Datasheet

MCP453X/455X/463X/465X
DS22096B-page 96  2008-2013 Microchip Technology Inc.
Using the simulation models of the NMOS and PMOS
devices for the MCP4XXX analog switch (Figure B-10),
we plot the device resistance when the devices are
turned on. Figure B-11 and Figure B-12 show the
resistances of the NMOS and PMOS devices as the
V
IN
voltage is increased. The wiper resistance (R
W
) is
simply the parallel resistance on the NMOS and PMOS
devices (R
W
= R
NMOS
|| R
PMOS
). Below the threshold
voltage for the NMOS and PMOS devices, the
resistance becomes very large (Giga s). In the
transistor’s active region, the resistance is much lower.
For these graphs, the resistances are on different
scales. Figure B-13 and Figure B-14 only plot the
NMOS and PMOS device resistance for their active
region and the resulting wiper resistance. For these
graphs, all resistances are on the same scale.
FIGURE B-10: Analog Switch.
FIGURE B-11: NMOS and PMOS
Transistor Resistance (R
NMOS
, R
PMOS
) and
Wiper Resistance (R
W
) VS. V
IN
(V
DD
= 3.0V).
FIGURE B-12: NMOS and PMOS
Transistor Resistance (R
NMOS
, R
PMOS
) and
Wiper Resistance (R
W
) VS. V
IN
(V
DD
= 1.8V).
FIGURE B-13: NMOS and PMOS
Transistor Resistance (R
NMOS
, R
PMOS
) and
Wiper Resistance (R
W
) VS. V
IN
(V
DD
= 3.0V).
FIGURE B-14: NMOS and PMOS
Transistor Resistance (R
NMOS
, R
PMOS
) and
Wiper Resistance (R
W
) VS. V
IN
(V
DD
= 1.8V).
R
W
NMOS
PMOS
V
G
(V
DD
/V
SS
)
“gate”
“gate”
V
OUT
V
IN
0.00E+00
5.00E+09
1.00E+10
1.50E+10
2.00E+10
2.50E+10
3.00E+10
0.0 0.3 0.6 0.9 1.2 1.5 1.8
V
IN
Voltage
NMOS and PMOS Resistance
()
0
500
1000
1500
2000
2500
Wiper Resistance ()
R
PMOS
R
NMOS
R
W
PMOS
Theshold
NMOS
Theshold
0.00E+00
1.00E+09
2.00E+09
3.00E+09
4.00E+09
5.00E+09
6.00E+09
7.00E+09
0.0 0.6 1.2 1.8 2.4 3.0
V
IN
Voltage
NMOS and PMOS Resistance
()
0
20
40
60
80
100
120
140
160
Wiper Resistance ()
R
PMOS
R
NMOS
R
W
PMOS
Theshold
NMOS
Theshold
0
50
100
150
200
250
300
0.0 0.6 1.2 1.8 2.4 3.0
V
IN
Voltage
Resistance ()
R
PMOS
R
NMOS
R
W
0
500
1000
1500
2000
2500
3000
3500
4000
4500
5000
0.0 0.3 0.6 0.9 1.2 1.5 1.8
V
IN
Voltage
Resistance ()
R
PMOS
R
NMOS
R
W