GSC3842

ISSUED DATE :2003/05/20 REVISED DATE :2005/10/05C GSC3842 Description HIGH PERFORMANCE CURRENT MODE CONTROLERS The GSC3842 is high performance fixed frequency current mode controllers. This is specifically designed for Off-Line and DC To DC converter applications offering the designer a cost-effective solution with minimal external components. These integrated circuits feature a trimmed oscillator for precise duty cycle control. A temperature compensated reference, high gain Error amplifier, current sensing comparator, and a high current totem pole output ideally suited for driving a power MOSFET. Also Included are protective features consisting of input and reference undervoltage lockouts each with hysteresis, cycle-by-cycle current limiting, programmable output deadtime, and latch for single pulse metering. *Trimmed Oscillator for Precise Frequency Control *Oscillator Frequency Guaranteed at 250kHz *Current Mode Operation to 500kHz *Automatic Feed Forward Compensation *latching PWM for Cycle-By-Cycle Current Limiting *Internally Trimmed Reference with Undervoltage Lockout *High Current Totem Pole Output *Undervoltage Lockout with Hysteresis *Low Startup and Operating Current Features Package Dimensions REF. A B C D E F Millimeter Min. Max. 5.80 4.80 3.80 0C 0.40 0.19 6.20 5.00 4.00 8C 0.90 0.25 REF. M H L J K G Millimeter Min. Max. 0.10 0.25 0.35 0.49 1.35 1.75 0.375 REF. 45 C 1.27 TYP. SOP-8L Function Pin1:Compensation Pin2:Voltage Feedback Pin3:Current Sense Pin4:RT/CT Pin5:Ground Pin6:Output Pin7:Vcc Pin8:Vref Description This pin is the Error Amplifier output and is made available for loop compensation. This is the inverting input of the Error Amplifier. It’s normally connected to the Switching power supply output through a resistor divider. A voltage proportional to inductor current is connected to this input .The PWM uses this information to terminate the output switch conduction. The oscillator frequency and maximum output duty cycle are programmed by connecting resistor RT to Vref and capacitor CT to ground .Operation 500kHz is possible. This pin is the combined control circuitry and power ground. This output directly drives the gate of a power MOSFET. Peak currents up to 1 A are sourced and sunk by this pin. This pin is the positive supply of the control IC. This is the reference output .It provides charging current for capacitor CT through resistor RT. Absolute Maximum Ratings at Ta = 25 : Parameter Total power Supply and Zener current Output current, source or sink(note1) Output energy(capacitive load per cycle) Current sense and voltage feedback inputs Error Amplifier Output Sink Current Symbol (ICC+Iz) Io W Vin Io Value 30 1.0 5.0 -0.3 to 5.5 10 Unit mA A J V mA GSC3842 Page: 1/9 ISSUED DATE :2003/05/20 REVISED DATE :2005/10/05C P ower Dissipation at Thermal characteristics Storage Temperature Range Operating Junction Temperature Operating ambient Temperature PD P JA Tstg TJ TA (0 : 702 178 -65 to 150 +150 0~+70 mW : /W : : : Electrical Characteristics Parameter Reference Section Output Voltage Line Regulation Load Regulation Temperature. Stability Total Output Variation Output Noise Voltage Long Term Stability Output Short Circuit current Oscillator Section Frequency TA 70 : , Vcc=15V [note 2], R T=10k, C T=3.3nF, unless otherwise specified) Symbol Test Conditions Tj=25 : ,Io=1mA Vcc=12V to 25V Io=1mA to 20mA Line, Load, Temperature F=10kHz to 10Hz,Tj=25 : TA=125 : ,1000Hrs Tj=25 : TA=0 : to 70 : Tj=25 : (RT =6.2k,CT =1.0nF) Min 4.90 4.82 -30 49 48 225 7.8 7.6 2.42 65 0.7 60 2.0 -0.5 5.0 2.85 0.9 13 12 14.5 8.5 Typ 5 2.0 3.0 0.2 50 5 -85 52 250 0.2 0.5 1.6 8.3 2.50 -0.1 90 1.0 70 12 -1.0 6.2 0.8 3.0 1.0 70 -2 150 0.1 1.6 13.5 13.4 0.1 50 50 16 10 Max 5.1 20 25 5.18 -180 55 56 275 1.0 8.8 8.8 2.58 -2.0 1.1 3.15 1.1 -10 300 0.4 2.2 1.1 150 150 17.5 11.5 % % V mA KHz Unit V mV mV mV/ : V V mV mA VREF Regline Regload Ts VREF Vn S ISC Frequency Change with Voltage Frequency Change with Temperature Oscillator Voltage Swing(Peak to Peak) Discharge Current Error Amplifier Section Voltage Feedback Input Input Bias Current Open Loop Voltage Gain Unity Gain Bandwidth P ower Supply Rejection Ratio Output Sink Current Output Source Current Output Voltage Swing High State Output Voltage Swing Low State Current Sense section Current Sense Input Voltage gain P ower Supply Rejection Ratio Input Bias Current Propagation Delay Output Low Voltage Output High Level Output Voltage with UVLO Activated Output Voltage Rise Time Output Voltage Fall Time Under-Voltage Lockout Section Startup Threshold fosc/ V fosc/ T VOSC Idischg Vcc=12V to 25V TA = 0 : to 70 : Tj=25 : TA = 0 : to 70 : Vo =2.5V VFB=5.0V Vo=2V to 4V Tj=25 : Vcc=12V to 25V Vo=1.1V,VFB=2.7V Vo=5.0V,VFB=2.3V VFB=2.3V,RL =15K to GND VFB=2.7V,RL =15K to Vref (Note 3,4) (Note 3) VCC= 12 to 25V (Note 3) - VFB IIB AVOL BW PSRR Isink Isource VoH VOL Av PSRR IIB V A dB MHz dB mA mA V V V/V V dB A ns V V V V V ns ns V V Maximum Current Sense Input Threshold Vth Tplh(in/out) Current Sense Input to Output VOL Isink=20mA Isink=200mA VOH Isource=20mA Isource=200mA VOL (UVLO) tr tr Vth VCC=6.0V,Isink=1.0mA Tj=25 : ,CL=1nF Tj=25 : ,CL=1nF - Min. Operating Voltage After Turn-on(VCC) VCC(min) GSC3842 Page: 2/9 ISSUED DATE :2003/05/20 REVISED DATE :2005/10/05C PWM Section Maximum Duty Cycle Minimum Duty Cycle Total Device P ower Startup Supply Current P ower Operating Supply Current P ower Supply Zener Voltage ICC+IC ICC+IC Vz VCC=14V N ote 2 ICC=25mA 30 0.3 12 36 0.5 17 mA mA V DC(MAX) DC(MIN) 94 96 0 % % N ote 1: Maximum Package power dissipation limits must be observed. Note 2: Adject Vcc above the Startup threshold before setting to 15V. Note 3: This parameter is measured at the latch trip point with VFB=0V. Note 4: Comparator gain is defined as:: AV V Output Compensation V Current Sense Input Characteristics Curve GSC3842 Page: 3/9 ISSUED DATE :2003/05/20 REVISED DATE :2005/10/05C GSC3842 Page: 4/9 ISSUED DATE :2003/05/20 REVISED DATE :2005/10/05C GSC3842 Page: 5/9 ISSUED DATE :2003/05/20 REVISED DATE :2005/10/05C Application Information GSC3842 Page: 6/9 ISSUED DATE :2003/05/20 REVISED DATE :2005/10/05C GSC3842 Page: 7/9 ISSUED DATE :2003/05/20 REVISED DATE :2005/10/05C GSC3842 Page: 8/9 ISSUED DATE :2003/05/20 REVISED DATE :2005/10/05C Important Notice: All rights are reserved. Reproduction in whole or in part is prohibited without the prior written approval of GTM. GTM reserves the right to make changes to its products without notice. GTM semiconductor products are not warranted to be suitable for use in life-support Applications, or systems. GTM assumes no liability for any consequence of customer product design, infringement of patents, or application assistance. Head Office And Factory: Taiwan: No. 17-1 Tatung Rd. Fu Kou Hsin-Chu Industrial Park, Hsin-Chu, Taiwan, R. O. C. TEL : 886-3-597-7061 FAX : 886-3-597-9220, 597-0785 China: (201203) No.255, Jang-Jiang Tsai-Lueng RD. , Pu-Dung-Hsin District, Shang-Hai City, China TEL : 86-21-5895-7671 ~ 4 FAX : 86-21-38950165 GSC3842 Page: 9/9