B1201U
| Model | B1201U |
| Description | solid state crowbar devices |
| PDF file | Total 212 pages (File size: 2M) |
| Chip Manufacturer | TECCOR |
PCB Layout
3. Because traces exhibit a certain level of inductance, keep the length of the ground trace
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:
V = L (di/dt)
L = 0.0051
r
[log
e
2
r/(t+w)
+�½ - log
e
G] in µH
where
r
= length of trace
G = function of thickness and width as provided in Table 5.3
t = trace thickness
w = trace width
For example, assume circuit A is protected by a P3100SC with a V
S
equal to 300 V and a
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
V
L
= L (di/dt)
Circuit A
Circuit B
V
L
= 2.4 µH (100 A/10 µs) = 24 V
V
L
= 12 µH (100 A/10 µs) = 120 V
SIDACtor
device V
S
300 V
300 V
Total protection level
(V
L
+ V
S
)
324 V
420 V
Other practices to ensure sound grounding techniques are:
1. Cross signal grounds and earth grounds perpendicularly in order to minimize the field
effects of “noisy” power supplies.
2. Make sure that the ground fingers on any edge connector extend farther out than any
power or signal leads in order to guarantee that the ground connection invariably is
connected first.
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© 2002 Teccor Electronics
Data Book and Design Guide
