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OB2263 Current Mode PWM ControllerFrequency Shuffling
GENERAL DESCRIPTION
OB2263 is a highly integrated current mode PWM control IC optimized for high performance, low standby power and cost effective offline flyback converter applications in sub 30W range. PWM switching frequency at normal operation is externally programmable and 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 design with OB2263. A large value resistor could thus be used in the startup circuit to minimize the standby power. The internal slope compensation improves system large signal stability and reduces the possible subharmonic oscillation at high PWM duty cycle output. Leading-edge blanking on current sense(CS) input removes the signal glitch due to snubber circuit diode reverse recovery and thus greatly reduces the external component count and system cost in the design. OB2263 offers complete protection coverage with automatic self-recovery feature including Cycle-byCycle current limiting (OCP), over load protection (OLP), VDD over voltage clamp and under voltage lockout (UVLO). The Gate-drive output is clamped to maximum 18V to protect the power MOSFET. Excellent EMI performance is achieved with OnBright proprietary frequency shuffling technique together with soft switching control at the totem pole gate drive output. Tone energy at below 20KHZ is minimized in the design and audio noise is eliminated during operation. OB2263 is offered in SOT23-6, SOP-8 and DIP-8 packages.
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TYPICAL APPLICATION
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On-Bright Proprietary Frequency Shuffling Technology for Improved EMI Performance. Extended Burst Mode Control For Improved Efficiency and Minimum Standby Power Design Audio Noise Free Operation External Programmable PWM Switching Frequency Internal Synchronized Slope Compensation Low VDD Startup Current and Low Operating Current (1.4mA) Leading Edge Blanking on Current Sense Input Good Protection Coverage With Auto SelfRecovery o VDD Over Voltage Clamp and Under Voltage Lockout with Hysteresis (UVLO) o Gate Output Maximum Voltage Clamp (18V) o On-Bright Proprietary Line Input Compensated Cycle-by-Cycle Over-current Threshold Setting For Constant Output Power Limiting Over Universal Input Voltage Range. o Overload Protection (OLP)
APPLICATIONS
Offline AC/DC flyback converter for Battery Charger Power Adaptor Set-Top Box Power Supplies Open-frame SMPS
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FEATURES
OB2263 Current Mode PWM ControllerFrequency Shuffling
GENERAL INFORMATION
Pin Configuration The OB2263 is offered in SOT23-6, DIP8 and SOP8 packages, shown as below. Part Number OB2263MP OB2263AP OB2263CP Description SOT23-6, Pb-free DIP8, Pb-free SOP8, Pb-free
200
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Ordering Information
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Absolute Maximum Ratings Parameter Value VDD DC Supply Voltage 30 V VDD Clamp Voltage 34V VDD DC Clamp Current 10 mA VFB Input Voltage -0.3 to 7V VSENSE Input Voltage to Sense -0.3 to 7V Pin VRI Input Voltage to RI Pin -0.3 to 7V Min/Max Operating Junction -20 to 150 oC Temperature TJ Min/Max Storage Temperature -55 to 160 oC Tstg 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.
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DIP8 SOP8 SOT23-6
90 150
(°C/W)
Package Dissipation Rating RJA Package
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OB2263 Current Mode PWM ControllerFrequency Shuffling
Marking Information
TERMINAL ASSIGNMENTS
Pin Name GND FB RI SENSE VDD GATE I/O P I I I P O
VDD RI TA
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Symbol
Parameter
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RECOMMENDED OPERATING CONDITION
Min Max 10 to 30 100 -20 to 85 Unit V Kohm o C
VDD Supply Voltage RI Resistor Value Operating Ambient Temperature
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Description Ground Feedback input pin. The PWM duty cycle is determined by voltage level into this pin and SENSE pin input. Internal Oscillator frequency setting pin. A resistor connected between RI and GND sets the PWM frequency. Current sense input pin. Connected to MOSFET current sensing resistor node. Chip DC power supply pin. Totem-pole gate drive output for the power MOSFET.
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OB2263 Current Mode PWM ControllerFrequency Shuffling
BLOCK DIAGRAM
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OB2263 Current Mode PWM ControllerFrequency Shuffling
ELECTRICAL CHARACTERISTICS
(TA = 25OC if not otherwise noted) Symbol Parameter Supply Voltage (VDD) I_VDD_Startup VDD Start up Current I_VDD_Ops UVLO(ON) Operation Current Test Conditions VDD =12.5V, RI=100K Measure Leakage current into VDD VDD=16V, RI=100Kohm, VFB=3V 7.8 13 IVDD = 10 mA VFB /Vcs Short FB pin to GND and measure current VDD = 16V, RI=100Kohm Min Typ 3 1.4 8.8 14 34 9.8 Max 20 Unit
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VDD Under Voltage Lockout Enter UVLO(OFF) VDD Under Voltage Lockout Exit (Recovery) VDD_Clamp VDD Zener Clamp Voltage Feedback Input Section(FB Pin) AVCS PWM Input Gain VFB_Open VFB Open Loop Voltage IFB_Short FB pin short circuit current VTH_0D Zero Duty Cycle FB Threshold Voltage VTH_PL Power Limiting FB Threshold Voltage TD_PL Power limiting Debounce Time ZFB_IN Input Impedance DC_MAX Maximum Duty Cycle
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2.0 4.8 1.2 0.75
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3.7 35 6 75
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Current Sense Input(Sense Pin) T_blanking Leading edge blanking time ZSENSE_IN Input Impedance TD_OC Over Current Detection and Control Delay VTH_OC Over Current Threshold Voltage at zero Duty Cycle Oscillator FOSC Normal Oscillation Frequency
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VDD=18V, RI=100Kohm, FB=3V, CS=0 RI = 100 Kohm VDD = 16V, CS>VTH_OC, FB=3.3V
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300 40 75 0.70 0.75 0.80
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FB=3.3V, RI=100 Kohm
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RI = 100 Kohm VDD = 16V, RI=100Kohm, TA -20oC to 100 oC VDD = 12-25V, RI=100Kohm
60
65 5 5
f_Temp f_VDD RI_range V_RI_open
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Frequency Temperature Stability Frequency Voltage Stability Operating RI Range RI open load voltage
50
100 2
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15 V V V/V V mA V V mSec Kohm % ns Kohm nSec V 70 KHZ % % 150 Kohm V
V
mA
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uA
OB2263 Current Mode PWM ControllerFrequency Shuffling
Fosc_BM Burst Mode Base Frequency VDD = 16V, RI = 100Kohm VDD = 16V, Io = -20 mA VDD = 16V, Io = 20 mA VDD = 16V, CL = 1nf VDD = 16V, CL = 1nf RI=100K RI=100K -3 64 10 18 220 70 3 22 0.8 KHZ V V V nSec nSec
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% HZ
Gate Drive Output VOL Output Low Level VOH Output High Level V_Clamp Output Clamp Voltage Level T_r Output Rising Time T_f Output Falling Time Frequency Shuffling Frequency f_OSC Modulation range /Base frequency f_shuffling Shuffling Frequency
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OB2263 Current Mode PWM ControllerFrequency Shuffling
CHARACTERIZATION PLOTS
VDD = 16V, RI = 100 Kohm, TA = 25oC condition applies if not otherwise noted.
VDD Startup Current vs. Voltage Ivdd_startup(uA ) 20
I_vdd_startup (uA)
5.0 4.6 4.2 3.8 3.4 3.0 -20
I_VDD_startup vs. Temp
10 5 0 0 2 4 6 8 10 12 14 16 VDD(V)
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40
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70 100 130
15
VDD UVLO and Ops Current 2 I(VDD) (mA) 1.6 1.2 0.8 0.4 0 0 5 10 15 VDD (V)
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VDD Operation Current vs. Load(pF) 50KHz 65KHz 100KHz
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I(V D D ) (m A )
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5 4 3 2 1 0
20
25
30
0
500
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Temp(C)
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UVLO(ON) vs Temp
14.5 14.4 14.3 14.2 14.1 14.0
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Gate Load (pF)
1000
1500
UVLO(OFF) vs Temp
UVLO(OFF) (V)
UVLO(ON) (V)
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8.8 8.6 8.4 8.2 8.0
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9.0
-20
10
40
70
100
130
-20
10
40
70
100
Temp(C)
Temp(C)
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130
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OB2263 Current Mode PWM ControllerFrequency Shuffling
140 Fosc(K H z) 90 65 40 50 70 90 110 RI(Kohm) 130 150
Fosc (KHz)
66.5 66 65.5 65 64.5 64 63.5 -20 5 30
115
V th_O C (V )
1.2 1.1 1 0.9 0.8 0.7 0
10
20
30 40 50 Duty_cycle(%)
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Vth_OC(V) vs Duty_cycle(%)
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105
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Fosc(KHz) vs. RI(Kohm)
Fosc vs. Temp
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OB2263 Current Mode PWM ControllerFrequency Shuffling
OPERATION DESCRIPTION
The OB2263 is a highly integrated PWM controller IC optimized for offline flyback converter applications in sub 30W power range. The extended burst mode control greatly reduces the standby power consumption and helps the design easily meet the international power conservation requirements. ˇ Startup Current and Start up Control Startup current of OB2263 is designed to be very low so that VDD could be charged up above UVLO threshold level and device starts up quickly. A large value startup resistor can therefore be used to minimize the power loss yet provides reliable startup in application. For AC/DC adaptor with universal input range design, a 2 M, 1/8 W startup resistor could be used together with a VDD capacitor to provide a fast startup and low power dissipation solution. ˇ Operating Current The Operating current of OB2263 is low at 1.4mA. Good efficiency is achieved with OB2263 low operating current together with extended burst mode control features. minimize the switching loss and reduces the standby power consumption to the greatest extend. The frequency control also eliminates the audio noise at any loading conditions. ˇ Oscillator Operation A resistor connected between RI and GND sets the constant current source to charge/discharge the internal cap and thus the PWM oscillator frequency is determined. The relationship between RI and switching frequency follows the below equation within the specified RI in Kohm range at nominal loading operational condition.
FOSC =
ˇ Extended Burst Mode Operation At zero load or light load condition, majority of the power dissipation in a switching mode power supply is from switching loss on the MOSFET transistor, the core loss of the transformer and the loss on the snubber circuit. The magnitude of power loss is in proportion to the number of switching events within a fixed period of time. Reducing switching events leads to the reduction on the power loss and thus conserves the energy. OB2263 self adjusts the switching mode according to the loading condition. At from no load to light/medium load condition, the FB input drops below burst mode threshold level. Device enters Burst Mode control. The Gate drive output switches only when VDD voltage drops below a preset level and FB input is active to output an on state. Otherwise the gate drive remains at off state to
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ˇ Frequency shuffling for EMI improvement The frequency Shuffling/jittering (switching frequency modulation) is implemented in OB2263. The oscillation frequency is modulated with a random source so that the tone energy is spread out. The spread spectrum minimizes the conduction band EMI and therefore reduces system design challenge.
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ˇ Current Sensing and Leading Edge Blanking Cycle-by-Cycle current limiting is offered in OB2263 current mode PWM control. The switch current is detected by a sense resistor into the sense pin. An internal leading edge blanking circuit chops off the sense voltage spike at initial MOSFET on state due to Snubber diode reverse recovery so that the external RC filtering on sense input is no longer required. The current limit comparator is disabled and thus cannot turn off the external MOSFET during the blanking period. PWM duty cycle is determined by the current sense input voltage and the FB input voltage. ˇ Internal Synchronized Slope Compensation Built-in slope compensation circuit adds voltage ramp onto the current sense input voltage for PWM generation. This greatly improves the close loop stability at CCM and prevents the sub-harmonic oscillation and thus reduces the output ripple voltage. ˇ Gate Drive OB2263 Gate is connected to an external MOSFET gate for power switch control. Too weak the gate drive strength results in higher conduction and switch loss of MOSFET while too strong gate drive output compromises the EMI. A good tradeoff is achieved through the built-in totem pole gate design with right output strength and dead time control. The low idle loss and good EMI system design is easier to achieve with this dedicated control scheme. An internal 18V clamp is added for MOSFET gate protection at higher than expected VDD input.
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6500 ( Khz ) RI ( Kohm)
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OB2263 Current Mode PWM ControllerFrequency Shuffling
ˇ Protection Controls Good power supply system reliability is achieved with its rich protection features including Cycle-byCycle current limiting (OCP), Over Load Protection (OLP) and over voltage clamp, Under Voltage Lockout on VDD (UVLO). With On-Bright Proprietary technology, the OCP threshold tracks PWM Duty cycles and is line voltage compensated to achieve constant output power limit over the universal input voltage range with recommended reference design. At overload condition when FB input voltage exceeds power limit threshold value for more than TD_PL, control circuit reacts to shut down the output power MOSFET. Device restarts when VDD voltage drops below UVLO limit. VDD is supplied by transformer auxiliary winding output. It is clamped when VDD is higher than threshold value. The power MOSFET is shut down when VDD drops below UVLO limit and device enters power on start-up sequence thereafter.
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OB2263 Current Mode PWM ControllerFrequency Shuffling
PACKAGE MECHANICAL DATA
SOT23-6
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OB2263 Current Mode PWM ControllerFrequency Shuffling
8-Pin Plastic DIP
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OB2263 Current Mode PWM ControllerFrequency Shuffling
8-Pin Plastic SOP
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OB2263 Current Mode PWM ControllerFrequency Shuffling
IMPORTANT NOTICE
RIGHT TO MAKE CHANGES On-Bright Electronics Corp. reserves the right to make corrections, modifications, enhancements, improvements and other changes to its products and services at any time and to discontinue any product or service without notice. Customers should obtain the latest relevant information before placing orders and should verify that such information is current and complete. WARRANTY INFORMATION On-Bright Electronics Corp. warrants performance of its hardware products to the specifications applicable at the time of sale in accordance with its standard warranty. Testing and other quality control techniques are used to the extent it deems necessary to support this warranty. Except where mandated by government requirements, testing of all parameters of each product is not necessarily performed. On-Bright Electronics Corp. assumes no liability for application assistance or customer product design. Customers are responsible for their products and applications using On-Bright's components, data sheet and application notes. To minimize the risks associated with customer products and applications, customers should provide adequate design and operating safeguards. LIFE SUPPORT On-Bright Electronics Corp.'s products are not designed to be used as components in devices intended to support or sustain human life. On-bright Electronics Corp. will not be held liable for any damages or claims resulting from the use of its products in medical applications. MILITARY On-Bright Electronics Corp.'s products are not designed for use in military applications. On-Bright Electronics Corp. will not be held liable for any damages or claims resulting from the use of its products in military applications.
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