MCP33131 datasheet(36/54 Pages) MICROCHIP

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DS20006122A-page 36

 2018 Microchip Technology Inc.

MCP33131/MCP33121/MCP33111-XX

6.5

Transfer Function

The pseudo-differential analog input is:

VIN = (VIN+) - (VIN-)

where VIN+ is the analog input voltage at AIN+ pin with

respect to the ground reference (GND), and Vin- is the

voltage at AIN- pin, which is 0V when tied to the analog

input ground reference (GND).

The LSB size is given by Equation 6-10. and an

example of LSB size vs. reference voltage is

summarized in Table 6-6.

EQUATION 6-10:

LSB SIZE - EXAMPLE

where N is the resolution of the ADC in bits.

TABLE 6-6:

LSB SIZE VS. REFERENCE

Figure 6-5 shows the ideal transfer function and

Table 6-7 shows the digital output codes for the

MCP33131/MCP33121/MCP33111-XX.

FIGURE 6-5:

Ideal Transfer Function.

TABLE 6-5:

SPI CLOCK SPEED VS. INPUT ACQUISITION TIME (TACQ) FOR MCP331X1-05

Input

Acquisition Time:

tACQ (nS)

(Note 3)

Data

Conversion Time:

tCNV (nS)

(Note 4)

SPI Clock (fSCLK) Speed Requirement

(Note 1), (Note 2)

Sample Rate:

fS (kSPS)

Conditions

MCP33131-05

(16-bit)

MCP33121-05

(14-bit)

MCP33111-05

(12-bit)

700

1300

23.53MHz

20.59 MHz

17.65 MHz

500

-40°C ≤ TA ≤ 125°C

740

22.22 MHz

19.44 MHz

16.67 MHz

490

790

20.78 MHz

18.18 MHz

15.58 MHz

480

930

17.58 MHz

15.39 MHz

13.19 MHz

450

1200

13.56 MHz

11.86 MHz

10.17 MHz

400

1560

10.39 MHz

9.09 MHz

7.79 MHz

350

2030

7.96 MHz

6.97 MHz

5.97 MHz

300

2700

5.97 MHz

5.22MHz

4.48 MHz

250

3700

4.35 MHz

3.8 MHz

3.26 MHz

200

5370

2.99 MHz

2.62 MHz

2.25 MHz

150

8700

1.84 MHz

1.61 MHz

1.38 MHz

100

Note

This is the minimum SPI clock speed requirement to collect all N-bits of the ADC output during the input acquisition time (tACQ), when the

ADC is operating in continuous input sampling mode.

See Equation 6-9 for the calculation of the SPI clock speed requirement.

Input acquisition time (tACQ) is user-controllable.

Data conversion time (tCNV) is not user-controllable.

Reference

Voltage

(VREF)

LSB Size

MCP33131-XX

(16-bit)

MCP33121-XX

(14-bit)

MCP33111-XX

(12-bit)

2.5V

38.2

V

152.6

V

0.6104 mV

2.7V

41.2

V

164.8

V

0.6592 mV

45.8

V

183.1

V

0.7324 mV

3.3V

50.4

V

201.4

V

0.8057 mV

3.5V

53.4

V

213.6

V

0.8545 mV

61.0

V

244.1

V

0.9766 mV

4.5V

68.7

V

274.7

V

1.0986 mV

76.3

V

305.2

V

1.2207 mV

LSB

VREF

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

5.1

77.8

V311.3 V

1.2451 mV

VREF

Analog Input Voltage

VREF - 1 LSB

0V + 0.5 LSB

VREF - 1.5 LSB

Digital Output Code (Unipolar Straight Binary)

111 ...111

100 ...000

111 ...110

000 ...001

000 ...000

0V+ 1 LSB

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