AZ3844

Advanced Analog Circuits Data Sheet AZ3842/3/4/5 Features · Robust VREF Line/Load Regulation Low Line Regulation : 4mV Low Load Regulation : 4mV High Stability of Reference Voltage over a Full Temperature Range: 0.2mV/ oC Operating Frequency up to 500KHz High PWM Frequency Stability over a Full Temperature Range: 2.5% High PWM Frequency Stability under a Full Supply Voltage Range: 0.2% Accurate Over-temperature Protection with Hysteresis UVLO with Hysteresis CURRENT MODE PWM CONTROLLER General Description The AZ3842/3/4/5 are high performance fixed frequency current-mode PWM controller series. These integrated circuits are optimized for off-line and DC-DC converter applications with minimum external components. They feature under-voltage lockout (UVLO) circuit for low start-up current, trimmed oscillator for precise duty cycle control, current sense comparator providing maximum current limiting and a totem pole output stage for increasing output current. In addition, these ICs also feature accurate protection against over-temperature, over-current and maximal output power. The AZ3842 and AZ3844 have UVLO thresholds of 15.5V(on) and 10V(off); The corresponding thresholds for AZ3843 and AZ3845 are 8.4 V(on) and 7.8V(off). The AZ3842 and AZ3843 can operate approaching 100% duty cycle; AZ3844 and AZ3845 can operate from zero to 50% duty cycle. These ICs are available in 3 packages: SOIC-8, DIP-8 and SOIC-14. · · · · · · Applications · · · · · · Off-line Converter DC-DC Converter Voltage Adapter CRT Monitor Power Supply Desktop Power Supply DVD/STB Power Supply SOIC-8 DIP-8 SOIC-14 Figure 1. Package Types of AZ3842/3/4/5 March 2003 1 Rev: 1.0 Advanced Analog Circuits Data Sheet AZ3842/3/4/5 M Package (SOIC-14) COMP 1 2 3 4 5 6 7 14 13 12 11 10 9 8 VREF N/C VCC PWR VC OUTPUT GND PWR GND CURRENT MODE PWM CONTROLLER Pin Configuration P/M Package (DIP-8/SOIC-8) COMP VFB ISENSE RT/CT 1 2 3 4 8 7 6 5 VREF VCC OUTPUT GND N/C VFB N/C ISENSE N/C RT/CT Figure 2. Pin Configuration of AZ3842/3/4/5 (Top View) Pin Description Pin Number 8-pin 1 2 3 4 14-pin 1 3 5 7 Pin Name COMP VFB ISENSE RT/CT Function This pin is the Error Amplifier output and is made available for loop compensation. 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. 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. The positive supply of the control IC. This is the reference output. It provides charging current for capacitor CT through resistor RT. This pin is a separate power ground return that is connected back to the power source. It is used to reduce the effects of switching transient noise on the control circuitry. The Output high state (VOH) is set by the voltage applied to this pin. With a separate power source connection, it can reduce the effects of switching transient noise on the control circuitry. This pin is the control circuitry ground return and is connected back to the power source ground. No connection. These pins are not internally connected. 5 6 7 8 10 12 14 8 11 GND OUTPUT VCC VREF PWR GND PWR VC 9 2,4,6,13 GND N/C March 2003 2 Rev: 1.0 Advanced Analog Circuits Data Sheet AZ3842/3/4/5 CURRENT MODE PWM CONTROLLER Functional Block Diagram VCC GND 7(12) 34V 5(9) UVLO S/R 5V REF 7(11) VCC (PWR VC) VREF 8(14) INTERNAL BIAS 2.50V VREF GOOD LOGIC RT/CT 4(7) OSC T (Note) 6(10) OUTPUT GND (PWR GND) A(B) A for 8-pin B for 14-pin OVER TEMP PROTECT ERROR AMP 2(3) 1(1) 3(5) R 1V 2R 5(8) S R CURRENT SENSE COMPARATOR PWN LATCH Note: Toggle flip-flop used for 3844/45 only VFB COMP ISENSE Figure 3. Functional Block Diagram of AZ3842/3/4/5 Ordering Information Package SOIC-8 DIP-8 SOIC-14 Temperature Range Part Number AZ3842/3/4/5M AZ3842/3/4/5P AZ3842/3/4/5MM Marking ID 3842/3/4/5M AZ3842/3/4/5P AZ3842/3/4/5MM Packing Type Tape/Reel/Tube Tube Tape/Reel -40oC~85oC March 2003 3 Rev: 1.0 Advanced Analog Circuits Data Sheet AZ3842/3/4/5 CURRENT MODE PWM CONTROLLER Absolute Maximum Ratings (Note 1, 2) Parameter Supply Voltage Output Current Analog Inputs (8-pin: pin2,3, 14-pin: pin3,5) Error Amp Output Sink Current Power Dissipation at TA< 25 oC (DIP-8) Power Dissipation at TA