v0-4 hardware build notes
1 July 2006

A few comments on the USB PCB

1. All surface mount Rs and Cs apart from the 1Mohm (r3), 4.7nF (C14) and tantalums are now 0805.

2. The 1Mohm and 4.7nF are safety components - the shield on the type B connector is floating

3. The 68013 device had an errata that stated that for bus powered operation a simple RC
reset circuit was incorrect and a decent power management (reset) chip was needed. This
is provided for on the PCB (U3). However, the 68013A claims that it is now OK to use an RC
reset circuit so as an alternative - do not fit both - you can use a 1uF cap (C15) and 27K
resistor (R5).

4. The board will take EITHER the 68013 OR the 68013A. The only difference is that the 24 MHz
xtal is supposed to be 12pF resonant for the A series device, but application notes on 
the cypress website suggest that 18pF works well for either

5. Do not fit JP1 - you only need this is you make a mess of programming the chip. You may also 
omit R1 if you wish by the same logic.

6. The PCB is a couple of millimetres smaller than the ExpressPCB board (v0-3)

7. The PCB is lead free but solders just fine with tin/lead solder

Dave



