1. The George Washington University School of Engineering and Applied Science Department of Electrical and Computer Engineering ECE122 – 30 Lab 2: CMOS Design Jason Woytowich September 9, 2005

2. Hierarchical Design Strategy Complex designs should be broken down into manageable pieces. CPU Bus Interface Execution Unit Register File Control Unit ALUFPU AdderShifterMultiplier

3. Hierarchical Design Strategy Proper breakdown of the circuit decreases the difficulty of your design and testing. Low level module implementations can be reused within the same design, or in other designs. Low level modules can be replaced with functionally equivalent implementations.

4. Lab activity – CMOS Buffer Build a CMOS buffer out of CMOS inverter modules. Test your design.

5. Gate Delay Gate Delay is the amount of time it takes a change of input to appear as a change on the output. Gate Delay is measured from the 50% point on the input signal to the 50% point on the output. Input Output tptp

6. Gate Delay We also characterize the transition time of a signal. In this case we use the 10% and 90% points. t pLH 10% 90% t pHL 10% 90%

7. Gate Delay The load capacitance severely affects the gate delay. Inv1 Inv2

8. Lab activity – Gate Delays Using a single inverter as a load, find the gate delays of your inverter and your buffer. Check 0->1 and 1->0 transitions. tptp

9. SCMOS Library Scalable CMOS Library Contains (just about) every digital logic component you need to build anything. And, Or, Xor, Nand, Nor, Xnor, Inv, Buf, Flip-flops, Pads, Capacitors, Resistors Each of these components has a specific layout mapped to it. It does not layout individual transistors.

10. Lab activity – Gate delays Compare the gate delays of the library buffer with yours. Be sure to use the same load or the measurements are meaningless.

11. Lab activity – Multiple inputs Create a single test-bench which tests all the possible inputs to either the Nand, Nor or Xor gates.

12. Voltage Transfer Characteristic Vin on the X-Axis and Vout on the Y-Axis Vin Vout 5V 0V 5V

13. Homework Using the ml2_125 model file, create an inverter so that it has a symmetric VTC. Adjust only Wn and Wp. Keep Ln,p constant. Use a 10pF load. Find the t pHL t pLH and t p for your inverter using the same inverter as a load. Vary the size from 1 to 100 times the width in increments of 10. Keep (Wn/Wp) constant.