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OB2273A
High Performance Current Mode PWM Controller
GENERAL DESCRIPTION
OB2273A 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 OB2273A.
OB2273A offers complete protection coverage
with auto-recovery including Cycle-by-Cycle
current limiting (OCP), over load protection (OLP),
VDD under voltage lockout (UVLO), 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.
OB2273A is offered in SOT23-6 package.
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 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
auto-recovery
o VDD Over voltage Protection(OVP) with
auto-recovery
o Adjustable OVP through external Zener
APPLICATIONS
Offline AC/DC flyback converter for
Battery Charger
Power Adaptor
Set-Top Box Power Supplies
Open-frame SMPS
TYPICAL APPLICATION
©On-Bright Electronics
Confidential
-1-
Datasheet
OB_DOC_DS_2273AA2

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OB2273A
High Performance Current Mode PWM Controller
GENERAL INFORMATION
Pin Configuration
The OB2273A is offered in SOT23-6 package,
shown as below.
Ordering Information
Part Number
OB2273AMP
Description
SOT23-6, Pb-free in T&R
Package Dissipation Rating
Package
RJA(/W)
SOT23-6
200
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
VOVP-1V
VDD_Clamp+0.1V
10 mA
-0.3 to 7V
-0.3 to 7V
-0.3 to 7V
-40 to 150
-55 to 150
260
Note: VDD_Clamp has a typical 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.
OB2273A X
X
Current Mode PWM Controller with
Frequency shuffling
Marking Information
Package
M:SOT23-6
Package Pb-free
P:Pb-free
73YWW S
. ZZZA
©On-Bright Electronics
Y:Year Code
WW:Week Code(01-52)
s: Internal code
ZZZ: Lot code
A: Character code
Confidential
-2-
Datasheet
OB_DOC_DS_2273AA2

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OB2273A
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
RECOCM:MOpEtiNonDalEInDteOrnaPl ECRodAeTING CONDITION
Symbol
VDD
TA
Parameter
VDD Supply Voltage
Operating Ambient Temperature
Min/Max
12 to 25
-20 to 85
Unit
V
BLOCK DIAGRAM
©On-Bright Electronics
Confidential
-3-
Datasheet
OB_DOC_DS_2273AA2