INTEGRATED CIRCUIT LOGIC FAMILY

1. INTEGRATED CIRCUIT LOGIC FAMILY ©2009, CE Department

2. Introduction • ICs have made digital systems more reliable by reducing the number of external interconnection from one device to another. • ICs have reduced the amount of electrical power needed to perform a given function. • IC cannot handle very large currents or voltages because the heat generated in such small spaces would cause temperature to rise beyond acceptable limits • ICs are principally used to perform low-power circuit operations that are commonly called information processing. ©2009, CE Department

3. Introduction • Rapidly growth from SSI, with fewer than 12 gates per chip; through MSI, with 12 to 99 equivalent gates per chip • Others – LSI, VLSI, ULSI and GSI • There are some things IC cannot do – when deal with very large current ©2009, CE Department

4. Digital IC Terminology • VIH (min) – High level input voltage. The minimum level required for a logical 1 at an input. Any voltage below this level will not be accepted as a HIGH by the logic circuit • VIL (max) – The maximum input voltage for logic zero • VOH (min) – The minimum voltage level at a logic circuit output in the logic 1 state under defined load conditions ©2009, CE Department

5. Digital IC Terminology (cont.) • VOL (max) – Low level output voltage. The maximum voltage level at a logic circuit output in the logical 0 state under defined load conditions • IIH – High level input current. The current that flows into an input when a specified high level voltage is applied to that input • IIL – Low level input current. The current that flows into an input when a specified low level voltage is applied to that input ©2009, CE Department

6. Digital IC Terminology (cont.) • IOH – High level output current • IOL – Low level output current ©2009, CE Department

7. Exercise • Describe the input and output logic for IC 7442 ©2009, CE Department

8. Fan out • Also known as loading factor • Defined as the maximum number of logic inputs that an output can drive reliably • A logic circuit that specify to have 10 fan out can drive 10 logic inputs ©2009, CE Department

9. Propagation delay • Two types of propagation delay – tPLH , delay time in going from logical 0 to 1; tPHL delay from 1 to 0 ©2009, CE Department

10. Noise Immunity

11. Noise Immunity (cont.) • The high state noise margin VNH is defined as VNH = VOH (min) – VIH (min) • The low state noise margin VNL is defined as VNL = VIL (max) – VOL (max) ©2009, CE Department

12. Power Requirements • Every IC need a certain power requirement to operate • This power supply is come from the voltage supply that connected to the pin on the chip labeled VCC(TTL) or VDD(MOS) • The amount of power require by ICs is determined by the current that it draws from the VCC • The actual power is ICCxVCC ©2009, CE Department

13. Cont. • ICC(avg) = (ICCH + ICCL)/2 • PD(avg) = ICC(avg)Xvcc ©2009, CE Department

14. The TTL Logic Family FIGURE 8-7 (a) Basic TTL NAND gate; (b) diode equivalent for Q1. ©2009, CE Department

15. TTL NOR gate ©2009, CE Department

16. TTL Data sheet • In 1964, Texas Instruments corporation introduced the first line of standard TTL ICs • The 54/74 series, most widely used IC logic families • The difference between 54 and 74 series is a range of temperatures • IC number is the same with all series produce by different manufactures • Each manufacturer however usually used the prefix that represent the special words – Texas Instrument uses the prefix SN, National semiconductor uses DM etc ©2009, CE Department

17. Supply Voltage and Temperature Range • 74ALS series and the 54ALS series use nominal supply voltage (VCC) of 5V, but can tolerate a supply variation of 4.5 to 5.5V. • 74ALS series can operate properly in ambient temperatures ranging from 0 to 70 degrees C, while the 54ALS series can handle -55 to +124 degree C. ©2009, CE Department

18. Voltage Levels • Input and output voltage levels can be found on the data sheet. • The min and max values shown are for worst case conditions of power supply, temperature and loading conditions

19. TTL Series Characteristics • We have found the type of ICs – 74, 74LS, 74ALS before • LS – low power Schottky, ALS – advance low power Schottky • The function is same, but the difference is on the characteristic

20. TTL Data Sheet

21. TTL Series Characteristics • 74 series of TTL – offers a wide variety of gates and flip flops • Consist of: a. Standard TTL, 74 series – no longer be use b. Schottky TTL, 74S series c. Low-power Schottky TTL, 74LS Series d. 74AS e. 74ALS and 74F ©2009, CE Department

22. Schottky TTL, 74S Series • 7400 series operates using saturated switching in which many of the transistors, when conducting will be in saturated condition • This can causes a storage time delay ts when the transistors switch from ON to OFF and effect the speed • 74S series come to solve the speed problem • It accomplishes this by using a Schottky barrier diode (SBD) ©2009, CE Department

23. Schottky TTL, 74S Series (cont.) ©2009, CE Department

24. Advances Schottky TTL, 74AS series • 74AS give more advance on speed switching of TTL ICs at much lower consumption • The comparison is shown in the following table for a NAND gate in each series ©2009, CE Department

25. Advanced Low Power Schottky TTL, 74ALS Series • Improved on both speed and power dissipation ©2009, CE Department

26. Example • Use table 8-6 to calculate the dc noise margins for a typical 74LS IC. How does this compare with the standard TTL noise margins ? Solution • 74LS VNH = VOH(min) – VIH(min) = 2.7 – 2.0 = 0.7 V ©2009, CE Department

27. TTL Loading and Fan Out ©2009, CE Department