Chapter 14:

1. Chapter 14: Integrated Circuit Applications

2. Introduction • Oscillators and phase locked loops are two important circuits widely used in electronics. • Integrated circuits are used throughout industry for complex circuits in small, cost-effective packages. • Some ICs perform digital functions, others perform analog functions. Still others perform both in the same package. Chapter 14 - Integrated Circuit Applications

3. Oscillator Circuits • Oscillator circuits require a dc power supply, generate an output waveform, but require no input signal. • Typically, they create a triangle, square, sine wave with no input other than the dc power. • There are many types of oscillator circuits and designs. Chapter 14 - Integrated Circuit Applications

4. Overview • In the circuit below, the frequency selective filter allows only one specific frequency, or range of frequencies to be fed back to the input of the amplifier. • This feedback begins a regenerative process that establishes the oscillator operation. Chapter 14 - Integrated Circuit Applications

5. Overview • The block diagram below illustrates another class of oscillator known as a relaxation oscillator. • A relaxation oscillator relies on the time delay of an RC circuit to determine the frequency of operation. Chapter 14 - Integrated Circuit Applications

6. Triangle Generator • In the relaxation oscillator below, U1, R1, and C1 are configured as an integrator. U2, R2, and R3 form a noninverting voltage comparator. • The triangle wave alternately triggers the voltage comparator, resulting in both triangular and square waves. Chapter 14 - Integrated Circuit Applications

7. Wien-Bridge Oscillator • A Wien-Bridge Oscillator is a classic circuit used to generate sine waves. • It uses a series RC and a parallel RC circuit in combination as the frequency selective circuit. • See following slide for example. Chapter 14 - Integrated Circuit Applications

8. Wien-Bridge Oscillator Chapter 14 - Integrated Circuit Applications

9. 555 Timer • The 555 integrated circuit has been around for more than two decades, but continues to be popular in electronic design. • It is a versatile device that can perform as a timer, time-delay circuit, oscillator, voltage-controlled oscillator, and many other functions. • See example on following slide. Chapter 14 - Integrated Circuit Applications

10. 555 Timer Chapter 14 - Integrated Circuit Applications

11. Crystal Oscillators • A crystal is a component that is constructed by placing a thin slice of quartz between two metal plates. • Crystals rely on the piezoelectric effect. The piezoelectric effect causes the crystal to produce a voltage when subjected to mechanical stress. • The piezoelectric effect also causes a crystal to vibrate at its naturally occurring mechanical frequency when subjected to an electric field. Chapter 14 - Integrated Circuit Applications

12. Crystal Oscillators • Crystals have very high values of “Q” and their impedance and phase characteristics vary abruptly on either side of resonance. • These properties make crystal oscillators very stable. • Frequency drift is primarily due to temperature variations. • See example of crystal oscillator on following slide. Chapter 14 - Integrated Circuit Applications

13. Crystal Oscillators Chapter 14 - Integrated Circuit Applications

14. CMOS Inverter Crystal Oscillator • A crystal can be used with a CMOS inverter to form an oscillator that produces a very stable square wave. Chapter 14 - Integrated Circuit Applications

15. Parasitic Oscillations • By design, oscillators include amplification, frequency selection, and positive feedback. • Many types of components in electronic circuits can inadvertently provide the requirements for oscillation even though the circuit is not intended to be an oscillator. This undesired oscillation is referred to as parasitic oscillation. Chapter 14 - Integrated Circuit Applications

16. Parasitic Oscillations • Routing of wiring and poor ground connections are the most common causes of parasitic oscillation. • Decoupling capacitors are used in circuits to remove unwanted high-frequency energy from the power distribution line. • If a decoupling capacitor becomes open, high-frequency oscillation can occur in a circuit. Chapter 14 - Integrated Circuit Applications

17. Phase-Locked Loops • Phase-locked loops (PLL) are often used in electronics as frequency generators. • The following slide shows a functional block diagram of a PLL. Chapter 14 - Integrated Circuit Applications

18. Phase-Locked Loops Chapter 14 - Integrated Circuit Applications

19. Representative Circuit • The diagram at the right is a Clock Synthesizer chip commonly used for microprocessor clocks. • It generates the following signals: • 16 synchronized clock signals at up to 66.66 MHz. • PCI clock at 33.3 MHz. • USB clock at 48 MHz. • I/O clock at 24 Mhz • This chip is based upon two PLLs. Chapter 14 - Integrated Circuit Applications

20. Industrial Computer Applications • Computers are used in industry for many purposes, including: • Monitoring manufacturing processes. • Controlling machines. • Inventory management. • Information processing. • This section looks at devices related to industrial applications and devices. Chapter 14 - Integrated Circuit Applications

21. A transducer is a device that converts one form of energy into another form of energy. The table below outlines common transducers: Transducers Chapter 14 - Integrated Circuit Applications

22. Instrumentation Amplifiers • The electrical output from a typical transducer is quite small and as they are frequently used in critical applications, special instrumentation amplifiers are used. • Factors affecting the need for instrumentation amplifiers are: • Small transducer output signals. • Distance between the sensor and computer may be great. • Harsh electrical environment Chapter 14 - Integrated Circuit Applications

23. Instrumentation Amplifiers • Instrumentation amplifiers are high-quality op amps that feature optimized characteristics: • Common-mode rejection ratio • Low dc offset voltages • Low output impedances • High input impedances • Stable gain characteristics Chapter 14 - Integrated Circuit Applications

24. Instrumentation Amplifiers • The following slide is an example of an instrumentation amplifier showing the external gain resistor and shielded inputs. Also shown is the equivalent circuit instrumentation amplifier used with a strain gage as its input. Chapter 14 - Integrated Circuit Applications

25. Instrumentation Amplifiers Chapter 14 - Integrated Circuit Applications

26. V/F and F/V Conversion • Two complementary circuit functions widely used in industrial electronics are: • Voltage-to-frequency conversion • Frequency-to-voltage conversion. • One common use of these circuits is to provide a convenient way to transmit transducer information over long distances in harsh environments. Chapter 14 - Integrated Circuit Applications

27. Voltage-to-Frequency Conversion • Several techniques are available to construct a circuit whose output frequency is proportional to its input voltage. • One popular integrated circuit is the VFC32, which incorporates a voltage controlled oscillator as an integral part of a phase locked loop. • See example on following slide. Chapter 14 - Integrated Circuit Applications

28. Voltage-to-Frequency Conversion Chapter 14 - Integrated Circuit Applications

29. Frequency-to-Voltage Conversion • In F/V conversion, the circuit provides a dc output that is proportional to the applied frequency. • The VFC32 discussed earlier can be configured to perform frequency-to-voltage conversions as shown on the following slide. Chapter 14 - Integrated Circuit Applications

30. Frequency-to-Voltage Conversion Chapter 14 - Integrated Circuit Applications

31. Troubleshooting Circuits Based on ICs • Because of the number of IC devices available, detailed instructions on how to troubleshoot every specific IC is impractical. • There are general techniques for troubleshooting oscillator circuits and some other types of ICs. Chapter 14 - Integrated Circuit Applications

32. Troubleshooting Oscillator Circuits • Problems with oscillator circuits generally fall into one of the following categories: • Completely inoperative (no output signal). • Distorted output waveform. • Incorrect or unstable frequency of oscillations. • Things to check on an oscillator circuit: • DC supply voltages. • Shift in dc operating point. • Check components responsible for frequency determination. Chapter 14 - Integrated Circuit Applications

33. Troubleshooting Other IC-based Systems • Integrated circuits can be assigned to two general categories: • Those with internal memory and • Those with no internal memory. • Devices with internal memory may be programmable and therefore outputs are difficult to evaluate using normal techniques. • The outputs of devices with no internal memory are easier to troubleshoot with conventional techniques. Chapter 14 - Integrated Circuit Applications