Quad Capacitance
Capacitance of Schottky diode quads is measured using
an HP4271 LCR meter. This instrument effectively isolates
individual diode branches from the others, allowing ac‑
curate capacitance measurement of each branch or each
diode. The conditions are: 20 mV R.M.S. voltage at 1 MHz.
Avago defines this measurement as “CM”, and it is equiva‑
lent to the capacitance of the diode by itself. The equiva‑
lent diagonal and adjacent capaci‑tances can then be cal‑
culated by the formulas given below.
In a quad, the diagonal capacitance is the capacitance be‑
tween points A and B as shown in the figure below. The
diagonal capacitance is calculated using the following
formula
C
3
x C
4
C
1
x C
2
C
DIAGONAL
= _______ + _______
C
1
+ C
2
C
3
+ C
4
The equivalent x C
2
C
1
adjacentCcapacitance is the capacitance
3
xC
4
C
DIAGONAL
= _______ + _______
1 the figure below. This capaci‑
between points + ____________
A and C in
C
ADJACENT
= C
1
+ C
C
1
C
3
+ C
4
2
tance is calculated using the following formula
1 1
1
–– + –– + ––
1
C
2
C
3
C
C
ADJACENT
= C
1
+ ____________
4
1 1
1
–– + ––
8.33 X 10
-5
nT
+ ––
R
j
=
I +
C
2
C
3
C
4
I
b
s
Linear Equivalent Circuit Model Diode Chip
R
j
R
S
C
j
R
S
= series resistance (see Table of SPICE parameters)
C
j
= junction capacitance (see Table of SPICE parameters)
R
j
=
8.33 X 10
-5
nT
I
b
+ I
s
where
I
b
= externally applied bias current in amps
I
s
= saturation current (see table of SPICE parameters)
T = temperature,
°K
n = ideality factor (see table of SPICE parameters)
Note:
To effectively model the packaged HSMS-282x product,
please refer to Application Note AN1124.
ESD WARNING:
Handling Precautions Should Be Taken To Avoid Static Discharge.
This information does
-5
nT
apply to cross‑over quad di‑
8.33 X 10
not
R
j
=
odes.
I
b
+ I
s
C
1
C
C
2
C
4
B
C
3
A
SPICE Parameters
Parameter
B
V
C
J0
E
G
I
BV
I
S
N
R
S
P
B
P
T
M
Ω
V
Units
V
pF
eV
A
A
HSMS-282x
15
0.7
0.69
1E‑4
2.2E‑8
1.08
6.0
0.65
2
0.5
3
AVAGO [ AVAGO TECHNOLOGIES LIMITED ]
