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OB2276A
High Performance Current Mode PWM Controller
GENERAL DESCRIPTION
OB2276A 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 OB2276A.
OB2276A offers complete protection coverage
with auto-recovery including Cycle-by-Cycle
current limiting (OCP), over load protection (OLP),
Brownout protection, VDD over voltage protection
(OVP), over temperature protection (OTP), output
over voltage protection and VDD under voltage
lockout (UVLO). Excellent EMI performance is
achieved with On-Bright proprietary frequency
shuffling technique.
The tone energy at below 22KHZ is minimized in
the design and audio noise is eliminated during
operation.
OB2276A is offered in SOP8 package.
TYPICAL APPLICATION
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 Brownout Protection with auto-recovery
o VDD OVP with auto-recovery
o Over Temperature Protection with auto-
recovery
o Output Over Voltage Protection with auto-
recovery
APPLICATIONS
Offline AC/DC flyback converter for
Battery Charger
Power Adapter
Set-Top Box Power Supplies
Open-frame SMPS
©On-Bright Electronics
Confidential
-1-
Preliminary Datasheet
OB_DOC_DS_2276A00

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OB2276A
High Performance Current Mode PWM Controller
GENERAL INFORMATION
Pin Configuration
The OB2276A is offered in SOP8 package, shown
as below.
VCC
1
8 Demag
GND
2
7 FB
GATE
3
CS 4
6 RT
5 BO
Ordering Information
Part Number
OB2276ACP
Description
SOP8, Pb-free in Tube
OB2276ACPA
SOP8, Pb-free in T&R
Package Dissipation Rating
Package
RJA(/W)
SOP8
150
Absolute Maximum Ratings
Parameter
VDD DC Supply Voltage
Value
VOVP-1V
VDD Zener Clamp
VoltageNote
VDD_Clamp+0.1V
VDD DC Clamp Current 10 mA
FB Input Voltage
-0.3 to 7V
Sense Input Voltage
-0.3 to 7V
BO Input Voltage
-0.3 to 7V
RT Input Voltage
-0.3 to 7V
Min/Max Operating
Junction Temperature TJ
-40 to 150
Min/Max Storage
Temperature Tstg
-55 to 150
Lead Temperature
(Soldering, 10secs)
260
Note: VDD_Clamp has a nominal value of 34V.
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.
OB2276A X X X
Current Mode PWM Controller with
auto-recovery
Package
C:SOP8
Package Pb-free
P:Pb-free
Packing
Blank:Tube
A: Tape/Reel
©On-Bright Electronics
Confidential
2
Preliminary Datasheet
OB_DOC_DS_2276A00

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Marking Information
OB2276A
High Performance Current Mode PWM Controller
TERMINAL ASSIGNMENTS
Pin Name
VCC
GND
Gate
CS
BO
RT
FB
Demag
I/O Description
P Power Supply
P Ground
O Totem-pole gate driver output for power Mosfet
I Current sense input
I
Line voltage detection pin. Depends on voltage at this pin, Brownout is triggered or
not.
I Connected through a NTC resistor to ground for over temperature control.
I
Feedback input pin. The PWM duty cycle is determined by voltage level into this pin
and the current-sense signal at Pin 4.
I
Output detection pin through winding of transformer for output over voltage
protection
RECOMMENDED OPERATING CONDITION
Symbol
VDD
TA
Parameter
VDD Supply Voltage
Operating Ambient Temperature
Min/Max
12 to 27
-20 to 85
Unit
V
©On-Bright Electronics
Confidential
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Preliminary Datasheet
OB_DOC_DS_2276A00

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BLOCK DIAGRAM
OB2276A
High Performance Current Mode PWM Controller
©On-Bright Electronics
Confidential
-4-
Preliminary Datasheet
OB_DOC_DS_2276A00

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OB2276A
High Performance Current Mode PWM Controller
ELECTRICAL CHARACTERISTICS
(TA = 25, VDD=18V, unless otherwise noted)
Symbol
Parameter
Supply Voltage (VDD)
Istartup
VDD Start up Current
I_VDD_Operation Operation Current
UVLO(ON)
UVLO(OFF)
Vpull-up
VDD Under Voltage Lockout
Enter
VDD Under Voltage Lockout
Exit (Recovery)
Pull-up PMOS active
OVP(ON)
Over Voltage Protection
Voltage
Vdd_clamp
Feedback Input Section(FB Pin)
VFB_Open
VFB Open Loop Voltage
Avcs
PWM input gain Δ VFB/ Δ
VCS
Maximum duty Max duty cycle @
cycle
VDD=18V,VFB=3V,VCS=0V
Vref_green
Vref_burst_H
Vref_burst_L
The threshold enter green
mode
The threshold exit burst mode
The threshold enter burst
mode
IFB_Short
FB pin short circuit current
VTH_PL
Power Limiting FB Threshold
Voltage
TD_PL
Power limiting Debounce
Time
ZFB_IN
Input Impedance
Current Sense Input(CS Pin)
SST Soft start time
T_blanking
Leading edge blanking time
ZSENSE_IN
Input Impedance
TD_OC
Over Current Detection and
Control Delay
VTH_OC
Vocp_clamping
Oscillator
FOSC
f_OSC
F_shuffling
f_Temp
Internal Current Limiting
Threshold Voltage with zero
duty cycle
CS voltage clamper
Normal Oscillation Frequency
Frequency jittering
Shuffling frequency
Frequency
Temperature
Stability
Test Conditions
VDD=UVLO(OFF)-
1V, measure leakage
current into VDD
VDD=18V,VFB=3V,
CS=0V,Cgate=1nF
CS=0V,FB=3V
Ramp up VDD until
gate clock is off
Ivdd=10mA
Short FB pin to GND
and measure current
From Over Current
Occurs till the Gate
driver output starts to
turn off
VDD=18V, FB=3V,
CS=0V
Min
8
19
28.5
32
3.9
75
80
0.65
62
Typ
3
1.8
9
20
13
30
34
4.2
2
80
1.65
1.25
1.15
0.2
3.7
88
16
4
220
40
100
0.7
0.9
65
+/-4
50
1
Max Unit
20 uA
2.5 mA
10 V
21 V
V
31.5 V
36 V
V
V/V
85 %
V
V
V
mA
V
96 ms
k
ms
ns
k
ns
0.75 V
V
68 kHz
%
Hz
%
©On-Bright Electronics
Confidential
-5-
Preliminary Datasheet
OB_DOC_DS_2276A00