MCP33131 datasheet(33/54 Pages) MICROCHIP

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DS20006122A-page 33

MCP33131/MCP33121/MCP33111-XX

EQUATION 6-7:

NOISE DENSITY FOR ADC

INPUT DRIVER

Using Equation 6-7, the recommended maximum

noise voltage density limit for unity gain input driver for

single-ended input ADC can be estimated. Table 6-1 to

Table 6-3 show a few example results with GN = 1. The

user may use these tables as a reference when

selecting the ADC input driver amplifier.

TABLE 6-1:

Noise Voltage Density (eN) of

Input Driver for MCP33131-XX

TABLE 6-2:

Noise Voltage Density (eN) of

Input Driver for MCP33121-XX

TABLE 6-3:

Noise Voltage Density (eN) of

Input Driver for MCP33111-XX

ADC

(Note 1)

Filter

ADC Input Driver

Amplifier (GN = 1)

VREF

SNR

(dBFS)

ADC

Input-Referred

Noise

(Table 2)

Noise Voltage

Density (eN)

2.5V

78.8

V

3 MHZ

7.3 nV/√Hz

4 MHz

6.3 nV/√Hz

5 MHZ

5.6 nV/√Hz

3.3V

82.6

V

3 MHZ

7.6 nV/√Hz

4 MHz

6.6 nV/√Hz

5 MHZ

5.9 nV/√Hz

V

3 MHZ

7.3 nV/√Hz

4 MHz

6.3 nV/√Hz

5 MHZ

5.6 nV/√Hz

Note

See Equation 6-4 for the ADC input-referred noise

calculation for single-ended input.

fB is -3dB bandwidth of the RC anti-aliasing filter.

-----------





------



GN  fB

--------------------------

VREF 10

SNR

-----------

–

---



VN_ADC Input-Referred Noise

-------

 f

ADC

(Note 1)

Filter

ADC Input Driver

Amplifier (GN = 1)

VREF

SNR

(dBFS)

ADC

Input-Referred

Noise

(Note 2)

Noise Voltage

Density (eN)

2.5V

88.4

V

3 MHZ

8.1 nV/√Hz

4 MHz

7.1 nV/√Hz

5 MHZ

6.3 nV/√Hz

3.3V

81.5

98.2

V

3 MHZ

9.0 nV/√Hz

4 MHz

7.8 nV/√Hz

5 MHZ

7.0 nV/√Hz

83.5

118.1

V

3 MHZ

10.9 nV/√Hz

4 MHz

9.4 nV/√Hz

5 MHZ

8.4 nV/√Hz

Note

See Equation 6-4 for the ADC input-referred noise

calculation for single-ended input.

fB is -3dB bandwidth of the RC anti-aliasing filter.

ADC

(Note 1)

Filter

ADC Input Driver

Amplifier (GN = 1)

VREF

SNR

(dBFS)

ADC

Input-Referred

Noise

(Note 2)

Noise Voltage

Density (eN)

2.5V

73.2

193.3

V

3 MHZ

17.8 nV/√Hz

4 MHz

15.4 nV/√Hz

5 MHZ

13.8 nV/√Hz

3.3V

73.5

246.6

V

3 MHZ

22.7 nV/√Hz

4 MHz

19.7 nV/√Hz

5 MHZ

17.6 nV/√Hz

73.8

360.9

V

3 MHZ

33.3 nV/√Hz

4 MHz

28.8 nV/√Hz

5 MHZ

25.8 nV/√Hz

Note

See Equation 6-4 for the ADC input-referred noise cal-

culation for single-ended input.

fB is -3dB bandwidth of the RC anti-aliasing filter.

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