DEMO-HSMS285-0 Datasheet, PDF (5/13 Pages) Broadcom Corporation. – Surface Mount Zero Bias Schottky Detector Diodes

Appli­cations Information
Introduction
Avago’s HSMS‑285x family of Schottky detector diodes
has been developed specifically for low cost, high
volume designs in small signal (P_in < -20 dBm) applica-
tions at frequencies below 1.5 GHz. At higher frequen-
cies, the DC biased HSMS-286x family should be consid-
ered.
In large signal power or gain control applications
(P_in> ‑20 dBm), the HSMS-282x and HSMS-286x prod-
ucts should be used. The HSMS-285x zero bias diode is
not designed for large signal designs.
Schottky Barrier Diode ­Characteristics
Stripped of its package, a Schottky barrier diode chip
­consists of a metal-semiconductor barrier formed by de-
position of a metal layer on a semiconductor. The most
common of several ­different types, the passivated ­diode,
is shown in Figure 5, along with its equivalent circuit.
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
EQUIVALENT
CIRCUIT
Figure 5. Schottky Diode Chip.
R_S is the parasitic series ­resistance of the diode, the sum
of the bondwire and leadframe ­resistance, the resistance
of the bulk layer^Ho^SMf ^Ss^-i²l⁸ic^5Ao^/6n^A, ^fe^igt⁹c. RF ­ energy coupled into
R_S is lost as heat — it does not contribute to the rectified
output of the diode. C_J is parasitic junction capaci­tance
of the diode, controlled by the thickness of the epitaxial
layer and the diameter of the Schottky contact. R_j is the
junction ­resistance of the diode, a function of the total
current flowing through it.
R_j=
8.33 X 10^-5
I_S + I_b
n
T
=
R_V–
R_s
0.026
=
at 25°C
I_S + I_b
where
( ) ⁿ
T
I_S
=
=
=
tis^Idea=metua^ISplri⁽_aet^e_tyr^x_iaof^ptanucrcte₀^oV_u.^ri_0r^-nr₂^(eIsR°₆^enKSet
table of SPICE parameters)
- 1)
(see table of SPICE parameters)
I_b = externally applied bias current in amps
If_Sroims apfiucon^R_ac^S_mti⁼opn^R_s^dof^–_ofrd⁰_hi^.oi⁰_gId_f²_he⁶_{bbaarrrrieierrdhioedigehst,toanads}
can range
much as 5
µA for very low barrier diodes.

R_V
≈
26,000
I_S + I_b
Th^Re^{j =}Hei⁸g^.h³t^3Io_S^Xf+t¹hI0_be^-5Sⁿch^To⁼tt^Rky^V–B^Ra^srrier
The curr₀e_.n₀t₂-v₆oltage character­istic of a Schottky barrier
deqioud⁼_aetiaotnr:Io_So₊m_Ibt^ae^tm²p⁵e^°Crature is described by the following
( ) I = I_S (exp
V - IR_S
0.026
- 1)
Oc2u.n3rrXae_Rn0Sset._{=0mg2Rr6ida-l–=pohg00.pw0.06lIiof2l0lt6vb(oaesltasshpsoterwraicngyhicntletli(hnueenAtwivl itathhgeoinecfvafeetracstleoogsf)lRotSphiees}
seen in a curve that droops at high current). All Schottky
­didlyieottdehre­emcs_{RiunaVmre≈}vd_{2eeI6bsSv,y+0ah0tlaIuh0b}veeesoatfhtcueurarsrtaeiomnntecfousrlroraepnget,i,vbIe_Su,natvnnodoltitsagrneeel.acTteehsdissatiros-
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, suit-
able for zero bias applica­tions) are realized on ­ p‑type
silicon. Such diodes suffer from higher values of R_S than
do the n‑type. Thus, p-type diodes are generally reserved
for small signal detector applications (where very high
values of R_V swamp out high R_S) and n-type diodes are
used for mixer applications (where high L.O. drive levels
keep R_V low).
Measuring Diode Parameters
The measurement of the five ­ elements which make up
the low frequency equivalent circuit for a pack­aged
Schottky diode (see ­Figure 6) is a complex task. ­Various
techniques are used for each element. The task begins
with the elements of the diode chip itself.
C_P
L_P
R_V
R_S
C_j
FOR THE HSMS-285x SERIES
C_P = 0.08 pF
L_P = 2 nH
C_j = 0.18 pF
R_S = 25 Ω
R_V = 9 KΩ
Figure 6. Equivalent Circuit of a Schottky Diode.