright Electronics
Confidential
-1-
Preliminary Datasheet
OB_DOC_DS_227305
Free Datasheet http://www.datasheet4u.com/

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OB2273
High Performance Current Mode PWM Controller
GENERAL INFORMATION
Pin Configuration
The OB2273 is offered in SOT23-6 and DIP8
package, shown as below.
Ordering Information
Part Number
OB2273MP
Description
SOT23-6, Pb-free in T&R
OB2273AP
DIP8, Pb-free in Tube
Package Dissipation Rating
Package
RθJA(/W)
SOT23-6
200
DIP8
90
Absolute Maximum Ratings
Parameter
VDD DC Supply Voltage
VDD Zener Clamp
VoltageNote
VDD DC Clamp Current
FB Input Voltage
Sense Input Voltage
RT Input Voltage
Min/Max Operating
Junction Temperature TJ
Min/Max Storage
Temperature Tstg
Lead
Temperature
(Soldering, 10secs)
Value
30 V
VDD_Clamp+0.1V
10 mA
-0.3 to 7V
-0.3 to 7V
-0.3 to 7V
-40 to 150
-55 to 160
260
Note: VDD_Clamp has a nominal value of 32V.
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.
OB2273 X
X
Current Mode PWM Controller with
Frequency shuffling
Package Package Pb free
M:SOT23-6
A: DIP8
Blank:Normal
P:lead-free
©On-Bright Electronics
Confidential
-2-
Preliminary Datasheet
OB_DOC_DS_227305
Free Datasheet http://www.datasheet4u.com/

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Marking Information
73YWW
S
Y:Year Code
WW:Week Code(01-52)
S:Internal Code(Optional)
OB2273
High Performance Current Mode PWM Controller
TERMINAL ASSIGNMENTS
Pin Name
GND
FB
RT
CS
VDD
Gate
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.
Dual function pin. Either connected through a NTC resistor to ground for over
I temperature shutdown/latch control or connected through Zener to VDD for
adjustable over voltage protection
I Current sense input
P Power Supply
O Totem-pole gate driver output for power Mosfet
RECOMMENDED OPERATING CONDITION
Symbol
VDD
TA
Parameter
VDD Supply Voltage
Operating Ambient Temperature
Min/Max
12 to 25
-40 to 85
Unit
V
©On-Bright Electronics
Confidential
-3-
Preliminary Datasheet
OB_DOC_DS_227305
Free Datasheet http://www.datasheet4u.com/

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BLOCK DIAGRAM
OB2273
High Performance Current Mode PWM Controller
©On-Bright Electronics
Confidential
-4-
Preliminary Datasheet
OB_DOC_DS_227305
Free Datasheet http://www.datasheet4u.com/

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OB2273
High Performance Current Mode PWM Controller
ELECTRICAL CHARACTERISTICS
(TA = 25, VDD=18V, unless otherwise noted)
Symbol
Parameter
Test Conditions
Min Typ Max Unit
Supply Voltage (VDD)
Istartup
VDD Start up Current
VDD=UVLO(OFF)-
1V, measure leakage
current into VDD
5 20 uA
I_VDD_Operation Operation Current
VDD=18V,VFB=3V,
CS=0V,Cgate=1nF
1.8 2.5 mA
UVLO(ON)
VDD Under Voltage Lockout
Enter
89
10 V
UVLO(OFF)
VDD Under Voltage Lockout
Exit (Recovery)
14.3 15.3 16.3 V
Vpull-up
Pull-up PMOS active
13 V
Vdd_clamp
Ivdd=10mA
30 32 34 V
OVP(ON)
Over voltage
voltage
protection
CS=0V,FB=3V
Ramp up VDD until
26
gate clock is off
28
30 V
Vlatch_release Latch release voltage
5V
Feedback Input Section(FB Pin)
VFB_Open
VFB Open Loop Voltage
Avcs
PWM input gain Δ VFB/ Δ
VCS
3.9 4.2
2
V
V/V
Maximum duty Max duty cycle @
cycle
VDD=18V,VFB=3V,VCS=0V
75 80 85 %
Vref_green
The threshold enter green
mode
2V
Vref_burst_H
The threshold exit burst mode
1.275
V
Vref_burst_L
The threshold enter burst
mode
1.175
V
IFB_Short
FB pin short circuit current
Short FB pin to GND
and measure current
0.4
mA
VTH_PL
Power Limiting FB Threshold
Voltage
3.7 V
TD_PL
Power limiting Debounce
Time
80 88 96 mSec
ZFB_IN
Input Impedance
16 Kohm
Current Sense Input(CS Pin)
SST Soft start time
4 ms
T_blanking
Leading edge blanking time
220 ns
ZSENSE_IN
Input Impedance
From Over Current
40
Kohm
TD_OC
Over Current Detection and Occurs till the
Control Delay
Gatedrive output start
to turn off
120
nSec
VTH_OC
Internal Current Limiting
Threshold Voltage with zero
duty cycle
0.75 V
Vocp_clamping CS voltage clamper
0.9 V
Oscillator
FOSC
Normal Oscillation Frequency
VDD=18V,
CS=0V
FB=3V, 60
65
70 KHZ
f_OSC
Frequency jittering
+/-4 %
F_shuffling
Shuffling frequency
32 Hz
©On-Bright Electronics
Confidential
-5-
Preliminary Datasheet
OB_DOC_DS_227305
Free Datasheet http://www.datasheet4u.com/