Vref. Good Logic 1/3Vref CURRENT SENSE COMPARATOR OSCILLATOR

Transcription

1 UTC UCA / A CURRENT MODE PWM CONTROL CIRCUITS DESCRIPTION The UTC UCA/A provide the necessary functions to implement off-line or DC to DC fixed frequency current mode, controlled switching circuits with a minimal external part count SOP- FEATURES *Low external part count. *Low start up current ( Typical 0.mA ) *Automatic feed forward compensation *Pulse-by-Pulse current limiting *Under-voltage lockout with hysteresis *Double pulse Suppression *High current totem pole output to drive MOSFET directly *Internally trimmed band gap reference *00kHz operation DIP- *Pb-free plating product number: UCAL/UCAL BLOCK DIAGRAM Vref V REF S/R Internal Bias /Vref Vref Good Logic /Vref CURRENT SENSE COMPARATOR U.V.L.O GND VFB COMP ERROR AMPLIFIER V R PWM LATCH 6 OUTPUT S CURRENT SENSE RT/CT OSCILLATOR GND ABSOLUTE MAXIMUM RATINGS(Ta= C) PARAMETER SYMBOL VALUE UNIT Supply Voltage(Low Impedance Source) VCC 0 V Supply Voltage(Icc<0mA) Self Limiting V Output Current ( Peak ) Io +- A Output Energy(capacity Load) µj Analog Inputs(pin,) VI(ANA) -0. ~ +6. V Error Amplifier Output Sink Current ISINK(EA) ma Power Dissipation PD DIP- at Tamb<= C.0 W SOP- at Tamb<= C 0. W Lead Temperature( Soldering Sec ) Tlead 00 C UTC UNISONIC TECHNOLOGIES CO., LTD. QW-R-00,B

2 UTC UCA / A (continued) PARAMETER SYMBOL VALUE UNIT Storage Temperature Tstg -6 ~ +0 C Operating junction temperature Tj +0 C Note : Ta> C, PD derated with mw/ C. ELECTRICAL CHARACTERISTICS (0 C <=Ta<=0 C,VCC=V,RT=kΩ,CT=.nF,unless otherwise specified) PARAMETER SYMBOL TEST CONDITIONS MIN TYP MAX UNIT Reference Section Output Voltage VREF Tj= C,Io=mA.9. V Line Regulation VREF <=VIN<=V 6 0 mv Load Regulation VREF <=Io=0mA 6 mv Temperature Stability (Note ) mv/ C Total Output Variation Line, Load, Temp(note ).. V Output Noise Voltage Vosc Hz<=f<=kHz,Tj= C (note ) 0 uv Long Term Stability Ta= C,00Hrs(note ) mv Output Short Circuit ISC ma Oscillator Section Initial Accuracy f Tj= C khz Voltage Stability f/ <=<=V 0. % Temperature Stability Tmin<=TA<=Tmax(note ) % Amplitude Vosc Vpin peak to peak. V Error Amplifier Section Input Voltage VI(EA) Vpin =.V..0. V Input Bias Current IBIAS µa AVOL <=Vo<=V db Unity Gain Bandwidth Tj= C (note ) 0. MHz PSRR I<=<=V 60 0 db Output Sink Current Isink Vpin =.V,Vpin =.V 6 ma Output Source Current Isource Vpin =.V,Vpin =V ma Vout High VOH Vpin =.V, RL=kΩ to GND 6 V Vout Low VOL Vpin =.V,Vpin =.V 0.. V Current Sense section Gain GV (note,).. V/V Maximum Input signal VI(MAX) Vpin =V( note ) 0.9. V PSRR <=<=V 0 db Input Bias Current IBIAS - - µa Delay to Output Vpin =0 to V 0 00 ns Output Section Output Low Level VOL Isink=0mA V Isink=00mA.. V Output High Level VOH Isource=0mA. V Isource=00mA. V Rise Time tr Tj= C,CL=nF(note ) 0 0 ns Fall Time tf Tj= C,CL=nF(note ) 0 0 ns Under-Voltage Lockout Output Section Start Threshold VTH(ST) UTCA. 6. V UTCA.. 9 V Min. Operating Voltage VOPR(min) After Turn On UTCA.. UTCA.6. V PWM Section UTC UNISONIC TECHNOLOGIES CO., LTD. QW-R-00,B

3 UTC UCA / A PARAMETER SYMBOL TEST CONDITIONS MIN TYP MAX UNIT Maximum Duty Cycle D(MAX) % Minimum Duty Cycle D(MIN) 0 % Total Standby Current Start-up Current IST ma Operating Supply Current ICC(opr) Vpin =Vpin =0V ma Zener Voltage Vz Icc=mA V note :These parameters, although guaranteed,are not 0% tested in production. note :Parameters measured at trip point of latch with Vpin =0. note :Gain defined as: A= Vpin Vpin ; 0<=Vpin<=0.V note :Adjust above the start threshold before setting at V. OPEN-LOOP LABORATORY TEST FIXTURE Vref.kΩ.kΩ Error Amp Adjust Isense Adjust RT kω 0kΩ 6 0. µf 0. µf A kω / W OUTPUT CT High peak current associated with capacity loads necessitate careful grounding techniques. Timing and bypass capacitors should be connected close to pin in single point GND. The transistor and kω potentio-meter are used to sample the oscillator waveform and apply an adjustable Ramp to Pin. UNDER-VOLTAGE LOCKOUT Icc ON/OFF Command to rest of IC <ma Von=6V Voff=V <ma Voff Von During Under-Voltage Lockout, the output driver is biased to a high impedance state. Pin 6 should be shunt to GND with a bleeder resistor to prevent activating the power switch with output leakage currents. UTC UNISONIC TECHNOLOGIES CO., LTD. QW-R-00,B

4 UTC UCA / A ERROR AMPLIFIER CONFIGURATION.V 0.mA Zi Zf CURRENT SENSE CIRCUIT Error amplifier can source or sink up to 0.mA Rs R Is C Error Amplifier R R V Current Sense Comparator SLOPE COMPENSATION Peak current (Is) determined by the formula: Ismax=V/Rs. A small RC filter be required to suppress switch transients. 0. µf CT RT R R C Isense Rsense A fraction of the oscillator ramp can be resistively summed with the current sense signal to provide slope compensation for converts requiring duty cycles over 0%.Note that capacitor C, forms a filter with R to suppress the leading edge switch spikes. UTC UNISONIC TECHNOLOGIES CO. LTD QW-R-00,B

5 UTC UCA / A OSCILLATOR SECTION V RT CT Large RT Small CT Small RT Large CT INTERNAL CLOCK V INTERNAL CLOCK Dead time VS CT(RT>kΩ) Timing Resistance Vs Frequency 0 0 td (µs) RT (kω) CT=nF CT=.nF CT=.nF CT=nF CT=nF CT=nF CT=0nF 0. 0 CT (nf) Frequency (Hz) 6 SHUTDOWN TECHNIQUES Shutdown 0Ω kω 00Ω Shutdown To current Sense resistor Shutdown UTC UCA can be accomplished by two methods; either raise pin above V or pull Pin below a voltage two diode drops above ground. Either method caused the output of PWM comparator to be high(refer to block diagram).the PWM latch is reset dominant so that the output will remain low until the next clock cycle after the shutdown condition at pins and/or is removed. In one example, an externally latched shut down may be accomplished by adding an SCR which be reset by cycling below the lower UVLO threshold. At this point the reference turns off allowing the SCR to reset. UTC UNISONIC TECHNOLOGIES CO. LTD QW-R-00,B

6 UTC UCA / A TYPICAL PERFORMANCE CHARACTERISTICS 0 Saturation Voltage (V) =V Ta=+ C Ta=- C Voltage Gain (db) PHASE (Degree) Output Current (Sourse or Sink Current) (A) Frequency (Hz) 6 Output Saturation Characteristics Error Amplifier Open-Loop Frequency Response Vref Temperature Drift Istart Temperature Drift.0 0 Vref (V).0 =V Io=mA 00 =9V Istart (ma) Temperature ( C) Temperature ( C) Icc Temperature Drift Icc (ma) =V Io=mA Temperature ( C) UTC UNISONIC TECHNOLOGIES CO. LTD 6 QW-R-00,B

7 UTC UCA / A UTC assumes no responsibility for equipment failures that result from using products at values that exceed, even momentarily, rated values (such as maximum ratings, operating condition ranges, or other parameters) listed in products specifications of any and all UTC products described or contained herein. UTC products are not designed for use in life support appliances, devices or systems where malfunction of these products can be reasonably expected to result in personal injury. Reproduction in whole or in part is prohibited without the prior written consent of the copyright owner. The information presented in this document does not form part of any quotation or contract, is believed to be accurate and reliable and may be changed without notice. UTC UNISONIC TECHNOLOGIES CO. LTD QW-R-00,B