DEMO-HMPP-389T Datasheet, PDF (4/12 Pages) Broadcom Corporation. – MiniPak Surface Mount RF PIN Switch Diodes

Typical Applications
RF COMMON
2
1
RF 1
BIAS 1
3
4
RF 2
BIAS 2
RF COMMON
3
4
3
4
RF 1
RF 2
2
1
2
1
Figure 6. Simple SPDT Switch Using Only Positive Bias.
RF COMMON
3
4
RF 1
2
1
4
1
3
2
3
4
2
1
BIAS
Figure 8. Very High Isolation SPDT Switch, Dual Bias.
BIAS
Figure 7. High Isolation SPDT Switch Using Dual Bias.
N+ Diffusion
Metal Contact
Bulk
I-Layer
Bulk Attenuator Diode
P+ Diffusion
RF 2
Epi
I-Layer
Contact Over
P+ Diffusion
Epi Switching Diode
Figure 9. PIN Diode Construction.
N+ Substrate
Applications Information
PIN Diodes
In RF and microwave networks, mechanical switches and
attenuators are bulky, often unreliable, and difficult to
manufacture. Switch ICs, while convenient to use and
low in cost in small quantities, suffer from poor distortion
performance and are not as cost effective as PIN diode
switches and attenuators in very large quantities. For over
30 years, designers have looked to the PIN diode for high
performance/low cost solutions to their switching and
level control needs.
In the RF and microwave ranges, the switch serves the
simple purpose which is implied by its name; it operates
between one of two modes, ON or OFF. In the ON state,
the switch is designed to have the least possible loss. In
the OFF state, the switch must exhibit a very high loss
(isolation) to the input signal, typically from 20 to 60 dB.
The attenuator, however, serves a more complex func-
tion. It provides for the“soft”or controlled variation in the
power level of a RF or microwave signal. At the same time
as it attenuates the ­input signal to some predetermined
value, it must also present a matched input impedance
(low VSWR) to the source. Every microwave network which
uses PIN ­diodes (phase shifter, modulator, etc.) is a varia-
tion on one of these two basic circuits.
One can see that the switch and the attenuator are quite
different in their function, and will therefore often ­require
different characteristics in their PIN diodes. These proper-
ties are easily controlled through the way in which a PIN
diode is fabricated. See Figure 14.