DEMO-HSMP-389V Datasheet, PDF (7/13 Pages) Broadcom Corporation. – Surface Mount RF PIN Switch Diodes

Typical Applications for HSMP-489x Low Inductance Series
Microstrip Series Connection for HSMP-489x Series
In order to take full advantage of the low inductance
of the HSMP‑489x series when using them in series ap-
plications, both lead 1 and lead 2 should be connected
together, as shown in Figure 17.
3
Equivalent Circuit Model
HSMP-389x Chip*
R_s
R_j
0.5
C_j
1
2
HSMP-489x
Figure 16. Internal Connections.
0.12 pF*
* Measured at -20 V
R_T = 0.5 + R_j
C_T = C_P + C_j
R_j
=
20
I^0.9
I = Forward Bias Current in mA
* See AN1124 for package models
Figure 17. Circuit Layout.
Microstrip Shunt Connections for HSMP-489x Series
In Figure 18, the center conductor of the microstrip
line is interrupted and leads 1 and 2 of the HSMP-489x
diode are placed across the resulting gap. This forces
the 1.5 nH lead inductance of leads 1 and 2 to appear as
part of a low pass filter, reducing the shunt parasitic in-
ductance and increasing the maximum available atten-
uation. The 0.3 nH of shunt inductance external to the
diode is created by the via holes, and is a good estimate
for 0.032" thick material.
50 OHM MICROSTRIP LINES
Co-Planar Waveguide Shunt Connection for HSMP-489x Series
Co-Planar waveguide, with ground on the top side of
the printed circuit board, is shown in Figure 20. Since
it eliminates the need for via holes to ground, it offers
lower shunt parasitic inductance and higher maximum
attenuation when compared to a microstrip circuit.
Co-Planar Waveguide
Groundplane
Center Conductor
Groundplane
Figure 20. Circuit Layout.
PAD CONNECTED TO GROUND
BY TWO VIA HOLES
Figure 18. Circuit Layout.
1.5 nH
1.5 nH
0.3 pF
0.3 nH
0.3 nH
Figure 19. Equivalent Circuit.
7
0.3 pF
0.75 nH
Figure 21. Equivalent Circuit.
A SPICE model is not available for PIN diodes as SPICE
does not provide for a key PIN diode characteristic, car-
rier lifetime.