GENERAL DESCRIPTION
Briard combines a dedicated current mode PWM controller. It is optimized for high performance, low standby power (< 100mW), and cost effective off-line flyback converter applications in 40W~60W range.
Briard offers complete protection coverage with automatic lf-recovery feature including Cycle-by-Cycle current limiting (OCP), CS short protection, CS floating protection, over load protection (OLP), and VDD under voltage lockout (UVLO) and latch feature including over temperature protection (OTP), over voltage(fixed or adjustable) protection (OVP). 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 noi is eliminated during operation.
Briard is offered in SOT23-6 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
面试案例
■ Auxiliary Power Supply for PC and Server ■ Open-frame SMPS
FEATURES
■
Power on Soft Start Reducing MOSFET Vds Stress
■ Frequency shuffling for EMI
■ Extended Burst Mode Control For Improved
青岛itEfficiency and Minimum Standby Power Design
■ Audio Noi Free Operation
■ Fixed 65KHZ Switching Frequency
■ Internal Synchronized Slope Compensation ■ Leading Edge Blanking on Current Sen
Input
■ Good Protection Coverage With Auto Self-Recovery
rocketso VDD Under Voltage Lockout with Hysteresis
(UVLO)
o Over Temperature Protection (OTP) with
latch
o Cycle-by-cycle over current threshold
tting for constant output power limiting over universal input voltage range
o Overload Protection (OLP) with auto-recovery
o Over voltage Protection(OVP) with latch o Adjustable OVP through external Zener o CS floating protection with auto-recovery o CS short protection with auto-recovery
TYPICAL APPLICATION
Product Specification
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GENERAL INFORMATION
Pin Configuration
The OB2273 is offered in SOT23-6 package,
shown as below.
Ordering Information Part Number Description OB2273MP SOT23-6, Pb-free in T&R
Package Dissipation Rating Package R θJA(℃/W)
SOT23-6 200
Absolute Maximum Ratings Parameter Value VDD DC Supply Voltage 40 V VDD Zener Clamp
Voltage Note
VDD_Clamp+0.1V
VDD DC Clamp Current 10 mA FB Input Voltage -0.3 to 7V Sen Input Voltage -0.3 to 7V RT Input Voltage -0.3 to 7V Min/Max Operating
Junction Temperature TJ -20 to 150 oC
Min/Max Storage
Temperature Tstg
-55 to 160 oC
Note:VDD_Clamp has a nominal value of 32V.
Stress beyond tho listed under “absolute maximum ratings” may cau permanent damage to the device. The are stress ratings only, functional operation of the device at the or any other conditions beyond tho indicated under “recommended operating conditions” is not implied. Exposure to absolute maximum-rated conditions for extended periods may affect device reliability.
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Marking Information
TERMINAL ASSIGNMENTS
For SOT23-6
Pin Name I/O Description GND P Ground
FB I
Feedback input pin. The PWM duty cycle is determined by voltage level into this pin
and the current-n signal at Pin 3.
RT I Dual function pin. Either connected through a NTC resistor to ground for over
temperature shutdown/latch control or connected through Zener to VDD for
adjustable over voltage protection
CS I Current n input VDD P Power
Supply Gate O Totem-pole gate driver output for power Mosfet
RECOMMENDED OPERATING CONDITION
Symbol Parameter
Min/Max Unit VDD VDD Supply Voltage
10 to 30 V T A
Operating Ambient Temperature
-20 to 85
℃
C: Optional Internal Code
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ELECTRICAL CHARACTERISTICS
(T A = 25℃, VDD=16V, unless otherwi 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
V FB =3V 1.8 2.5 mA UVLO(ON)
VDD Under Voltage Lockout
Enter
6 7 8 V
UVLO(OFF)
VDD Under Voltage Lockout
Exit (Recovery)
12.5 13.5 14.5V
Vpull-up Pull-up PMOS active 13 V Vdd_clamp
Ivdd =10mA 30 32 34 V OVP(ON) Over voltage protection
voltage
CS=0V,FB=3V
Ramp up VDD until gate clock is off
parfun
24 26 28 V
Vlatch_relea Latch relea voltage 5 V Feedback Input Section(FB Pin)
V FB_Open V FB Open Loop Voltage 3.9 4.2 V
Avcs PWM input gain ΔVFB/Δ
VCS
2 V/V
Maximum duty cycle Max duty cycle @
VDD=14V,VFB=3V,VCS=0V
75 80 85 %
Vref_green The threshold enter green
mode
1.4 V
Vref_burst_H The threshold exit burst
mode
不用谢用英语怎么说
0.675 V
Vref_burst_L The threshold enter burst
mode
0.575 V
I FB _Short FB pin short circuit current Short FB pin to GND
and measure current
0.3 mA
V TH _PL Power Limiting FB
Threshold Voltage
3.7 V
T D _PL Power limiting Debounce
Time
80 88 96 mSec
Z FB _IN Input Impedance 4 Kohm Current Sen Input(Sen Pin) Soft start time 4 ms T_blanking Leading edge blanking time 220 ns Z SENSE _IN Input Impedance 40 Kohm
T D _OC Over Current Detection and
Control Delay
From Over Current
Occurs till the Gatedrive output start to turn off
120
nSec V TH _OC Internal Current Limiting Threshold Voltage FB=3.3V
0.75 V
Vocp_clamper CS voltage clamper 0.9 V Oscillator
F OSC Normal Oscillation Frequency VDD =14V, FB =
3V,
CS=0V
60 65 70 KHZ
△f_OSC Frequency jittering +/-4 % F_shuffling Shuffling frequency 32 Hzaddle
△f_Temp Frequency Temperature
Stability
1 %
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