UC3844M/TR

UC3844/3845 HIGH PERFORMANCE CURRENT MODE PWM CONTROLLERS „ DESCRIPTION The HG UC3844/3845 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 UC3844 and UC3845 are the maximum duty cycle ranges and under-voltage lockout thresholds. The UC3844 ideally suited to off-line applications with UVLO thresholds of 16V(ON) and 10V(OFF), and UC3845 has UVLO thresholds of 8.5V(ON) and 7.6V(OFF) for lower voltage applications. „ 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 „ PIN CONFIGURATION http://www.hgsemi.com.cn 1 2016 APR UC3844/3845 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. BLOCK DIAGRAM http://www.hgsemi.com.cn 2 2016 APR UC3844/3845 „ ABSOLUTE MAXIMUM RATINGS (Ta=25°C) PARAMETER Total Power Supply and Zener Current Output Current, Source or Sink (Note 2) Output Energy (Capacitive Load per cycle) Current Sense and Voltage feedback Inputs Error Amp Output Sink Current RATINGS UNIT 30 mA 1.0 A 5.0 μJ -0.3 ~ +5.5 V 10 mA SOP-8 862 mW Power Dissipation PD DIP-8 1250 mW Junction Temperature TJ +150 °C Operation Temperature Range TOPR 0 ~ 70 °C 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. „ SYMBOL (ICC+Iz) IOUT W VIN ISINK THERMAL DATA PARAMETER Thermal Resistance(Junction-to-Air) „ SYMBOL SOP-8 DIP-8 θJA RATINGS 145 100 UNIT °C/W °C/W ELECTRICAL CHARACTERISTICS (Ta=25°C, VCC=15V, RT=10k, CT=3.3nF, 0°C ≤ TA ≤ PARAMETER SYMBOL REFERENCE SECTION Reference Output Voltage VREF △VOUT Line Regulation △VOUT Load Regulation Temperature Stability Total Output Variation over Line, Load, Temperature Output Noise Voltage Long Term Stability Output Short Circuit Current OSCILLATOR SECTION Oscillator Voltage Swing Discharge Current VOSC IDSG Frequency fOSC Frequency Change with Voltage Frequency Change with Temperature ERROR AMPLIFIER SECTION Voltage Feedback Input High Output Voltage Swing Low Sink Output Current Source Input Bias Current Open Loop Voltage Gain Power Supply Rejection Ratio Unity Gain Bandwidth http://www.hgsemi.com.cn 70°C, unless otherwise specified) TEST CONDITIONS MIN IOUT=1.0mA,TJ=25 C VCC=12V ~ 25V IOUT=1.0mA ~ 20mA 4.9 tS VREF eN S ISC ΔfOSC/ΔV ΔfOSC/ΔT VFB VOH VOL ISINK ISOURCE II(BIAS) GVO PSRR GBW TYP MAX UNIT 5.0 2.0 3.0 0.2 5.1 20 25 V mV mV mV/°C 5.18 V -180 μV mV mA 4.82 f=10Hz ~ kHz, TJ=25°C TA=125°C for 1000 Hours -30 VOSC=2.0V, TJ=25°C TJ=25°C, 0°C ≤ TA ≤ 70°C VCC=12V ~ 25V 0°C ≤ TA ≤ 70°C VOUT=2.5V RL=15k to ground, VFB=2.3V RL=15k to VREF, VFB=2.7V VOUT=1.1V, VFB=2.7V VOUT=5.0V, VFB=2.3V VFB=2.7V VOUT=2.0V ~ 4.0V VCC=12V ~ 25V TJ=25°C 3 47 46 50 5 -85 1.6 10.8 52 0.2 5.0 2.42 5.0 2.0 -0.5 65 60 0.7 2.50 6.2 0.8 12 -1.0 -0.1 90 70 1.0 V mA 57 60 1.0 2.58 1.1 kHz % % V V mA -2.0 μA dB dB MHz 2016 APR UC3844/3845 „ 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 SYMBOL MIN TYP MAX UNIT GV 2.85 3.0 3.15 V/V VI(THR) 0.9 1.0 1.1 V -2.0 70 150 -10 μA dB ns II(BIAS) PSRR TEST CONDITIONS VCC=12V ~ 25V (Note4) tPLH(IN/OUT) Low VOL High VOH Output Voltage 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 12 300 0.1 1.6 13.5 13.4 0.1 50 50 0.4 2.2 V V 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 UC3844 14.5 16.0 17.5 Startup Threshold VTHR V UC3845 7.8 8.4 9.0 Minimum Operating UC3844 8.5 10.0 11.5 V VCC(MIN) Voltage After Turn-On 7.0 7.6 8.2 UC3845 PWM SECTION Max DCMAX 47 48 50 % Duty Cycle Min DCMIN 0 % TOTAL DEVICE Power Supply Zener Voltage VZ ICC=25mA 30 36 V UC3845 V =6.5V 0.5 1.0 Power Supply Current CC ICC mA (Note 4) VCC=14V 12 17 UC3844 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. „ TYPICAL CHARACTERISTICS Timing Resistor vs. Oscillator Frequency VCC = 15V 20 10 5.0 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 50 Timing Resistor, RT (kΩ) Output Deadtime vs. Oscillator Frequency 75 100 2.0 Note: Output Switches At One-Half The Oscillator Frequency 1.0 10k 20k 50k 100k 200k 2.0nF 5.0nF 65 CT = 10nF 60 55 50 10k 500k 1.0M Oscillator Frequency, IOSC (Hz) http://www.hgsemi.com.cn 1.0nF 70 100pF 500pF 20k 50k 100k 200k 200pF 500k 1.0M Oscillator Frequency, IOSC (Hz) 4 2016 APR UC3844/3845 Current Sense Input Threshold vs. Error Amp Output Voltage 0 VCC = 15V VOUT = 2.0V ~ 4.0V RL = 100k TA = 25℃ 80 Gain 30 60 60 40 90 Phase 20 120 0 150 10 100 1.0k 10k 100k 1.0M 180 10M 1.2 1.0 TA = 125℃ 0.8 TA = 25℃ 0.6 0.4 TA = -55℃ 0.2 0 0 2.0 4.0 6.0 8.0 Error Amp Output Voltage, VOUT (V) Frequency, f (Hz) http://www.hgsemi.com.cn Supply Current, ICC (mA) 5 UCX844 TYPICAL CHARACTERISTICS(Cont.) Output Saturation Voltage, VO(SAT) (V) „ VCC = 15V UCX845 -20 Excess Phase Degrees, φ Open Loop Voltage Gain, GV (dB) 100 Current Sense Input Threshold, VIN(THR) (V) Error Amp Open Loop Gain Phase vs. Frequency 2016 APR