1. Adapter Board Design Changes
Jeremy Sandoval
7/14/14

2. Outline 1. Analyzing FEI4 Adapter Card 1.1a
2. T3MAPS Adapter Card vs. FEI4 Adapter Card 1.1a
3. Goals for T3MAPS Adapter Board v3
4. High-Speed Digital Design Techniques
5. High-Speed Digital Design Techniques cont.
6. High-Speed Digital Design Techniques cont.
7. Plan for the Week
8. References

3. Analyzing FEI4 Adapter Card 1.1a
Studied the layout of FEI4 Adapter Card Rev1.1a to learn more about successful high-speed design:
T3MAPS Adapter Boards v2
FEI4 Adapter Card 1.1a
Uses SN74AVC8TPWR Level Shifter
Uses SN74AVC4TPWR Level Shifters
2 Layers
4 Layers
Operates up to 30Mhz
Operates up to 40Mhz
Board to Board Connector
High speed traces routed anti-parallel
High speed traces routed in parallel
Level shifter I/Os placed close to connectors

4. Side-by-Side Layout Comparison
T3MAPS Adapter (left)
Red = top layer
Blue = bottom layer
FEI4 Adapter (right)
Green = top layer

5. Goals for T3MAPS Adapter Board v3
Improve design to achieve higher operating speeds (>30MHz up to possibly 90MHz)
Change output pins (going to T3MAPS) to a polarized ribbon cable connector
Avoid noise on the ground plane
Shorten high speed traces between connectors as much as possible
Remove parallel terminating resistors, keep series resistors
4 layer stack up
Add additional bypass capacitors
Keep terminating series resistor close to level shifter I/Os

6. High Speed Design Techniques
Pay attention to high frequency current paths on the board and avoid breaks in ground plane:
[1] TI’s High Speed PCB Layout Techniques

7. High Speed Design Techniques cont.
Bypass Capacitors are affected by frequency
The material is a major factor in the characteristics of the capacitor over temperature and frequency
The most pronounced elements are the true capacitance, the equivalent series resistance (ESR), and the equivalent series inductance (ESL)
ESL causes the capacitor to stop behaving like a true capacitor at high frequencies as the impedance starts to increase rather than keep decreasing
Ceramic capacitors are most widely used bypass capacitor
Several grades to choose from with COG being the best and Y5V the worst
For example, Y5V capacitance can vary as much as +22% over temperature and frequency whereas COG can vary less than 0.1% at 10Mhz
[1] TI’s High Speed PCB Layout Techniques

8. High Speed Design Techniques cont.
[1] TI’s High Speed PCB Layout Techniques

9. Plan for this week
Finish board layouts for T3MAPS adapter and circulate (By Tuesday)
Run circuit simulations in Altium Designer
Take lab inventory and compile bill of materials
Lab hours: Wed: Fri: I can be in the lab More if needed, just send me an

10. References
[1] TI’s High Speed PCB Layout Techniques,