HSMS-2829 Datasheet, PDF (5/15 Pages) Broadcom Corporation. – Surface Mount RF Schottky Barrier Diodes

Applications Information
Product Selection
Avago’s family of surface mount Schottky diodes provide
unique solutions to many design problems. Each is opti‑
mized for certain applications.
The first step in choosing the right product is to select the
diode type. All of the products in the HSMS‑282x fami‑
ly use the same diode chip – they differ only in package
configuration. The same is true of the HSMS-280x, -281x,
285x, -286x and -270x families. Each family has a different
set of characteristics, which can be compared most easily
by consulting the SPICE parameters given on each data
sheet.
The HSMS‑282x family has been optimized for use in RF
applications, such as
• DC biased small signal detectors to 1.5 GHz.
• Biased or unbiased large signal detectors (AGC or
power monitors) to 4 GHz.
• Mixers and frequency multipliers to 6 GHz.
The other feature of the HSMS‑282x family is its unit‑to‑unit
and lot‑to‑lot consistency. The silicon chip used in this se‑
ries has been designed to use the fewest possible process‑
ing steps to minimize variations in diode characteristics.
Statistical data on the consistency of this product, in terms
of SPICE parameters, is available from Avago.
For those applications requiring very high breakdown
voltage, use the HSMS‑280x family of diodes. Turn to the
HSMS‑281x when you need very low flicker noise. The
HSMS‑285x is a family of zero bias detector diodes for small
signal applications. For high frequency detector or mixer
applications, use the HSMS‑286x family. The HSMS‑270x
is a series of specialty diodes for ultra high speed clipping
and clamping in digital circuits.
Schottky Barrier Diode Characteristics
Stripped of its package, a Schottky barrier diode chip con‑
sists of a metal-semiconductor barrier formed by deposi‑
tion of a metal layer on a semiconductor. The most com‑
mon of several different types, the passivated diode, is
shown in Figure 10, along with its equivalent circuit.
R_S is the parasitic series resistance of the diode, the sum
of the bondwire and leadframe resistance, the resistance
of the bulk layer of silicon, etc. RF energy coupled into R_S
is lost as heat—it does not contribute to the rectified out‑
put of the diode. C_J is parasitic junction capacit­ ance of the
diode, controlled by the thick-ness of the epitaxial layer
and the diameter of the Schottky contact. R_j is the junc‑
tion resistance of the diode, a function of the total current
flowing through it.
8.33 X 10 ^-5 nT
R
j⁼
––––––––––––
I _S+I_b
=R _V–R_s
≈0–.0–2–6–– at 25 °C
I _S+I_b
where
n=
–^V–^-–^IR––^S
i^Id⁼ea^I l^Sit⁽y^e
0.026
factor
–_(s1_e)_e
table
of
SPICE
parameters)
T = temperature in °K
I_S = saturation current (see table of SPICE parameters)
I_b = externally applied bias current in amps
R_v = sum of junction and series resistance, the slope of
the V-I curve
I_S is a function of diode barrier height, and can range from
picoamps for high barrier diodes to as much as 5 µA for
very low barrier diodes.
8.33 X 10 ^-5 nT
T_Th_he_eH_ce_u^Rig_rrhj_e⁼t_no_tf^–_-v^–th_I–oe^–_lt^–S_Sa^–c_g+h^–_eo^–I t^–_bct^–k_h^–y_a^–B_raa⁼_cr_t^Rr_eieV_rr_­is^–_t^R_ics_{of a Schottky barrier}
deqioudaetioatn_≈r:o_0Io_{–.0S–}m_{2–+6–}t_I–e_bm_ap_t e₂r₅a_°t_Cure is described by the following
–^V–^-–^IR––^S
I = I _S (e ^0.026 – 1)
On a semi-log plot (as shown in the Avago catalog) the
current graph will be a straight line with inverse slope 2.3
X 0.026 = 0.060 volts per cycle (until the effect of R_S is seen
in a curve that droops at high current). All Schottky diode
curves have the same slope, but not necessarily the same
value of current for a given voltage. This is deter­mined
by the saturation current, I_S, and is related to the barrier
height of the diode.
Through the choice of p-type or n‑type silicon, and the
selection of metal, one can tailor the characteristics of a
Schottky diode. Barrier height will be altered, and at the
same time C_J and R_S will be changed. In general, very low
barrier height diodes (with high values of I_S, suitable for
zero bias applica­tions) are realized on p-type silicon. Such
diodes suffer from higher values of R_S than do the n‑type.
METAL
R_S
PASSIVATION
PASSIVATION
N-TYPE OR P-TYPE EPI LAYER
SCHOTTKY JUNCTION
C_j
R_j
N-TYPE OR P-TYPE SILICON SUBSTRATE
CROSS-SECTION OF SCHOTTKY
BARRIER DIODE CHIP
Figure 10. Schottky Diode Chip.
EQUIVALENT
CIRCUIT
5