Schottky Ttl 1970s Package and Interconnect Schottky Ttl Boards

# Schottky TTL (early 1970s): Step 16 — Package and Interconnect Schottky TTL Boards

Package and Interconnect Schottky TTL Boards. Unlike ECL, which often demanded controlled-impedance transmission-line interconnect even for moderate trace lengths (ECL Step 12), Schottky TTL's packaging and board design stayed close to standard TTL practice specifically because that compatibility was the whole point of the family.

## 1. Packaging Stayed Conventional, by Design
Unlike ECL, which often demanded controlled-impedance transmission-line interconnect even for moderate trace lengths (ECL Step 12), Schottky TTL's packaging and board design stayed close to standard TTL practice specifically because that compatibility was the whole point of the family. Standard dual-in-line packages (DIPs), the same 14- and 16-pin footprints used for standard TTL, and ordinary (non-controlled-impedance) printed-circuit traces remained adequate for the large majority of 74LS designs, since 74LS's propagation delay was comparable to standard TTL's and its edge rates, while faster than standard TTL's in absolute terms, did not generally require transmission-line treatment at typical 1970s-1980s board trace lengths.

## 2. Real Diagram: Schottky TTL Board Layout Considerations by Family

Board Layout Discipline Required, by Logic Family ordinary trace routing sufficient vs. controlled-impedance treatment needed family decoupling need trace treatment std. TTL standard bulk caps ordinary traces 74LS local decoupling ordinary traces 74S careful local decoupling length limits on critical nets ECL (ref.) extensive, close-in controlled impedance required Schottky TTL sits between standard TTL and ECL on required layout discipline, closer to standard TTL

## 3. Where 74S Did Demand More Care
74S's faster edges, as Step 13 and Step 14 established, did push board designers toward more deliberate decoupling capacitor placement and length limits on the fastest, most timing-critical nets, especially clock distribution and wide simultaneously-switching buses, even though full controlled-impedance transmission-line design (vias, matched termination, careful stripline geometry) remained unnecessary for the great majority of 74S usage. This moderate, rather than extreme, interconnect discipline was itself part of Schottky TTL's commercial appeal: real speed gains without requiring the specialized board-design expertise ECL demanded.

## 4. Companion Diagram: Stage Sequence and Trend Summary

Schottky TTL (early 1970s): Step 16 stage sequence and schematic outcome trend for this step Packaging Stayed Conv… 1 Schottky TTL Board La… 2 Where 74S Did Demand … 3 Companion Diagram 4 sequence progression outcome trend (schematic) companion diagram: stage sequence and schematic trend for this step

## Package and Interconnect Schottky TTL Boards's Place in the Process Lineage
This is step 16 of 20 in the Schottky TTL (early 1970s) series, covering the packaging and interconnect practices that kept Schottky TTL compatible with standard TTL board design conventions.

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