1999 May 25 7
NXP Semiconductors Product data sheet
Quadruple ESD transient voltage
suppressor
BZA456A
Device placement and printed-circuit board layout
Circuit board layout is of extreme importance in the
suppression of transients. The clamping voltage of the
BZA456A is determined by the peak transient current and
the rate of rise of that current (di/dt). Since parasitic
inductances can further add to the clamping voltage
(V
= L di/dt) the series conductor lengths on the
printed-circuit board should be kept to a minimum. This
includes the lead length of the suppression element.
In addition to minimizing conductor length the following
printed-circuit board layout guidelines are recommended:
1. Place the suppression element close to the input
terminals or connectors.
2. Keep parallel signal paths to a minimum.
3. Avoid running protection conductors in parallel with
unprotected conductors.
4. Minimize all printed-circuit board loop areas including
power and ground loops.
5. Minimize the length of the transient return path to
ground.
6. Avoid using shared transient return paths to a common
ground point.
