P6002A Teccor Electronics, Inc., P6002A Datasheet - Page 182

• Manufacturer Part Number: P6002A
• Description: solid state crowbar devices
• Manufacturer: Teccor Electronics, Inc.

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3. Because traces exhibit a certain level of inductance, keep the length of the ground trace
For example, assume circuit A is protected by a P3100SC with a V
ground trace one inch in length and a self-inductance equal to 2.4 µH/inch. Assume
circuit B has the identical characteristics as Circuit A, except the ground trace is five inches
in length instead of one inch in length. If both circuits are surged with a 100 A, 10x1000 µs
wave-form, the results would be as shown in Table 5.2:
Table 5.2 Overshoot Caused by Trace Inductance
Other practices to ensure sound grounding techniques are:
1. Cross signal grounds and earth grounds perpendicularly in order to minimize the field
2. Make sure that the ground fingers on any edge connector extend farther out than any
on the PCB as short as possible in order to minimize its voltage contribution during a
transient condition. In order to determine the actual voltage contributed to trace
inductance, use the following equations:
effects of “noisy” power supplies.
power or signal leads in order to guarantee that the ground connection invariably is
connected first.
Circuit A
Circuit B
V = L (di/dt)
L = 0.0051 r [log
where r = length of trace
G = function of thickness and width as provided in Table 5.3
t = trace thickness
w = trace width
V
V
L
L
= 12 µH (100 A/10 µs) = 120 V
= 2.4 µH (100 A/10 µs) = 24 V
e
2 r/(t+w) +½ - log
V
L
= L (di/dt)
5 - 20
e
G] in µH
SIDACtor device V
SIDACtor
300 V
300 V
®
Data Book and Design Guide
© 2002 Teccor Electronics
S
S
equal to 300 V and a
Total protection level
(V
324 V
420 V
L
+ V
S
)