MCP33151-05-ESLASHMS datasheet(33/55 Pages) MICROCHIP

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DS20006220A-page 33

MCP33151/41-XX

5.5

Transfer Function

The pseudodifferential analog input is:

VIN =(VIN+) – (VIN-), where VIN+ is the analog input

voltage at AIN+ pin with respect to the ground refer-

ence (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 5-10. and an

example of LSB size vs. reference voltage is

summarized in Table 5-3.

EQUATION 5-10:

LSB SIZE - EXAMPLE

TABLE 5-3:

LSB SIZE VS REFERENCE

Figure 5-6 shows the ideal transfer function and

Table 5-4 shows the digital output codes for the

MCP33151/41-XX.

FIGURE 5-6:

Ideal Transfer Function.

5.6

Digital Output Code

The digital output code is proportional to the input

voltage. The output data is in unipolar straight binary

format. The following is an example of the output code:

• for a zero or negative input:

Analog Input: VIN ≤ 0 (V)

Output Code: 0000...0000

• for a mid-scale input:

Analog Input: VIN = +VREF /2 (V)

Output Code: 1000...0000

• for a positive full-scale input:

Analog Input: VIN = +VREF (V)

Output Code: 1111...1111

The code will be locked at 1111...11 for all voltages

greater than (VREF – 1 LSB) and 0000...00 for

voltages less than 0V. Table 5-4 shows an example of

output codes of various input levels.

Reference

Voltage

(VREF)

LSB Size

MCP33151-XX

(14-bit)

MCP33141-XX

(12-bit)

1.8V

109.9 µV

439.5 µV

122.1 µV

488.3 µV

2.5V

152.6

V

0.6104 mV

183.1

V

0.7324 mV

3.3V

201.4

V

0.8057 mV

3.5V

213.6

V

0.8545 mV

244.1

V

0.9766 mV

4.5V

274.7

V

1.0986 mV

305.2

V

1.2207 mV

5.1

311.3

V

1.2451 mV

LSB

VREF

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

Where N is the resolution of the ADC in bits.

111 … 111

000 … 000

000 … 001

100 … 000

0V + 1 LSB

0V + 0.5 LSB

VREF

VREF - 1.5 LSB

VREF - 1 LSB

Analog Input Voltage

111 … 110

VREF - 2 LSB

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