MC7731N6 CYSTEKEC | Alldatasheet

Document overview

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Technical content

Features

  • Frequency jitter function to improve EMI performance of power supply
  • No-audible-noise green mode Control
  • External Programmable PWM Switching Frequency
  • Internal Slope Compensation
  • Low VDD Startup Current and Low Operating Current
  • Leading Edge Blanking
  • UVLO
  • Gate Max Output Voltage Clamp at 18V
  • Overload Protection (OLP).
  • Line Compensation Over Current Protection (OCP)

Applications

Offline AC/DC flyback converter for

  • Battery Charger
  • Power Adaptor
  • Set-Top Box Power Supplies
  • Open-frame SMPS
  • PC 5V Standby Power

CYStech Electronics Corp. Spec. No. : C494N6 Issued Date : 2012.04.02 Revised Date : Page No. : 2/10 MC7731N6 CYStek Product Specification

Ordering Information

(Pb-free lead plating) 3000 pcs / tape & reel Typical Application Circuit Pin Configuration

CYStech Electronics Corp. Spec. No. : C494N6 Issued Date : 2012.04.02 Revised Date : Page No. : 3/10 MC7731N6 CYStek Product Specification Pin Assignment Pin Name Pin Number Pin Function GND 1 Ground FB 2 Feedback input pin. The PWM duty cycle is determined by voltage level into this pin and the current-sense signal at Pin 6. RI 3 Internal Oscillator frequency setting pin. A resistor connected between RI and GND sets the PWM frequency. SENSE 4 Current sense input pin. Connected to MOSFET current sensing resistor node. VDD 5 Chip DC power supply pin. GATE 6 Totem-pole gate drive output for the power MOSFET. Function Block Diagram Absolute Maximum Ratings Parameter Value Unit VDD to GND -0.3 to +30 V VDD clamped current 10 mA VDD clamped voltage 29 V VFB, VSENSE and VRI to GND -0.3~+7 V Maximum Junction Temperature (Tj MAX) -20° to +150 °C Storage Temperature Range -55 ~ +150 °C Note：Stresses beyond those listed under “Absolute Maximum Ratings" may cause permanent damage to the device.

CYStech Electronics Corp. Spec. No. : C494N6 Issued Date : 2012.04.02 Revised Date : Page No. : 4/10 MC7731N6 CYStek Product Specification Recommended Operating Conditions

Electrical Characteristics

(TA = 25°C, RI=100kΩ, VDD=16V if not otherwise noted) Parameter Symbol Test Conditions Min Typ Max Units SUPPLY SECTION Chip start up current via VDD pin I_set Vdd=12V, measure current into VDD pin 5 20 uA Operation current I_op VDD=16V,VFB=3V 1.4 mA VDD Off(Turn-off threshold) UVLO_L 8 9 10 V VDD on(Turn-on threshold) UVLO_H 13 14 15 V VZ(VDD clamp voltage) VDD_CLP Iz(Idd)=10mA 34 V FEEDBACK SECTION PWM input gain A_PWM ΔVFB/ΔVCS 2 V/V VFB open loop voltage VFB_O 5.3 V FB pin short circuit current VFB_S Short FB pin to gnd and measure current 0.8 mA Zero duty cycle FB threshold VFB_th_L 0.75 V Power limiting FB threshold VFB_th_P 3.7 V Power limiting delay time T_PL_D 35 ms Input impedance R_FB 6 KΩ Maxim duty cycle D_MAX VDD=18V, FB=3V,CS=0 80 % OSCILLATOR Normal oscillation frequency FOSC 60 65 70 kHz Frequency temperature stability Δf_Temp TA = -20°C to +100°C 5 % Frequency supply stability Δf_Sup VDD =12-25V 5 % Operating RI range RI_range 50 100 150 KΩ RI open load voltage RI_open 2 V Burst mode base frequency FOSC-BM 22 KΩ Frequency modulate range (jitter) Δf_OSC -3 3 % Jitter frequency f_jitter 32 Hz CURRENT SENSE SECTION Leading edge blanking time T_blank 300 nS Sense pin input impedance R_sense 40 kΩ Over current threshold voltage at sense pin VTH_OC FB=3.3V 0.7 0.75 0.8 V Over current protect delay T_OC_D CS>VTH_OC, FB=3.3V 75 nS GATE OUTPUT Output low level VOL Io=20mA 0.8 V Output high level VOH Io=20mA 10V V

CYStech Electronics Corp. Spec. No. : C494N6 Issued Date : 2012.04.02 Revised Date : Page No. : 5/10 MC7731N6 CYStek Product Specification Output voltage clamped level VO_clamp 18 V Output rising time Tr Cl=1nf 220 nS Output falling time Tf Cl=1nf 70 ns OPERATION DESCRIPTION Over-view description The MC7731N6 includes all necessary function to build an easy and cost effective solution for low power supplies to meet the international power conservation requirements. Start-up current Startup current of MC7731N6 is designed to be very lo w so that VDD could be charged up above UVLO (exit) threshold level and device starts up quickly. Also a large value startup resistor can be used to minimize the power loss. Green Mode Operation （Patent） At light load or no load condition, the switch lo ss become the major loss of the power supply, to reduce the power wasted in light and no load condition, based on a special designed voltage controlled oscillator, green mode operation of the power supply can be achieved by using MC7731N6. The controller will judge the load condition based on the voltage of FB pin. In light load the FB volt age will decrease, when VFB is lower than a set threshold voltage, a FB depending time (TR2) will be generated by the oscillator and decrease the operating frequency of the power supply, the minimum frequency is set about 22kHZ. The function block and the working waveform can be depicted as below:

CYStech Electronics Corp. Spec. No. : C494N6 Issued Date : 2012.04.02 Revised Date : Page No. : 6/10 MC7731N6 CYStek Product Specification When VFB decreases further, the power supply will enter into burst mode operation to decrease the power consumed at no load condition. Besides there is no audible noise in any load condition. Oscillator Operation A resistor from RI pin to ground will generate a constant current source for MC7731N6. This current is used to charge/discharge an internal capacitor and hence the internal clock and switching frequency are determined. Increase the resistance will decrease the current source and reduce the switching frequency. The relation between Ri and switching frequency is: Built-in Slope Compensation The sensed voltage across the sense resistor is used for pwm control, and pulse by pulse current limit. Built-in slope compensation circuit adds a voltage ramp onto the current sense input voltage. This greatly improves the close loop stability and prevents the sub-harmonic oscillation of peak current mode pwm control scheme. Leading Edge Blanking Each time when the power MOSFET is switched on, a turn-on spike will inevitably occur on the sense-resistor. To avoid premature termination of the switching pulse, a 270 nsec leading-edge blanking time is built in. Conventional RC filtering can theref ore be omitted. During this blanking period, the current-limit comparator is disabled and it cannot switch off the gate driver. Gate Driver The output stage of MC7731N6 is a fa st totem pole gate driver. Cross conduction has b een avoided to minimize heat dissipation, increases efficiency and enhances reliability. The output driver is clamped by an internal 18V Zener diode in order to protect powe r MOSFET transistors against undesirable gate over voltage. A soft driving waveform is implemented to minimize EMI. Frequency Jitter The frequency jitter function is integrated in the controller, the jitter is modulated by a periodic signal, the modulate signal frequency is much smaller than the oscillator frequency, By this way，the EMI noise has a wider spectrum with lower amplitudes.

CYStech Electronics Corp. Spec. No. : C494N6 Issued Date : 2012.04.02 Revised Date : Page No. : 7/10 MC7731N6 CYStek Product Specification Protect Functions To increase the reliability of power supply system, many protection functions are integrated in this controller, including Cycle-by-Cycle current limiting (OCP), Over Load Protection (OLP) and over voltage clamp, Under Voltage Lockout on VDD (UVLO). At overload condition when FB input voltage exceeds power limit threshold value for more than TD_PL (power limit debounce time), the controller 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.

CYStech Electronics Corp. Spec. No. : C494N6 Issued Date : 2012.04.02 Revised Date : Page No. : 8/10 MC7731N6 CYStek Product Specification Reel Dimension Carrier Tape Dimension

CYStech Electronics Corp. Spec. No. : C494N6 Issued Date : 2012.04.02 Revised Date : Page No. : 9/10 MC7731N6 CYStek Product Specification Recommended wave soldering condition Product Peak Temperature Soldering Time Pb-free devices 260 +0/-5 °C 5 +1/-1 seconds Recommended temperature profile for IR reflow Profile feature Sn-Pb eutectic Assembly Pb-free Assembly Average ramp-up rate (Tsmax to Tp) 3°C/second max. 3°C/second max. Preheat −Temperature Min(TS min) −Temperature Max(TS max) −Time(ts min to ts max) 100°C 150°C 60-120 seconds 150°C 200°C 60-180 seconds Time maintained above: −Temperature (TL) − Time (tL) 183°C 60-150 seconds 217°C 60-150 seconds Peak Temperature(TP) 240 +0/-5 °C 260 +0/-5 °C Time within 5°C of actual peak temperature(tp) 10-30 seconds 20-40 seconds Ramp down rate 6°C/second max. 6°C/second max. Time 25 °C to peak temperature 6 minutes max. 8 minutes max. Note : All temperatures refer to topside of the package, measured on the package body surface.

CYStech Electronics Corp. Spec. No. : C494N6 Issued Date : 2012.04.02 Revised Date : Page No. : 10/10 MC7731N6 CYStek Product Specification SOT-23-6L Dimension J 12 3 456 A B C D d1 d2 E F G K I LH Marking: 6-Lead SOT-23-6L Plastic Surface Mounted Package CYStek Package Code: N6 Style: Pin 1. GND Pin 2. FB Pin 3. DEM Pin 4. SENSE Pin 5. VDD Pin 6. GATE 63ABC Device Name Date Code D 0.0748 REF 1.90 REF I 0.0047 REF 0.12 REF d1 0.0374 REF 0.95 REF J 0.0146 REF 0.37 REF d2 0.0374 REF 0.95 REF K 0.0236 REF 0.60 REF E 0.0118 0.0217 0.30 0.55 L 0° 10° 0° 10° Notes : 1.Controlling dimension : millimeters. 2.Maximum lead thickness includes lead finish thickness, and minimum lead thickness is the minimum thickness of base material. 3.If there is any question with packing specification or packing method, please contact your local CYStek sales office. Material :

  • Mold Compound : Epoxy resin family, flammability solid burning class:UL94V-0 Important Notice:
  • All rights are reserved. Reproduction in whole or in part is prohibited without the prior written approval of CYStek.
  • CYStek reserves the right to make changes to its products without notice.
  • CYStek semiconductor products are not warranted to be suitable for use in Life-Support Applications, or systems.
  • CYStek assumes no liability for any consequence of customer product design, infringement of patents, or application assistance.