1. I/O STANDARDS & DESIGN Muthukumar Nagarajan 02/29/08

2. 2 IO Standards & Design AGENDA GOAL SIGNALING STANDARDS INPUT BUFFER OUTPUT BUFFER I/O DESIGNS ESD

3. 3 IO Standards & Design GOAL A peek into the world of I/O standards and I/O buffer design Brief Introduction to Signaling (I/O) Standards Key I/O parameters I/O buffer designs Analog design in I/O buffers

4. 4 IO Standards & Design I/O STANDARDS WHY I/O STANDARDS To create a common language that IC’s can use to communicate with each other and form a system to enable a solution I/O STD ORG’s Several governing bodies create communication protocols. The Electrical signaling standards (I/O std.) is one part of this protocol Some well known organizations JEDEC (LVTTL, LVCMOS, HSTL, SSTL) TIA/EIA (LVDS, VoIP) IEEE (802 LAN/MAN)

5. 5 IO Standards & Design I/O STANDARDS

6. 6 IO Standards & Design I/O BUFFER TYPE SINGLE ENDED A signal (Data or Clock) that is defined by a single port/wire/net Signal swing is Rail-to-Rail or a small swing around a fixed reference level DIFFERENTIAL A signal (Data or Clock) that is defined by the difference of two signals around a common mode level Small signal swings, High speed, Low noise

7. 7 IO Standards & Design INPUT BUFFER SINGLE ENDED (CMOS) Basically an inverter Designed for a specific Voltage Trip Point by simply using P vs. N FET W/L ratio DIFFERENTIAL Basically a Diff. Amp. Designed for a specific CM level and Input Swing FEATURES Hysterisis to improve Noise Immunity Input pin ESD Protection Buffer output to drive the Chip core Performance requirements (High speed, Low power, Low leakage, HV tolerance etc.) dictate buffer design and complexity

8. 8 IO Standards & Design INPUT BUFFER: TOPOLOGIES 1

9. 9 IO Standards & Design INPUT BUFFER: TOPOLOGIES 2

10. 10 IO Standards & Design INPUT BUFFER: TOPOLOGIES 3

11. 11 IO Standards & Design INPUT BUFFER : KEY PARAMETERS 1 VIH – Input HIGH Level VIL – Input LOW Level VHYST – Hysterisis (VIH - VIL) VREF – Input Reference Voltage VIPP – Peak-to-Peak Input Swing VICM – Input Common Mode Level FMAX – Max Frequency of operation ISB – Leakage Power ICC – Dynamic (Active) Power

12. 12 IO Standards & Design INPUT BUFFER : KEY PARAMETERS 2

13. 13 IO Standards & Design OUTPUT BUFFER SINGLE ENDED (CMOS) Basically an inverter Designed to drive large loads (several pF) DIFFERENTIAL Basically a Diff. Amp. Designed for a specific CM level and Output Swing FEATURES Tri-State Output pin ESD protection Programmable Drive strength, Slew rate Hot Swap, HV Tolerance Weak Pull-up, Pull-down Signal voltage domain converter Impedance Matching

14. 14 IO Standards & Design OUTPUT BUFFER: TOPOLOGIES 1

15. 15 IO Standards & Design OUTPUT BUFFER: TOPOLOGIES 2

16. 16 IO Standards & Design OUTPUT BUFFER : KEY PARAMETERS 1 VOH – Output HIGH Level @ IOH VOL – Output LOW Level @ IOL IOH – Output HIGH current @ VOH IOL - Output LOW current @ VOL IOZ – Output pin leakage tOR, tOF – Output Rise/Fall time Noise (On chip Pwr/Gnd and Signal) VOPP – Peak-to-Peak Output Swing VOCM – Output Common Mode Level FMAX – Max Frequency of operation ISB – Leakage Power ICC – Dynamic (Active) Power

17. 17 IO Standards & Design OUTPUT BUFFER : KEY PARAMETERS 2

18. 18 IO Standards & Design CY I/O DESIGN Programmable I/O’s in PSoC I/O Ring

19. 19 IO Standards & Design ESD