STC494 Pulse Width Modulation Description The STC494 is a monolithic integrated circuit which includes all the necessary building blocks for the design of pulse width modulate(PWM) switching power supplies, including push-pull, bridge and series configuration. The device can operate at switching frequencies between 1KHz and 300KHz and output voltage up to 40V. The STC494 is specified over an operating temperature range of -40к to 85к . Features ΘUncommitted output transistors capable of 200mA source or sink! ΘInternal protection from double pulsing of out-puts with narrow pulse widths or with! supply voltages bellows specified limits! ΘEasily synchronized to other circuits! ΘDead time control comparator! ΘOutput control selects single-ended or push-pull operation! Ordering Information Type NO. Marking STC494 STC494 Outline Dimensions Package Code SOP-16 unit : mm PIN Connections 1. Non-INV Input 2. INV Input 3. Feed-Back 4. Dead-Time Control 5. CT 6. RT 7. GND 8. C1 9. E1 10. E2 11. C2 12. Vcc 13 Output Control 14. Ref Out 15. INV-Input 16. Non-INV Input 1 S STC494 Absolute Maximum Ratings Ta=25qC Characteristic Symbol Ratings Unit VCC 42 V supply voltage Voltage From Any Pin to Ground (except pin 8 and pin 11) Output Collector Voltage VIN VCC+0.3 V VC1, VC2 42 V Peak Collector Current IC1, IC2 250 mA Power Dissipation PD 1500 mW Operating Temperature Topr -40 ~ 85 qC Storage Temperature Tstg -65 ~ 150 qC Recommended Operating Condition Characteristic Symbol Min. Max. Unit VCC 7 40 V supply voltage Voltage on Any Pin Except Pin 8 and 11(Referenced to Ground) Output Voltage VIN -0.3 VCC+0.3 V VC1, VC2 -0.3 40 V Output Collector Current IC1, IC2 - 200 mA Timing Capacitor Ct 470 - PF Timing Capacitor Ct - 10 ༲ Timing Resistor Rt 1.8 500 ༮ fOSC 1 300 KHz Oscillator Frequency Electrical Characteristics Reference Section Characteristic Symbol Test Condition Reference Voltage Vref Iref = 1.0mA Line Regulation VLINE Load Regulation VLOAD Temperature Coefficient - Min. Typ. Max. Unit 4.75 5.00 5.25 V 7V < Vcc < 40V - 2 25 mV 1mA< IREF <10mA - 1 15 mV 0qC < Ta <70qC - 0.01 0.03 %/qC Min. Typ. Max. Unit Oscillator Section Characteristic Oscillator Frequency Oscillator Frequency Change Over Operating Temperature Range Symbol Test Condition fOSC Ct=0.01 ༲, Rt=12 ༮ - 10 - ༩ ȟ fSOC Ct=0.01 ༲, Rt=12 ༮ - - 2 % G 2 STC494 Dead Time Control Section Characteristic Input Bias Current (Pin4) Max. Duty cycle, Each Output Zero Duty Input Threshold Voltage Max Duty Symbol IIB(DT) DC(Max) VTH Test Condition Vcc = 15V, 0V < V4 < 5.25V Vcc = 15V, Pin4 = 0V, Output Control Pin = Vref - Min. Typ. Max. Unit - -2 -10 ༟ 43 - 45 % - 3 3.3 0 - - V Error Amplifier Section Characteristic Symbol Test Condition Min. Typ. Max. Unit Input Offset Voltage VIOS V3 = 2.5V - 2 10 mV Input Offset Current IIOS V3 = 2.5V - 25 250 nA Input Bias Current IIB V3 = 2.5V - 0.2 1 ༟ -0.3 - VCC V 60 74 - dB - 650 - ༩ Input Common Mode voltage Range Large Signal Open Loop Voltage Range Unity Gain Band width VICR 7V d VCC d 40V GVO 0.5V d V3 d 3.5V fC - PWM Comparator Section (Pin3) Characteristic Inhibit Threshold Voltage Output Source Current Output Sink Current Symbol VTHI Test Condition Min. Typ. Max. Unit Zero duty cycle - 4 4.5 V + 0.5V < V3 < 3.5V 2 - - mA - 0.5V< V3 < 3.5V -0.2 -0.6 - mA Io Io Output Section Characteristic Output Saturation Voltage Common-Emitter Emitter-Follower Symbol VCE(SAT) Test Condition Min. Typ. Max. VE= 15V, IC = 200mA - 1.1 1.3 VC =15V, IE = 200mA - 1.5 2.5 Unit V Collector off-state Current IC(off) VCC = VC = 40V, VE = 0 - 2 100 Emitter off-state Current IE(off) VCC = VC = 40V, VE = 0 - - -100 VOCL - - - 0.4 V VOCH - 2.4 - - V ICC - - 6 10 mA Output Control(Pin 13) Output Control Voltage Required for single-Ended or Parallel Output Operation Output Control Voltage Required for Push-pull operation Total Device Standby power Supply Current : These limits apply when the voltage measured at Pin 3 is with in the range specified. 3 STC494 Output AC Characteristic Characteristic Symbol Common Emitter Rise Time tr Emitter Follower Common Emitter Fall Time tf Emitter Follower Test Condition Min. Typ. Max. - - - 100 200 - 100 200 - 25 100 - 40 100 Unit ns Block Diagram · ΔΔ ͣ͢ Ζ Η͑ Φ Υ ͥ͢ Ϳ͵ ͨ ΅ ͧ ͤ͢ Ζ ΗΖ Σ Ζ Ο Δ Ζ Ζ ΘΦ ΝΒΥ ΠΣ ΅ ͑ ͷ ͟ͷ Τ Δ ʹ΅ ͥ ͿΠΟ ͞Κ Ο Χ ͺΟ ΡΦ Υ ͢ ͺΟ Χ ͞ͺΟ ΡΦ Υ ͣ ͿΠΟ ͞Κ Ο Χ ͺΟ ΡΦ Υ ͧ͢ ͺΟ Χ ͞ͺΟ ΡΦ Υ ͦ͢ ͷΖ Ζ Ε͞ͳΒ Δ Μ ͤ ͩ ʹ͢ ͪ Ͷ͢ ͢͢ ʹ ͣ ͦ ͵Ζ Β Ε͑΅ Κ ΞΖ ʹ ; Ͳ Ͳ ΅ ͵Ζ Β Ε͞΅ Κ ΞΖ ʹΠΟ Υ Σ ΠΝ Φ Υ ΡΦ Υ ͑ʹΠΟ Υ Σ ΠΝ ͢͡ Ͷͣ ͜ ͞ ͶͲ ͢ ͜ ͞ ͜ ͞ Έ; ʹ ; Ͳ Ͳ ΅ ͶͲ ͣ ͜ ͞ KSI-K003-001 4 STC494 INFORMATION The basic oscillator(switching)frequency is controlled by an external resistor (Rt) and capacitor(Ct). The relationship between the values of Rt Ct and frequency is shown in. The level of the sawtooth wave form is compared with an error voltage by the pulse width modulated comparator. The output of the PWM Comparator directs the pulse steering flip flop and the output control logic. The error voltage is generated by the error amplifier. The error amplifier boosts the voltage difference between the output and the 5V internal reference. See Figure7 for error amp sensing techniques. The second error amp is typically used to implement current limiting. The output control logic (Pin13) selects either push-pull or single-ended operation of the output transistors (see Figure6). The dead time control prevents on-state overlap of the output transistors as can be seen is Figure5. The dead time is approximately 3 to 5% of the total period if the dead time control(pin4) is grounded. This dead time can be increased by connecting the dead time control to a voltage up to 5 V. The frequency response of the error amps can be modified by using external resistors and capacitors. These components are typically connected between the compensation terminal (pin3) and the inverting input of the error amps(pin2 or pin15). The switching frequency of two or more S494 circuits can be synchronized. The timing capacitor, Ct is connected as shown in Figure8. Charging current is provided by the master circuit. Discharging is through all the circuits slaved to the master. Rt is required only for the master circuit. Operating Waveform 5 STC494 Test Circuit Fig.1Error Amplifier Test Circuit ͜ Fig.2 Current Limit sense Amplifier Test Circuit ͢͜ ͢͜ Ͷ Ͷ ·ͺͿ ·ͤ Ͳ; ͣ ͞ ͜ ͧ͢ ͜ Ͷ · Ͷͷ ͦ͢ ͣ ͞ ͧ͢ ͜ Ͷ · ͺͿ Ͳ; ͞ Ͳ; ͞ Fig. 3 Common-Emitter Configuration Test circuit and Waveform ͦ͢ ͞ Fig. 5 Dead-Time and Feedback Control Test Circuit ͦ͢· ͑ ͵ʹ ·ΔΔͮͦ͢· ͧͩ ʹ G G ͶΒ Δ Ι ͑ Π Φ Υ Ρ Φ Υ ΅ΣΒΟΤ ΚΤ ΥΠΣ ·Δ ͦ͢Ρ ͷ Ͷ G G G G ͖ͪ͡ ͖ͪ͡ ͖͢͡ ͖͢͡ ΅Σ ΅Η G ·ͤ Ͳ; · Ͷͷ ͞ ͦ͢͡ ͣ͢ ͣΈ ͥ ͵ͶͲ͵ ͩ ·ΔΔ ΅Ͷ΄΅ ʹ͢ ΅ͺ;Ͷ ͪ ͺΟΡΦΥΤ ͤ ͷͶͶ͵͑ͳͲʹͼ Ͷ͢ ͣ͢ͼ ͧ ΅ ͦ ʹ΅ ͢͢ ʹͣ ͢͡ ͢ ͟͢͡͡Φͷ ͣ ͙͚͜ Ͷͣ ͙͚͞ ͧ͢ ͙͚͜ ͦ͢ ͙͚͞ ͤ͢ Ά΅Ά΅ Ͷͷ ͥ͢ ʹͿ΅ͽ ͦ͡ͼ Ά΅ ͨ Ϳ͵ ͦ͢͡ ͣΈ Ά΅Ά΅͢ Ά΅Ά΅ͣ G G G G Fig. 4 Emitter-Follower Configuration Test circuit and waveform Voltage waveformG G ͦ͢· ͑͵ʹ ʹ G G G G G ͶΒΔΙ͑ΠΦΥΡΦΥ ΅ΣΒΟΤ ΚΤ ΥΠΣ ͖ͪ͡ ·Ͷ ͧͩ ͦ͢Ρͷ Ϳ͵ ͖ͪ͡ ͖͢͡ ͖͢͡ ΅Σ ΅Η G G 6 STC494 GG G APPLICATION CIRCUIT Fig. 6 Output Connections for Single-Ended and Push-Pull Configurations Fig. 7 Error Amplifier Sensing Techniques G ͢ ͩ G Ά΅Ά΅ ʹͿ΅ͽ G G ͪ ʹ͢ ΅͑Ά΅Ά΅ ·ͽ΅ͲͶ͑ͷ ΄Ί΄΅Ͷ; ͢ ͙͚ͧ͑͢͢͜ ·Π ʹ Ͷ͢ ͑͢΅͑ͦ͑͡͡ΞͲ͙;ͲΉ͚ ͣ ͢͢ ʹͣ G ͢͡ Ͷͣ ͑ͭ͑͡· ʹ͑ͭ͑ͥ· G ͙͚ͣͦ͑͢͞ · Ͷͷ G ͣ Ͷ Ͷ Ͳ; ͤ ΄ͺ΅ͺ·Ͷ͑Ά΅Ά΅ ·ͽ΅ͲͶ ΄ͺͿͽͶ͞ͶͿ͵Ͷ͵͑ʹͿͷͺΆͲ΅ͺͿ G G · Ͷͷ G G ͢ ͩ ͣͥ͟·ͭ·ʹͭ·Ͷͷ ͪ G ͣ ͢͢ Ά΅Ά΅ ʹͿ΅ͽ G G G ʹ͢ ͙͚ͧ͢͢ ͣͦ͑͡ΞͲ͙;ͲΉ͚ Ͷ͢ ʹͣ ͤ ͣ ͙͚ͣͦ͢ ͞ ͿͶͲ΅ͺ·Ͷ͑Ά΅Ά΅ ͢ ·ͽ΅ͲͶ ·Π ·Π͑ͮ͑͑͞· Ͷͷ ͢ ͣ ͣͦ͑͡ΞͲ͙;ͲΉ͚ ͢͡ ͜ Ͷͣ Ά΄͞Άͽͽ͑ʹͿͷͺΆͲ΅ͺͿ G ΅͑Ά΅Ά΅ ·ͽ΅ͲͶ͑ͷ ΄Ί΄΅Ͷ; G G Fig. 8 Slaving Tow or More Control Circuits · ΔΔ ͥ͢ · Ͷͷ ͧ ͦ ΅ ΅ · Ͷͷ ;Ͳ΄΅Ͷ ͧ ΅ ͦ ʹ΅ ΅͑Ͷ;ͲͺͿ͵Ͷ ͷ͑Ͷ Ͳ;ͽͺͷͺͶ ʹͺʹΆͺ΅ ΅͑Ͷ;ͲͺͿ͵Ͷ ͷ͑Ͷ Ͳ;ͽͺͷͺͶ ʹͺʹΆͺ΅ ʹ΅ ͥ͢ · Ͷͷ ʹ΅ Fig. 9Error Amplifier and Current Limit Sense Amplifier Output Circuits ΄ͽͲ· Ͷ ͙Ͳ͵͵ͺ΅ͺͿͲͽ ʹͺʹΆͺ΅΄͚ ͧ͟͡ΞͲ ΅͑ʹ;ͶͿ΄Ͳ΅ͺͿ Έ;͑ʹ;ͲͲ΅ ͺͿΆ΅ G G G 7 STC494 G Electrical Characteristic Curves G Fig. 1 VCE(sat) -IC Fig. 2 VCE -IE G G G G G G G G G G G G G Fig. 3 tOSC - RT Fig. 4 AVOL , Phase - f G ' G : G G G I G G G G G G G Fig. 5 ICC - VCC G G G G G G G G G G G G 8