UNISONIC TECHNOLOGIES CO., LTD UC2843B Preliminary LINEAR INTEGRATED CIRCUIT HIGH-PERFORMANCE CURRENT-MODE PWM CONTROLLERS DESCRIPTION The UTC UC2843B provides off-line or DC-DC fixed-frequency current-mode control design with minimum external components. Internally-implemented circuits include an under-voltage lockout (UVLO) and a precision reference with accuracy at the error amplifier input. The UTC UC2843B also contain internal circuits which include a pulse width modulation (PWM) comparator providing current-limit control, logic ensuring latched operation, and a totem-pole output stage designed to source or sink high-peak current. The output stage is low when it is in off-state condition and suitable for N-channel MOSFETs driving. The UTC UC2843B also has following advantages: the start-up current lower than 0.5mA while the oscillator discharge current is specified to 8.3mA (Typ.). In UVLO conditions, the output has a maximum saturation voltage of 1.2V when sinking 10mA@VCC = 5V. The typical UVLO threshold of the UTC UC2843B is 8.4V (on) and 7.6V (off) and can operate to duty cycles approximately 100%. * * * * * * * * * FEATURES Current mode operation:500 kHz Low start-up current value<0.5mA Latching PWM for cycle-by-cycle current limiting Trimmed oscillator discharge current Automatic feed-forward compensation Internally trimmed reference with UVLO High-current totem-pole output UVLO with hysteresis Double-pulse suppression Halogen free ORDERING INFORMATION Ordering Number UC2843BG-S08-R Package SOP-8 www.unisonic.com.tw Copyright © 2009 Unisonic Technologies Co., Ltd Packing Tape Reel 1 of 9 QW-R103-048.a UC2843B Preliminary PIN CONFIGURATION COMP 1 VFB 2 LINEAR INTEGRATED CIRCUIT 8 VREF 7 VCC ISENSE 3 6 OUTPUT RT/CT 4 5 GND PIN DESCRIPTION PIN NO. 1 PIN NAME COMP 2 VFB 3 ISENSE 4 RT/CT 5 GND 6 OUTPUT 7 VCC 8 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 is 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 to 500 kHz 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 1.0 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. UNISONIC TECHNOLOGIES CO., LTD www.unisonic.com.tw 2 of 9 QW-R103-048.a UC2843B Preliminary LINEAR INTEGRATED CIRCUIT BLOCK DIAGRAM UNISONIC TECHNOLOGIES CO., LTD www.unisonic.com.tw 3 of 9 QW-R103-048.a UC2843B Preliminary LINEAR INTEGRATED CIRCUIT ABSOLUTE MAXIMUM RATING(Ta=25°C, unless otherwise specified) PARAMETER SYMBOL RATINGS UNIT Supply Voltage (Low impedance source) VCC 30 V Analog Input Voltage (VFB and ISENSE) VIN -0.3~+6.3 V Supply Current ICC 30 mA Output Current IOUT ±1 A Error Amplifier Output Sink Current IO(SINK) 10 mA Power Dissipation PD 702 mW Output Energy (Capacitive load) W 5 μJ Junction Temperature TJ 150 °C Operating Temperature TOPR -40~+85 °C Storage Temperature TSTG -65~+150 °C Notes: 1. Absolute maximum ratings are those values beyond which the device could be permanently damaged. Absolute maximum ratings are stress ratings only and functional device operation is not implied. 2. All voltages are concerning the device GND terminal. THERMAL DATA PARAMETER Junction to Ambient SYMBOL θJA MIN TYP MAX 178 UNIT °C/W MIN TYP MAX 30 5.5 5.5 30 25 200 -20 500 +85 UNIT V V V V mA mA mA kHz °C RECOMMENDED OPERATING CONDITIONS PARAMETER Supply Voltage Input Voltage RT/CT VFB and ISENSE Output Voltage (OUTPUT) Supply Current, Externally Limited Output Current Reference Output Current Oscillator Frequency Operating Temperature SYMBOL VCC VIN VOUT ICC IOUT IO(REF) fOSC Ta UNISONIC TECHNOLOGIES CO., LTD www.unisonic.com.tw 0 0 0 100 -40 4 of 9 QW-R103-048.a UC2843B Preliminary LINEAR INTEGRATED CIRCUIT ELECTRICAL CHARACTERISTICS (VCC = 15 V, RT = 10kΩ, CT = 3.3nF, TJ=25°C, unless otherwise specified) PARAMETER REFERENCE SECTION Reference Output Voltage Line Regulation Load Regulation Average Temperature Coefficient Of Output Voltage Total Output Variation Output Noise Voltage Long Term Stability Output Short Circuit Current OSCILLATOR SECTION Frequency SYMBOL VREF ΔVOUT ΔVOUT Frequency Change with Temperature Oscillator Voltage Swing Discharge Current ERROR-AMPLIFIER SECTION Voltage Feedback Input Input Bias Current Open Loop Voltage Gain Unity Gain Bandwidth Power Supply Rejection Ratio Output Sink Current Output Source Current Output Voltage Swing High State CURRENT-SENSE SECTION Current Sense Input Voltage Gain Maximum Current Sense Input Threshold Power Supply Rejection Ratio Input Bias Current Propagation Delay OUTPUT SECTION VREF eN VCC =12V~25V, IOUT =1mA~20mA f = 10Hz~10kHz, TJ =25°C TJ=25°C FOR 1000 hours ISC ΔfOSC ΔV ΔfOSC ΔT VOSC IDISC VFB II(BIAS) GVO GBW PSRR ISINK ISOURCE VOH VOL MAX UNIT 4.95 5 6 6 5.05 20 25 V mV mV 0.2 0.4 mV/°C 5.1 TJ =25°C, RT =62kΩ, CT =1nF, Min =225 kHz, Max =275 kHz TJ = Full range 4.9 -30 50 5 -100 25 -180 V μV mV mA 49 52 55 kHz 56 kHz 1 % 48 VCC = 12V ~ 25V 0.2 TJ = Full range 5 Peak to peak TJ =25°C, RT/CT =2V RT/CT =2V 7.8 7.5 COMP =2.5V 2.45 VOUT =2V~4V 65 0.7 60 2 -0.5 5 VCC =12V~25V VFB =2.7V, COMP=1.1V VFB =2.3V, COMP =5V VFB =2.3V, RL =15kΩ to GND VFB =2.7V, RL =15kΩ to GND 1.7 8.3 % 8.8 8.8 V mA mA 2.5 -0.3 90 1 70 6 -0.8 6 0.7 2.55 -1 1.1 V μA dB MHz dB mA mA V V (Note 2,3) 2.85 3 3.15 V/V VTH COMP =5V (Note 2) 0.9 1 1.1 V 70 -2 150 -10 300 dB μA ns 13.5 13.5 0.1 1.5 0.4 2.2 V V V V PSRR II(BIAS) tD VOH Low-Level Output Voltage VOL VCC =12V~25V (Note 2) VFB =0V~2V IOH =-20mA IOH =-200mA IOL =20mA IOL =200mA 13 12 VUVLO VCC =5V, IOL=1mA 0.7 1.2 V tR tF CL =1nF, TJ = 25°C CL =1nF, TJ = 25°C 50 50 150 150 ns ns UNISONIC TECHNOLOGIES CO., LTD www.unisonic.com.tw TYP GV High-Level Output Voltage Under-Voltage Lockout Output Voltage Output Voltage Rise Time Output Voltage Fall Time IOUT =1mA, TJ =25°C VCC = 12V~25V IOUT = 1mA~20mA MIN TS fOSC Frequency Change with Voltage TEST CONDITIONS 5 of 9 QW-R103-048.a UC2843B Preliminary LINEAR INTEGRATED CIRCUIT ELECTRICAL CHARACTERISTICS (Cont.) PARAMETER SYMBOL TEST CONDITIONS MIN UNDERVOLTAGE-LOCKOUT SECTION Startup Threshold VTH 7.8 Minimum Operating Voltage VCC(MIN) 7 After Start-Up PULSE-WIDTH MODULATOR SECTION Maximum Duty Cycle DC(MAX) 94 Minimum Duty Cycle DC(MIN) SUPPLY VOLTAGE Power Startup Supply Current ICC+IC Power Operating Supply Current ICC+IC VFB and ISENSE at 0V Power Supply Zener Voltage VZ ICC =25mA 30 Notes: 1. Adjust VCC above the start threshold before setting it to 15V. 2. Measured at the trip point of the latch, with VFB at 0V. 3. Measured between ISENSE and COMP, with the input changing from 0V ~ 0.8V. UNISONIC TECHNOLOGIES CO., LTD www.unisonic.com.tw TYP MAX UNIT 8.4 9 V 7.6 8.2 V 96 100 0 % % 0.3 11 34 0.5 17 mA mA V 6 of 9 QW-R103-048.a UC2843B Preliminary LINEAR INTEGRATED CIRCUIT APPLICATION INFORMATION Error amplifier (EA) configuration circuit: 0.5mA 2.5V EA VFB Z1 Z2 Error Amplifier COMP Note: Error amplifier can source or sink up to 0.5mA. Current-sense circuit: Notes: 1. Peak current (IS) is determined by the formula: IS(max) = 1 V/RS 2. A small RC filter formed by resistor Rf and capacitor Cf may be required to suppress switch transients. The oscillator frequency is set using the circuit: VREF RT RT/CT CT GND The frequency is calculated as followed: f = 1 / RTCT For RT > 5kΩ: f = 1.72 / RTCT UNISONIC TECHNOLOGIES CO., LTD www.unisonic.com.tw 7 of 9 QW-R103-048.a UC2843B Preliminary LINEAR INTEGRATED CIRCUIT APPLICATION INFORMATION(Cont.) Open-Loop Laboratory Test Fixture In the open-loop laboratory test fixture, high peak currents and loads need grounding techniques. The transistor and 5-kΩ potentiometer sample the oscillator waveform, applying an adjustable ramp to the ISENSE terminal. Timing and bypass capacitors should be connected closely to the GND terminal in a single-point ground. Shutdown Technique The PWM controller can be shut down through two methods: the one is raising voltage (above 1 V) at ISENSE, the other is pulling the COMP terminal below a voltage two diode drops above ground. Either method can leave the output of the PWM comparator high (refer to block diagram). To reset the PWM latch is dominant so the output can stay low in the case of the next clock cycle is coming and the COMP or ISENSE terminal is removed beyond this shutdown condition. For example, an externally-latched shutdown can be accomplished by adding an SCR reset by cycling VCC below the lower UVLO threshold. So the reference turns off then allows the SCR to reset at this condition. 1kΩ VREF COMP Shutdown 330Ω ISENSE 500Ω To Current-Sense Resistor UNISONIC TECHNOLOGIES CO., LTD www.unisonic.com.tw 8 of 9 QW-R103-048.a UC2843B Preliminary LINEAR INTEGRATED CIRCUIT APPLICATION INFORMATION(Cont.) Shutdown Technique (cont.) A fraction of the triangular-wave oscillator can be summed resistively with the current-sense signal providing slope compensation for converters, which requiring duty cycles over 50%. Please note that capacitor C forms a filter with R2 to suppress the leading-edge switch spikes. VREF 0.1µF RT RT/CT CT R1 ISENSE R2 ISENSE C RSENSE 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. UNISONIC TECHNOLOGIES CO., LTD www.unisonic.com.tw 9 of 9 QW-R103-048.a