Figure 6.13: Estimating the area where the current will flow from the component
to the decoupling capacitor.
3. Determine the plane inductance between the package power pin and the nearest
decoupling capacitor. This can be approximated by constructing a rectangle with the
same area as the triangle shown in
Figure 6.13
and simulating it in a two-dimensional
solver as a wide transmission line with a length of D. Alternatively, the following
equation can be used [
Johnson and Graham, 1993
]:
(6.8)
4. where D is the length of the plane segment in inches, H the separation between the
power and ground planes (in inches), and W the width in inches. This should provide
an estimate that is accurate to at least one order of magnitude. If a more accurate
number is required, a three-dimensional simulator or laboratory measurements are
required.
Figure 6.14
shows an equivalent circuit of a GTL bus where three output buffers are sharing
one board level decoupling capacitor. A full model would include the crosstalk in the
package and socket.
Summary :
Figure 6.13: Estimating the area where the current will flow from the component to the decoupling capacitor. where D is the length of the plane segment in inches, H the separation between the power and ground planes (in inches), and W the width in inches.
Tags :
inches,figure,decoupling,capacitor,power,between,required,plane,area,package,length,accurate,613