[SI-LIST] : RF & Digital

Jan Vercammen (jvercamm@roam.agfa.be)
Thu, 12 Aug 1999 08:58:31 +0200

Lum,

We have used following 10-layer stack up (full digital design):

L1 : signal
L2: signal
L3 : gnd
L4: power 1
L5: signal (strip line)
L6: signal (strip line)
L7: gnd
L8: power 2
L9: signal
L10: signal

I have named the 5V en 2.5V power and the ground gnd. The power planes 5V and
2.5V could be switched, depending on the circuit.

The setup as three advantages:

(1) There is a set of 3 pairs of signal layers, each pair is
uncoupled from the other pairs and in each pair one can route x and y.
Crosstalk is only a concern in the same layer!

(2) The power-gnd planes are well coupled, in our specific buildup the spacing is a low
160microns.

(3) The setup is symmetric!

A disadvantage is possibly the difference in impedance between the three pairs, however
this can be controlled with the track width. Also, critical signals, clocks, control ...
could be x-y routed in the strip line layers L5 and L6.

regards,

jan vercammen

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