UC2845

UNISONIC TECHNOLOGIES CO., LTD UC2844/45 HIGH PERFORMANCE CURRENT MODE PWM CONTROLLERS DESCRIPTION The UTC UC2844/2845 are high performance fixed frequency current mode controllers that specifically designed for Off-Line and DC to DC converter applications with minimal external parts count. The differences between UC2844 and UC2845 are the maximum duty cycle ranges and under-voltage lockout thresholds. The UC2844 ideally suited to off-line applications with UVLO thresholds of 16V(ON) and 10V(OFF), and UC2845 has UVLO thresholds of 8.5V(ON) and 7.6V(OFF) for lower voltage applications. LINEAR INTEGRATED CIRCUIT FEATURES * Operation output switching frequency up to 500 kHz * Output deadtime adjustable from 50% to 70% * Automatic feed forward compensation * Latching PWM for cycle-by-cycle current limiting * High current totem pole output * Internally trimmed reference with under voltage lockout * UVLO with hysteresis * Low startup and operating current *Pb-free plating product number: UC2844L/UC2845L ORDERING INFORMATION Order Number Lead Free Halogen Free UC2844L-S08-R UC2844G-S08-R UC2845L-S08-R UC2845G-S08-R Package SOP-8 SOP-8 Packing Tape Reel Tape Reel www.unisonic.com.tw Copyright © 2010 Unisonic Technologies Co., Ltd 1 of 7 QW-R103-051.A UC2844/45 PIN CONFIGURATION LINEAR INTEGRATED CIRCUIT PIN DESCRIPTION PIN NO 1 2 3 4 5 6 7 8 PIN NAME FUNCTION Compensation Error amplifier output, this pin is made available for loop compensation. Voltage Feedback, the inverting input of the Error Amplifier. It is normally connected to the VFB switching power supply output through a resistor divider. A voltage proportional to inductor current is connected to this input. The PWM uses this ISENSE information to terminate the output switch conduction. The Oscillator frequency and maximum output duty cycle are programmed by connecting RT/CT resistor RT to Vref and capacitor CT to ground. Operation to 1 MHz is possible. GND Power ground. This output directly drives the gate of a power MOSFET. Peak currents up to 1A are Output sourced and sunk by this pin. The output switches at one-half the oscillator frequency. VCC Positive supply. VREF Reference output, provides charging current for capacitor CT though resistor RT. UNISONIC TECHNOLOGIES CO., LTD www.unisonic.com.tw 2 of 7 Ver.A UC2844/45 BLOCK DIAGRAM LINEAR INTEGRATED CIRCUIT UNISONIC TECHNOLOGIES CO., LTD www.unisonic.com.tw 3 of 7 Ver.A UC2844/45 ABSOLUTE MAXIMUM RATINGS (Ta=25°C) LINEAR INTEGRATED CIRCUIT PARAMETER SYMBOL RATINGS UNIT Total Power Supply and Zener Current (ICC+Iz) 30 mA Output Current, Source or Sink (Note 2) IOUT 1.0 A Output Energy (Capacitive Load per cycle) W 5.0 μJ Current Sense and Voltage feedback Inputs VIN -0.3 ~ +5.5 V Error Amp Output Sink Current ISINK 10 mA Power Dissipation PD 862 mW Junction Temperature TJ +150 °C Operating Junction Temperature TJ(OPR) -40 ~ +120 °С Storage Temperature Range TSTG -65 ~ +150 °C Note: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.Maxmum package power dissipation limits must be observed. THERMAL DATA PARAMETER Thermal Resistance(Junction-to-Air) SYMBOL θJA RATINGS 145 UNIT °C/W ELECTRICAL CHARACTERISTICS (Ta=25°C, VCC=15V, RT=10k, CT=3.3nF, -40°C ≤ TA ≤ 120°C, unless otherwise specified) PARAMETER SYMBOL TEST CONDITIONS MIN REFERENCE SECTION Reference Output Voltage VREF IOUT=1.0mA,TJ=25 C 4.95 △VOUT VCC=12V ~ 25V Line Regulation △VOUT IOUT=1.0mA ~ 20mA Load Regulation Temperature Stability tS Total Output Variation over Line, VREF 4.9 Load, Temperature Output Noise Voltage eN f=10Hz ~ 10kHz, TJ=25°C Long Term Stability S TA=125°C for 1000 Hours Output Short Circuit Current ISC -30 OSCILLATOR SECTION Oscillator Voltage Swing VOSC Discharge Current IDSG VOSC=2.0V, TJ=25°C TJ=25°C, 47 Frequency fOSC TLOW ≤ TA ≤ THI 46 Frequency Change with Voltage ΔfOSC/ΔV VCC=12V ~ 25V Frequency Change with Temperature ΔfOSC/ΔT TLOW ≤ TA ≤ THI ERROR AMPLIFIER SECTION Voltage Feedback Input VFB VOUT=2.5V 2.45 High VOH RL=15k to ground, VFB=2.3V 5.0 Output Voltage Swing Low VOL RL=15k to VREF, VFB=2.7V Sink ISINK VOUT=1.1V, VFB=2.7V 2.0 Output Current Source ISOURCE VOUT=5.0V, VFB=2.3V -0.5 Input Bias Current II(BIAS) VFB=2.7V Open Loop Voltage Gain GVO VOUT=2.0V ~ 4.0V 65 Power Supply Rejection Ratio PSRR VCC=12V ~ 25V 60 Unity Gain Bandwidth GBW TJ=25°C 0.7 TYP 5.0 2.0 3.0 0.2 MAX 5.05 20 25 5.1 50 5 -85 1.6 10.8 52 0.2 5.0 2.50 6.2 0.8 12 -1.0 -0.1 90 70 1.0 UNIT V mV mV mV/°C V μV mV mA V mA 57 60 1.0 kHz % % V V mA -1.0 μA dB dB MHz -180 2.55 1.1 UNISONIC TECHNOLOGIES CO., LTD www.unisonic.com.tw 4 of 7 Ver.A UC2844/45 ELECTRICAL CHARACTERISTICS(Cont.) PARAMETER CURRENT SENSE SECTION Current Sense Input Voltage Gain (Note 2 & 3) Maximum Current Sense Input Threshold (Note 2) Input Bias Current Power Supply Rejection Ratio Propagation Delay OUTPUT SECTION Low Output Voltage High VOH SYMBOL GV VI(THR) II(BIAS) PSRR tPLH(IN/OUT) VOL LINEAR INTEGRATED CIRCUIT TEST CONDITIONS MIN 2.85 0.9 TYP 3.0 1.0 -2.0 70 150 0.1 1.6 13.5 13.4 0.1 50 50 MAX 3.15 1.1 -10 300 0.4 2.2 UNIT V/V V μA dB ns V V VCC=12V ~ 25V (Note4) Output Voltage with UVLO Activated VOL(UVLO) 1.1 V Output Voltage Rise Time tR 150 ns Output Voltage Fall Time tF 150 ns UNDERVOLTAGE LOCKOUT SECTION UC2844 15 16.0 17 Startup Threshold VTHR V UC2845 7.8 8.4 9.0 Minimum Operating UC2844 9.0 10.0 11.0 V VCC(MIN) Voltage After Turn-On 7.0 7.6 8.2 UC2845 PWM SECTION Max DCMAX 47 48 50 % Duty Cycle Min DCMIN 0 % TOTAL DEVICE Power Supply Zener Voltage VZ ICC=25mA 30 36 V UC2845 VCC=6.5V 0.5 1.0 Power Supply Current ICC mA (Note 4) VCC=14V UC2844 12 17 Note: 1. Low duty cycle pulse techniques are used during test to maintain junction temperature as close to ambient as possible. 2. This parameter is measured at the latch trip point with VFB=0V. 3. Comparator gain is defined as: ΔV Output Compensation AV= ΔV Current Sense Input 4. Adjust VCC above the startup threshold before setting to 15V. ISINK=20mA ISINK=200mA ISINK=20mA ISINK=200mA VCC=6.0V, ISINK=1.0mA CL=1.0nF,TJ=25°C CL=1.0nF,TJ=25°C 13 12 UNISONIC TECHNOLOGIES CO., LTD www.unisonic.com.tw 5 of 7 Ver.A UC2844/45 TYPICAL CHARACTERISTICS Timing Resistor vs. Oscillator Frequency 100 50 Timing Resistor, RT (kΩ) 20 75 Percent Output Deadtime, DT (%) 10 0p TA = 25℃ F 20 0p 50 F 0p F 1.0 2.0 nF nF 5.0 nF C T= 10 nF VCC = 15V LINEAR INTEGRATED CIRCUIT Output Deadtime vs. Oscillator Frequency 1.0nF 70 5.0nF 65 CT = 10nF 2.0nF 10 5.0 60 2.0 Note: Output Switches At One-Half The Oscillator Frequency 55 500pF 20k 50k 100k 200k Oscillator Frequency, IOSC (Hz) 100pF 200pF 1.0M 1.0 10k 20k 50k 100k 200k 500k 1.0M 50 10k 500k Oscillator Frequency, IOSC (Hz) Error Amp Open Loop Gain Phase vs. Frequency Current Sense Input Threshold, VIN(THR) (V) 100 Open Loop Voltage Gain, GV (dB) 80 Gain 60 40 Phase 20 0 -20 120 150 180 10M VCC = 15V VOUT = 2.0V ~ 4.0V RL = 100k TA = 25℃ Current Sense Input Threshold vs. Error Amp Output Voltage 0 30 Excess Phase Degrees, φ 60 90 1.2 1.0 TA = 125℃ 0.8 TA = 25℃ 0.6 0.4 TA = -55℃ 0.2 0 VCC = 15V 10 100 1.0k 10k 100k 1.0M 0 2.0 4.0 6.0 8.0 Frequency, f (Hz) Error Amp Output Voltage, VOUT (V) UNISONIC TECHNOLOGIES CO., LTD www.unisonic.com.tw 6 of 7 Ver.A UC2844/45 TYPICAL CHARACTERISTICS(Cont.) LINEAR INTEGRATED CIRCUIT Output Saturation Voltage, VO(SAT) (V) Supply Current, ICC (mA) UCX845 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 UCX844 7 of 7 Ver.A