Penn ESE370 Fall DeHon 1 ESE370: Circuit-Level Modeling, Design, and Optimization for Digital Systems Day 22: October 22, 2014 Pass Transistor Logic

Teaser What does this do? Penn ESE370 Fall DeHon 2

Previously Penn ESE370 Fall DeHon 3

Impact of Capacitance Penn ESE370 Fall DeHon 4

Today Pass Transistor Circuits C diff >0 Penn ESE370 Fall DeHon 5

Pass Transistor Penn ESE370 Fall DeHon 6

Identify Function What function? Penn ESE370 Fall DeHon 7

Area Compare with CMOS circuit? Penn ESE370 Fall DeHon 8

Output What is Vout if A=0, B=0? Penn ESE370 Fall DeHon 9

Output What is Vout if A=1, B=0, notB=1? Penn ESE370 Fall DeHon 10

Output Is this a restoring gate? Penn ESE370 Fall DeHon 11

Output What does output look like (DC transfer)? –(B=1, notB=0, sweep A, notA=CMOS inv(A)) Penn ESE370 Fall DeHon 12

Pass TR transfer (B=1) Penn ESE370 Fall DeHon 13

CMOS Inverter Transfer Penn ESE370 Fall DeHon 14

Reasonable Input to CMOS Inverter? Penn ESE370 Fall DeHon 15

Pass tr xor2 with inv restore Penn ESE370 Fall DeHon 16

Compare CMOS Is this a fair comparison? Penn ESE370 Fall DeHon 17

Required to use? What need to add to make substitutable with CMOS? Penn ESE370 Fall DeHon 18

Restore Output Penn ESE370 Fall DeHon 19

Restore Output Area? (compare to CMOS) Penn ESE370 Fall DeHon 20

Chain Together Penn ESE370 Fall DeHon 21

Analyze Stage Penn ESE370 Fall DeHon 22

Analyze Stage What’s different about this? Penn ESE370 Fall DeHon 23

Delay B=0, C diff =0? Penn ESE370 Fall DeHon 24

Equivalent RC Circuit Penn ESE370 Fall DeHon 25

Circuit Penn ESE370 Fall DeHon 26

Delay B=1, C diff =0? Penn ESE370 Fall DeHon 27

Equivalent RC Circuit Penn ESE370 Fall DeHon 28

Circuit Penn ESE370 Fall DeHon 29

Circuit What’s different about this? Penn ESE370 Fall DeHon 30

C diff >0 Penn ESE370 Fall DeHon 31

Contact/Diffusion Capacitance C j – diffusion depletion C jsw – sidewall capacitance L S – length of diffusion Penn ESE370 Fall DeHon 32 LSLS

Impact of Capacitance Penn ESE370 Fall DeHon 33

Inverter Delay Delay driving another inverter? –Include Cdiff=  Cgate Penn ESE370 Fall DeHon 34 W=1

Delay B=1, C diff =  C g ? Penn ESE370 Fall DeHon 35

Equivalent RC Circuit? Penn ESE370 Fall DeHon 36

Equivalent RC Circuit Penn ESE370 Fall DeHon 37

Bonus (time permit) What does this do? Penn ESE370 Fall DeHon 38 A B More examples in book.

Idea There are other circuit disciplines Can use pass transistors for logic –Sometimes gives area or delay win Penn ESE370 Fall DeHon 39

Admin Project –Hopefully done with baseline –Ron office hours today –Get started on design-space exploration and optimization Penn ESE370 Fall DeHon 40