Tips for PCB and Custom ASIC design

Tips for 2^nd version PCB

• Cut the power domain in high voltage and low voltage.
  
• Add cap filter for sharp clk edge from Arduino.
  
• Give the prototype larger space between components.
  
• LED for power indication.
  
• Push buttons. Momentum for switch and trigger for event like shift the shift register.
  
• Default push or pull resistor. Use surface mount resisters: small and optional since it may be pulled or pushed already.
  
• Put 1Ohm power resistors on and test lead across it to measure current.
  
• SMB and SMA has same footprint. SMA it is better in performance (20G v.s. 4G bandwidth) and the handling (SMB seems to be quite difficult to unplug, afraid of destroy the board).
  

 
 

Tips for PAD design: use Schmitt trigger to avoid noise in digital PADs.

 
 

Tips for shiftReg design:

1. Make all '0' a valid state for testing.
   
2. Add asynchronized
   reset to at least possibly set all shiftReg to all '0' state.
   

Tips for long shiftReg design

• Give clock in the last to the first order.
  
• Group the DFF, and add buffer for clocks between groups also use Last to First order. ??
  

 
 

Reminder: for robust testing process

• Always monitor the current.
  
• Current measure in DMM is not as robust as voltage measurement. Thus measure the voltage across a small resistor (e.g. 1 Ohm) is a good choice.
  
• So why not put a resister on PCB.  do it for 2^nd PCB. note for power rating.