HMPP-389x Series
Data Sheet
MiniPak Surface Mount RF PIN Switch Diodes
Description/Applications
These ultra-miniature products represent the blending of
Avago Technologies’ proven semiconductor and the latest
in leadless packaging technology.
The HMPP-389x series is optimized for switching applications
where low resistance at low current and low capacitance
are required. The MiniPak package offers reduced parasitics
when compared to conventional leaded diodes, and lower
thermal resistance.
Low junction capacitance of the PIN diode chip, combined
with ultra low package parasitics, mean that these prod-
ucts may be used at frequencies which are higher than
the upper limit for conventional PIN diodes.
Note that Avago’s manufacturing techniques assure that
dice packaged in pairs are taken from adjacent sites on
the wafer, assuring the highest degree of match.
The HMPP-389T low inductance wide band shunt switch
is well suited for applications up to 6 GHz.
Minipak 1412 is a ceramic based package, while Minipak
QFN is a leadframe based package.
Features
•
Surface mount MiniPak package
•
Better thermal conductivity for higher power dissipa-
tion
•
Single and dual versions
•
Matched diodes for consistent performance
•
Low capacitance
•
Low resistance at low current
•
Low FIT (Failure in Time) rate*
•
Six-sigma quality level
* For more information, see the Surface Mount Schottky Reliability
Data Sheet.
Pin Connections and Package Marking
3
AA
4
2
1
Package Lead Code Identification (Top View)
Single
3
2
#0
(Minipak 1412)
Shunt Switch
Cathode
Anode
3
4
4
1
3
2
#2
(Minipak 1412)
Anti-parallel
4
1
3
2
#5
(Minipak 1412)
Parallel
4
1
Product code
Date code
Notes:
1. Package marking provides orientation and
identification.
2. See “Electrical Specifications” for appropri-
ate package marking.
2
Anode
T
Cathode
1
Typical Applications
RF COMMON
RF COMMON
2
1
RF 1
3
4
RF 2
RF 1
2
1
2
1
3
4
3
4
RF 2
BIAS 1
BIAS 2
BIAS
Figure 6. Simple SPDT Switch Using Only Positive Bias.
Figure 7. High Isolation SPDT Switch Using Dual Bias.
RF COMMON
N+ Diffusion
Metal Contact
4
3
RF 1
2
4
1
3
1
2
3
2
4
1
RF 2
Bulk
I-Layer
Bulk Attenuator Diode
Contact Over
P+ Diffusion
P+ Diffusion
Epi
I-Layer
BIAS
Epi Switching Diode
N+ Substrate
Figure 8. Very High Isolation SPDT Switch, Dual Bias.
Figure 9. PIN Diode Construction.
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.
4
Diode Construction
At Avago Technologies, two basic methods of diode fabri-
cation are used. In the case of bulk diodes, a wafer of very
pure (intrinsic) silicon is heavily doped on the top and
bottom faces to form P and N regions. The result is a diode
with a very thick, very pure I region. The epitaxial layer (or
EPI) diode starts as a wafer of heavily doped silicon (the
P or N layer), onto which a thin I layer is grown. After the
epitaxial growth, diffusion is used to add a heavily doped
(N or P) layer on the top of the epi, creating a diode with
a very thin I layer populated by a relatively large number
of imperfections.
These two different methods of design result in two
classes of diode with distinctly different characteristics,
as shown in Table 1.
Table 1. Bulk and EPI Diode Characteristics.
Characteristic
Lifetime
Distortion
Current Required
I Region Thickness
EPI Diode
Short
High
Low
Very Thin
Bulk Diode
Long
Low
High
Thick
to mention that in this frequency range, the diode can
exhibit very strong capacitive or inductive reactance — it
will not behave at all like a resistor. However, at zero bias
or under heavy forward bias, all PIN diodes demonstrate
very high or very low impedance (respectively) no matter
what their lifetime is.
Diode Resistance vs. Forward Bias
If we look at the typical curves for resistance vs. forward
current for bulk and epi diodes (see Figure 15), we see
that they are very different. Of course, these curves apply
only at frequencies > 10 f
C
. One can see that the curve
of resistance vs. bias current for the bulk diode is much
higher than that for the epi (switching) diode. Thus, for a
given current and junction capacitance, the epi diode will
always have a lower resistance than the bulk diode. The
thin epi diode, with its physically small I region, can easily
be saturated (taken to the point of minimum resistance)
with very little current compared to the much larger bulk
diode. While an epi diode is well saturated at currents
around 10 mA, the bulk diode may require upwards of
100 mA or more. Moreover, epi diodes can achieve rea-
sonable values of resistance at currents of 1 mA or less,
making them ideal for battery operated applications.
Having compared the two basic types of PIN diode, we
will now focus on the HMPP-3890 epi diode.
Given a thin epitaxial I region, the diode designer can
trade off the device’s total resistance (R
S
+ R
j
) and junction
capacitance (C
j
) by varying the diameter of the contact
and I region. The HMPP-3890 was designed with the 930
MHz cellular and RFID, the 1.8 GHz PCS and 2.45 GHz RFID
markets in mind. Combining the low resistance shown
in Figure 15 with a typical total capacitance of 0.27 pF, it
forms the basis for high performance, low cost switching
networks.
1000
HSMP-3880 Bulk PIN Diode
As we shall see in the following paragraphs, the bulk diode
is almost always used for attenuator applications and
sometimes as a switch, while the epi diode (such as the
HMPP-3890) is generally used as a switching element.
Diode Lifetime and Its Implications
The resistance of a PIN diode is controlled by the conductiv-
ity (or resistivity) of the I layer. This conductivity is controlled
by the density of the cloud of carriers (charges) in the I layer
(which is, in turn, controlled by the DC bias). Minority car-
rier lifetime, indicated by the Greek symbol
τ,
is a measure
of the time it takes for the charge stored in the I layer to
decay, when forward bias is replaced with reverse bias, to
some predetermined value. This lifetime can be short (35
to 200 nsec. for epitaxial diodes) or it can be relatively long
(400 to 3000 nsec. for bulk diodes). Lifetime has a strong
influence over a number of PIN diode parameters, among
which are distortion and basic diode behavior.
To study the effect of lifetime on diode behavior, we first
define a cutoff frequency f
C
= 1/τ. For short lifetime diodes,
this cutoff frequency can be as high as 30 MHz while for
our longer lifetime diodes f
C
≅
400 KHz. At frequencies
which are ten times f
C
(or more), a PIN diode does indeed
act like a current controlled variable resistor. At frequen-
cies which are one tenth (or less) of f
C
, a PIN diode acts
like an ordinary PN junction diode. Finally, at 0.1f
C
≤ f ≤
10f
C
, the behavior of the diode is very complex. Suffice it
RESISTANCE ( )
100
10
HMPP-389x
Epi PIN Diode
1
0.01
0.1
1
10
BIAS CURRENT (mA)
100
Figure 10. Resistance vs, Forward Bias.
Figure 10. Resistance vs. Forward Bias.
5
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