MCP3465R datasheet(38/110 Pages) MICROCHIP

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MCP3465R

DS20006414C-page 38

 2020-2021 Microchip Technology Inc.

EQUATION 5-1:

TEMPERATURE SENSOR TRANSFER FUNCTION

5.1.3

ADC OFFSET CANCELLATION

ALGORITHM

The input multiplexer and the ADC include an offset can-

cellation algorithm that cancels the offset contribution of

the ADC. This offset cancellation algorithm is controlled

by the AZ_MUX bit in the CONFIG2 register. When

AZ_MUX = 0 (default), the offset cancellation algorithm is

disabled and the conversions are not affected by this

setting. When AZ_MUX = 1, the algorithm is enabled.

When the offset cancellation algorithm is enabled, ADC

takes two conversions, one with the differential input as

VIN+/VIN-, one with VIN+/VIN- inverted. Equation 5-2

calculates the ADC output code. When AZ_MUX = 1, the

Conversion Time, TCONV, is multiplied by two, compared

to the default case where AZ_MUX = 0.

EQUATION 5-2:

AZ_MUX CONVERSION RESULT

This technique allows the cancellation of the ADC

offset error and the achievement of ultra-low offset

without any digital calibration. The resulting offset is the

residue of the difference between the two conversions,

which is on the order of magnitude of the noise floor.

This offset is effectively canceled at every conversion,

so the residual offset error temperature drift is

extremely low.

For One-Shot mode, the conversion time is simply

multiplied by two. Enabling the AZ_MUX bit is not

compatible with the Continuous Conversion mode

(because it effectively multiplexes the inputs in

between each conversion). If AZ_MUX = 1 and

CONV_MODE[1:0] = 11 (Continuous Conversion

mode), the device will reset the digital filter in between

each conversion, and will therefore, have an output

data rate of 1/(2 * TCONV). The Continuous mode is

replaced by a series of One-Shot mode conversions

with no delay in between each conversion (see

Section 5.14 “Conversion Modes” and Figure 5-5 for

more details about the Conversion modes).

First-order (linear) fitting: Gain = 1, MCLK = 4.9152 MHz, DATA_FORMAT[1:0] = 00

TEMP

C



4.0096 10

–





ADCDATA LSb





VREF V

 269.13

–



VIN mV



0.2973 TEMP (

C) 80



Where VREF =VREF+–VREF-

ADC Output Code (AZ_MUX = 1)

ADC Output at + VIN



ADC Output at -VIN



–

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