Echelon FT 3150 Smart Transceiver - Manual (Page 140)

Appendix C - Design and Handling Guidelines
134 FT 3120 / FT 3150 Smart Transceiver Data Book
3. All low-impedance equipment (pulse generators, etc.) should be connected to CMOS inputs only after the device
is powered up. Similarly, this type of equipment should be disconnected before power is turned off.
4. A circuit board containing CMOS devices is merely an extension of the device and the same handling precautions
apply. Contacting connectors wired directly to devices can cause damage. Plastic wrapping should be avoided.
When external connections to a PC board address pins of CMOS integrated circuits, a resistor should be used in
series with the inputs or outputs. The limiting factor for the series resistor is the added delay caused by the time
constant formed by the series resistor and input capacitance. This resistor will help limit accidental damage if the
PC board is removed and is brought into contact with static-generating materials. For convenience, equations for
added propagation delay and rise-time effects due to series-resistance size are given in Figure C.6.
5. All CMOS devices should be stored or transported in materials that are antistatic. Devices must not be inserted
into conventional plastic “snow,” Styrofoam
®
, or plastic trays. Devices should be left in their original container
until ready for use.
6. All CMOS devices should be placed on a grounded bench surface and operators should ground themselves prior
to handling devices, since a worker can be statically charged with respect to the bench surface. Wrist straps in con-
tact with skin are strongly recommended. See Figure C.7.
7. Nylon or other static-generating materials should not come in contact with CMOS circuits.
8. If automatic handling is being used, high levels of static electricity may be generated by the movement of devices,
belts, or boards. Reduce static build-up by using ionized air blowers or room humidifiers. All parts of machines
which come into contact with the top, bottom, and sides of IC packages must be grounded metal or other conduc-
tive material.
9. Cold chambers using CO
2
for cooling should be equipped with baffles, and devices must be contained on or in
conductive material, or soldered onto a PCB.
10. When lead-straightening or hand-soldering is necessary, provide ground straps for the apparatus used and be sure
that soldering ties are grounded.
11. The following precautions are in reference only to FT-X1 transformers during wave-solder operations.
a. The solder pot and conductive conveyor system of the wave-soldering machine must be grounded to an earth
ground.
b. The loading and unloading work benches should have conductive tops which are grounded to an earth ground.
c. Operators must comply with precautions previously explained.
d. Completed assemblies should be placed in antistatic containers prior to being moved to subsequent stations.