Digital Circuits. Innovation Fellows Program

Transcription

1 Innovation Fellows Program Digital Circuits, Department of Biomedical Engineering, University of Minnesota

2 Topics Digital Electronics TTL and CMOS Logic National Instrument s Multisim (SPICE) and Ultiboard Software Prototyping with Breadboards Boolean Logic CMOS and TTL IC Packaging and Pinouts Various Devices and Circuits Schmitt triggers Contact debouncing Simulation and elimination of noise; voltage summing Leading edge detection Counters and 7-segment display Drivers for LEDs, lamps and relays Ad and DA Converters

3 Dawn of the Digital Age Slide Rule - 17 th Century to ~ Home Computer 1969 (Steven Saliterman) Intel 8080 Microprocessor 1974 Altair First Commercial Personal Computer 1975 (Ed Roberts)

4 Microelectronics Revolution Triode tube 1915 (Langmuir) Point-contact transistor 1947, Bell Labs (Brattain and Bardeen). Junction transistor 1948 (Shockley), IC 1958 (Kibly and Noyce), & Intel Pentium Microprocessor 10 8 Transistors!

5 From Molten Silicon to IC Chips Molten silicon - Czochralski puller technique Silicon wafer diced into integrated circuits (DIP and SMD). Single crystal silicon boule

6 Digital Logic IC Families TTL - Transistor-Transistor Logic Versions Standard, high speed, low power and Schottky - e.g. 74LS00 series ECL - Emitter Coupled Logic CMOS - Complementary Metal Oxide Semiconductor Logic e.g. 4000B and 74HC00 series.

7 TTL Logic Positive logic 1 is positive (high) and 0 is ground or below 0.8 volt (low). The outputs can directly drive up to ten other TTL logic inputs (fanout of ten). However, only one input is allowed (fan-in of one). Buffers have a fan-out of ~30. 5 VDC power supply typical. Unconnected inputs tend to pull themselves up to a positive value. Current sinking logic. The output-low state is capable of sinking 16 ma. The output-high state is above 2.4 volts, typically around 3.3 volts below the supply voltage. Require a despiking capacitor (0.1 to.01µf) every 1 to 4 ICs (if separated by no more than 3 ) to eliminate spikes caused by internal transistor switching.

8 CMOS Logic Low cost. Inputs are open circuits and easy to drive. Almost no power supply current needed except during input logic changes. Logic changes half-way up the power supply voltage, giving good noise immunity (at least better than TTL). Wide range of power supply voltages, from 3 to 15 Vdc The unloaded output logic swings the full range of the power supply. CMOS circuits create little noise of their own. CMOS circuits pass along less noise.

9 Design with NI Multisim

10 CMOS Packages & Pins Lancaster, D. and Berlin, H.M. CMOS Cookbook. H.W. Sams, Indianapolis, IN (1988)

11 Inverter 74HC04 Notice the output is inverse to the input. Input High Low Output Low High

12 Available Logic Gates in the 74HC04 Lancaster, D. and Berlin, H.M. CMOS Cookbook. H.W. Sams, Indianapolis, IN (1988)

13 NAND 74HC00 Input 1 Input 2 Output If either or both inputs are low the output will be high.

14 Available Logic Gates in the 74HC00 In addition to this NAND gate, there are many different types and combinations of Boolean logic gates to select from. These include AND, OR, NOR, Exclusive OR & NOR and others. Lancaster, D. and Berlin, H.M. CMOS Cookbook. H.W. Sams, Indianapolis, IN (1988)

15 Flip-Flop 74HC74 QQ QQ Notice the divide by 2 of frequency. The information presented to the D input goes on to the QQ output whenever the clock input changes from a low to a high level. If D is high, on clocking, QQ goes high and QQ goes low. If D is low, on clocking, QQ goes low and QQ goes high.

16 4 Bit Binary Counter with Buffer Drivers Place 2 3 =8 2 2 =4 2 1 =2 2 0 =1

17 Available Logic Gates in the 74HC74 In addition to this D-Flip-Flop, there are also JK Flip-Flops Lancaster, D. and Berlin, H.M. CMOS Cookbook. H.W. Sams, Indianapolis, IN (1988)

18 Counter on Breadboard

19 Tri-State Logic 74HC126

20 Available Logic Gates in the 74HC126 Lancaster, D. and Berlin, H.M. CMOS Cookbook. H.W. Sams, Indianapolis, IN (1988)

21 Schmitt Trigger 74C14

22 Switch Contact Noise Thresholds are ~ 1.35 V for Low and 3.15 V for High Mechanical contact noise can cause multiple pulses to occur the first 100 µs or so. In this example, three pulses would be generated.

23 Contact Debouncer Schmitt Trigger Output Input Switch Off & On

24 Creating Noise with Voltage Summing Voltage Summing Voltage Inverter

25 Noise Eliminator Schmitt Trigger 4093B Summer Input Output Voltage Follower

26 Leading Edge Detector Schmitt Trigger Debounced button pushes Single pulse with each positive edge

27 Available Logic Gates in the 74HC14 & 4093B Lancaster, D. and Berlin, H.M. CMOS Cookbook. H.W. Sams, Indianapolis, IN (1988)

28 One-and-only One Synchronized Pulse Clock Button Output is a synchronized pulse with the clock, while the button push is not.

29 Driving LEDs 4049B Current sourcing. Current sinking. RR 1 oooo 2 = VV FF II FF The 4049 Inverter- Buffer can source or sink sufficient current to light the LED directly. For other CMOS logic you need to have a transistor. Push Button Debounce Certain devices, like counters, may have built in LED drivers.

30 Available Logic Gates in the 4049B Lancaster, D. and Berlin, H.M. CMOS Cookbook. H.W. Sams, Indianapolis, IN (1988)

31 Decade Stepper 4017B

32 Available Logic Gates in the 4017B In addition to this divide-by -10 counter, there are many other types, some with multiple stages; different bases decade, binary, and octal; directions - up-down; and ripple vs. synchronous. Lancaster, D. and Berlin, H.M. CMOS Cookbook. H.W. Sams, Indianapolis, IN (1988)

33 Decade Counter 4518B & 4511B A 7-segment common cathode display: Display current limiting resistors 7-segment latch & drivers Dual synchronous divide by ten counter

34 Available Logic Gates in the 4518B & 4511B Lancaster, D. and Berlin, H.M. CMOS Cookbook. H.W. Sams, Indianapolis, IN (1988)

35 Lamp Driver with Transistor Lamp is rated 5 V and power of 200 mw. Required current: PPPPPPPPPP WW = II 2 RR = VVVV II = PPPPPPPPPP WW 200 mmmm = = 40 mmmm VV The 2N2222 is a general purpose medium power amplifier and switch, for I C of up to 500 ma (max. 1 A). 5

36 MOSFET Relay Driver with Transient Suppression MOSFET is a transconductance device (base current is negligible, base voltage controls collector current). The MOSFET allows for higher collector current than the BJT.

37 Analog to Digital Converters Analog to Digital Converters (ADC) Convert an analog signal such as voltage, into a digital signal. Resolution is the number of discrete values the converter can produce over the range of the analog signal. For example, an 8-bit encoder can decode an analog value to 2 8, or 256 different values. Sampling rate is subject to the Nyquist-Shannon sampling theorem. In simple terms, you must sample minimally at a rate twice that of the frequency in order to reproduce the original analog signal.

38 Digital to Analog Converters Digital to Analog Converters (DAC) Convert digital data into an analog signal, such as voltage or current. Commonly used to reproduce music from CD to amplifiers, speakers and headphones. The Arduino pins can be configured for ADC and DAC. Dedicated ADC/DAC chips are available from a number of manufacturers.

39 Summary Digital Electronics TTL and CMOS Logic Designing with NI Multisim (SPICE) and Ultiboard Software Prototyping with Breadboards Boolean Logic CMOS and TTL IC Packaging and Pinouts Various Devices and Circuits Schmitt triggers Contact debouncing Simulation and elimination of noise; voltage summing Leading edge detection Counters and 7-segment display Drivers for LEDs, lamps and relays AD and DA Converters