MCP4441 datasheet(94/100 Pages) MICROCHIP

94 / 100 page

MCP444X/446X

DS22265A-page 94

Using the simulation models of the NMOS and PMOS

devices for the MCP44XX 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

VIN voltage is increased. The wiper resistance (RW) is

simply the parallel resistance on the NMOS and PMOS

devices (RW = RNMOS || RPMOS). Below the threshold

voltage for the NMOS ad PMOS devices, the

resistance becomes very large (Gigaohms). In the

transistors 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 (RNMOS, RPMOS) and

Wiper Resistance (RW) VS. VIN

(VDD = 3.0V).

FIGURE B-12:

NMOS and PMOS

Transistor Resistance (RNMOS, RPMOS) and

Wiper Resistance (RW) VS. VIN

(VDD = 1.8V).

FIGURE B-13:

NMOS and PMOS

Transistor Resistance (RNMOS, RPMOS) and

Wiper Resistance (RW) VS. VIN

(VDD = 3.0V).

FIGURE B-14:

NMOS and PMOS

Transistor Resistance (RNMOS, RPMOS) and

Wiper Resistance (RW) VS. VIN

(VDD = 1.8V).

NMOS

PMOS

VG (VDD/VSS)

“gate”

VOUT

VIN

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

VIN Voltage

500

1000

1500

2000

2500

RPMOS

RNMOS

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

VIN Voltage

100

120

140

160

RPMOS

RNMOS

PMOS

Theshold

NMOS

Theshold

100

150

200

250

300

0.0

0.6

1.2

1.8

2.4

3.0

VIN Voltage

RPMOS

RNMOS

500

1000

1500

2000

2500

3000

3500

4000

4500

5000

0.0

0.3

0.6

0.9

1.2

1.5

1.8

VIN Voltage

RPMOS

RNMOS

MCP4441 Datasheet(PDF) 94 Page - Microchip Technology

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