MC34067DWR2G

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1. Describe

The MC34067DWR2G/MC33067 are high performance zero voltage switch resonant mode controllers designed for off−line and dc−to−dc converter applications that utilize frequency modulated constant off−time or constant deadtime control. These integrated circuits feature a variable frequency oscillator, a precise retriggerable one−shot timer, temperature compensated reference, high gain wide bandwidth error amplifier, steering flip−flop, and dual high current totem pole outputs ideally suited for driving power MOSFETs. Also included are protective features consisting of a high speed fault comparator and latch, programmable soft−start circuitry, input undervoltage lockout with selectable thresholds, and reference undervoltage lockout. These devices are available in dual−in−line and surface mount packages.

2. Features

    1. Zero Voltage Switch Resonant Mode Operation

    2. Variable Frequency Oscillator with a Control Range Exceeding 1000:1

    3. Precision One−Shot Timer for Controlled Off−Time

    4. Internally Trimmed Bandgap Reference

    5. 4.0 MHz Error Amplifier

    6. Dual High Current Totem Pole Outputs

    7. Selectable Undervoltage Lockout Thresholds with Hysteresis

    8. Enable Input

    9. Programmable Soft−Start Circuitry

  10. Low Startup Current for Off−Line Operation

  11. NCV Prefix for Automotive and Other Applications Requiring Unique Site and Control Change Requirements; AEC−Q100 Qualified and PPAP Capable

  12. These Devices are Pb−Free, Halogen Free/BFR Free and are RoHS Compliant

3. PIN CONNECTIONS

4. Function Description

    1. introduce

As power supply designers have been working hard to increase power Conversion efficiency and reducing the size of passive components, The high frequency resonance mode power converter has Become an attractive alternative to tradition Pulse width modulation control. When compared to Pulse width modulation converter, resonant mode control Provides multiple benefits, including lower switching losses, Higher efficiency, lower EMI radiation and smaller size. A new integrated circuit has been developed to support this Power design trends. MC34067 resonator The mode controller is a high-performance bipolar IC dedicated Variable frequency power control of different frequencies More than 1.0 MHz. Integrated circuit provision Features and performance dedicated to zero voltage Switching resonant mode power supply application. The main purpose of the control chip is to provide a Fixed off-time to the gate of the external power MOSFET The repetition rate adjusted by the feedback control loop. The additional functions of the IC ensure system startup and Manage fault conditions in a safe and controlled manner. The simplified block diagram of the IC is shown on the front Page to identify the main functional blocks and Block-to-block interconnection. Various functions can be divided into two categories part. The first part includes the main path Generate the precise output pulses required frequency. This section includes variable frequencies Oscillator, one One-Shot, one pulse steering trigger, one pair Power MOSFET driver and wide bandwidth error Amplifier. The second part provides several peripherals Supported functions include voltage reference, Undervoltage lockout, soft start circuit and fault detector.

    2. Main path

Output pulse width and repetition rate adjustment Through the interaction of the variable frequency oscillator, One-time timer and error amplifier. Oscillator trigger One-Shot generates alternating pulses Turn into a pair of totem pole output drivers by flipping the switch trigger. Error amplifier monitor output The regulator also modulates the frequency of the oscillator. High-speed Schottky logic is used throughout the primary Control channels to minimize delay and increase high Frequency characteristics.

    3. Oscillator

Features of variable frequency oscillator Essential to the performance of high-precision controllers working frequency. In addition to triggering One-time timer and start output dead time, The oscillator also determines the initial voltage of a single flip-flop Capacitor. The oscillator is designed for The frequency exceeds 1.0 MHz. The error amplifier can Control the oscillator frequency at a frequency of 1000:1 Range, minimum and maximum frequency are both Through the right choice External components. The oscillator capacitor (COSC) is initially charged by transistor Q1. When COSC exceeds 4.9 V upper threshold of the oscillator comparator, base Q1 is pulled low, allowing COSC to pass External resistance (ROSC) and oscillator control current, (IOSC). When the voltage on the COSC is lower than 3.6 V The lower threshold of the comparator, Q1 turns on first and then turns on Charge COSC. The COSC charges from 3.6 V to 5.1 V in less than 50 ns. this COSC's high slew rate and propagation delay It is difficult for the comparator to control the peak voltage. this Overcome accuracy problems by clamping the bottom of Q1 Through the diode to the voltage reference. The peak voltage is Therefore, the oscillator waveform is accurately set to 5.1 V.

5. PACKAGE DIMENSIONS