Transcript chapter1
dce 2009 INTEGRATED CIRCUIT LOGIC FAMILY BK TP.HCM ©2009, CE Department dce 2009 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 2 dce 2009 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 3 dce 2009 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 4 dce 2009 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 5 dce 2009 Digital IC Terminology (cont.) • IOH – High level output current • IOL – Low level output current ©2009, CE Department 6 dce 2009 Exercise • Describe the input and output logic for IC 7442 ©2009, CE Department 7 dce 2009 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 8 dce 2009 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 9 dce 2009 Noise Immunity 10 dce 2009 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 11 dce 2009 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 12 dce 2009 Cont. • ICC(avg) = (ICCH + ICCL)/2 • PD(avg) = ICC(avg)Xvcc ©2009, CE Department 13 dce 2009 The TTL Logic Family FIGURE 8-7 (a) Basic TTL NAND gate; (b) diode equivalent for Q1. ©2009, CE Department 14 dce 2009 TTL NOR gate ©2009, CE Department 15 dce 2009 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 16 dce 2009 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 17 dce 2009 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 18 dce 2009 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 19 dce 2009 TTL Data Sheet 20 dce 2009 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 21 dce 2009 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 22 dce 2009 Schottky TTL, 74S Series (cont.) ©2009, CE Department 23 dce 2009 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 Propagation delay Power dissipation Speed-power product 74S 74AS 3ns 20 mW 60 pJ 1.7ns 8 mW 13.6 pJ ©2009, CE Department 24 dce 2009 Advanced Low Power Schottky TTL, 74ALS Series • Improved on both speed and power dissipation 74S Propagation delay Power dissipation Speed-power product 74AS 9.5 4 ns ns 1.2 mW 2 mW 4.8 pJ 19 pJ ©2009, CE Department 25 dce 2009 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 26 dce 2009 TTL Loading and Fan Out ©2009, CE Department 27