ADUC836 datasheet(21/80 Pages) AD

21 / 80 page

REV. A

ADuC834

–21–

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 conversion

times (tADC) are shown in Table VIII. 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 minimize 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 calibration 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)

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

6BOBurnout Current Enable Bit.

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

Cleared by 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.

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