ADUC836 datasheet(21/80 Pages) AD

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ADuC836

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ADuC836

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SF (Sinc Filter Register)

The number in this register sets the decimation factor and thus

the output update rate for the primary and auxiliary ADCs.This

SFR cannot be written by user software while either ADC is active.

The update rate applies to both primary and auxiliary ADCs and

is calculated as follows:

ADC

MOD

= ×

where:

fADC = ADC Output Update Rate

fMOD = Modulator Clock Frequency = 32.768 kHz

SF = Decimal Value of SF Register

The allowable range for SF is 0DH to FFH. Examples of SF

values and corresponding conversion update rates (fADC) and con-

version times (tADC) are shown in TableVIII.The power-on default

value for the SF Register is 45H, resulting in a default ADC update

rate of just under 20 Hz. Both ADC inputs are chopped to mini-

mize offset errors, which means that the settling time for a single

conversion, or the time to a first conversion result in Continuous

Conversion mode, is 2  tADC. As mentioned earlier, all calibra-

tion cycles will be carried out automatically with a maximum, i.e.,

FFH, SF value to ensure optimum calibration performance. Once

a calibration cycle has completed, the value in the SF Register will

be that programmed by user software.

Table VIII. SF SFR Bit Designations

SF(dec)

SF(hex)

fADC(Hz)

tADC(ms)

105.3

9.52

19.79

50.34

255

5.35

186.77

ICON (Current Sources Control Register)

The icon SFR is used to control and configure the various excitation and burnout current source options available on-chip.

SFR Address

D5H

Power-On Default Value

00H

Bit Addressable

Table IX. ICON SFR Bit Designations

Bit

Name

Description

–––

Reserved for Future Use

Burnout Current Enable Bit.

Set by user to enable both transducer burnout current sources in the primary ADC signal paths.

Cleared by the user to disable both transducer burnout current sources.

ADC1IC

Auxiliary ADC Current Correction Bit. Set by user to allow scaling of the auxiliary ADC by an internal current

source calibration word.

ADC0IC

Primary ADC Current Correction Bit.

Set by user to allow scaling of the primary ADC by an internal current source calibration word.

I2PIN*

Current Source-2 Pin Select Bit.

Set by user to enable current source-2 (200 A) to external Pin 3 (P1.2/DAC/IEXC1).

Cleared by user to enable current source-2 (200 A) to external Pin 4 (P1.3/AIN5/IEXC2).

I1PIN*

Current Source-1 Pin Select Bit.

Set by user to enable current source-1 (200 A) to external Pin 4 (P1.3/AIN5/IEXC2).

Cleared by user to enable current source-1 (200 A) to external Pin 3 (P1.2/DAC/IEXC1).

I2EN

Current Source-2 Enable Bit.

Set by user to turn on excitation current source-2 (200 A).

Cleared by user to turn off excitation current source-2 (200 A).

I1EN

Current Source-1 Enable Bit.

Set by user to turn on excitation current source-1 (200 A).

Cleared by user to turn off excitation current source-1 (200 A).

*Both current sources can be enabled to the same external pin, yielding a 400 A current source.

REV. A

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