MSC1202Y2RHHT datasheet(25/92 Pages) TI

25 / 92 page

MSC1200

MSC1201

MSC1202

SBAS317E − APRIL 2004 − REVISED MAY 2006

www.ti.com

For system calibration, the appropriate signal must be

applied to the inputs. It then computes an offset that will

nullify offset in the system. The system gain calibration

requires a positive full-scale differential input signal. It then

computes a gain value to nullify gain errors in the system.

Each of these calibrations will take seven tDATA periods to

complete.

Calibration should be performed after power on. It should

also be done after a change in temperature, decimation

ratio, buffer, power supply, voltage reference, or PGA. The

offset DAC will affect offset calibration; therefore, the value

of the offset should be zero before performing a calibration.

At the completion of calibration, the ADC Interrupt bit goes

high, which indicates the calibration is finished and valid

data is available.

ADC DIGITAL FILTER

The Digital Filter can use either the Fast Settling, Sinc2, or

Sinc3 filter, as shown in Figure 10. In addition, the Auto

mode changes the Sinc filter after the input channel or

PGA is changed. When switching to a new channel, it will

use the Fast Settling filter for the next two conversions, the

first of which should be discarded. It will then use the Sinc2

followed by the Sinc3 filter to improve noise performance.

This combines the low-noise advantage of the Sinc3 filter

with the quick response of the Fast Settling Time filter. The

frequency response of each filter is shown in Figure 11.

Fast

FILTER

SETTLING TIME

(Conversion Cycles)(1)

Sinc3

Sinc2

Fast

(1) With synchronized channel changes.

CONVERSION CYCLE

AUTO MODE FILTER SELECTION

FILTER SETTLING TIME

Adjustable Digital Filter

Data Out

Modulator

Fast Settling

Sinc2

Sinc3

Fast

Sinc2

Sinc3

Figure 10. Filter Step Responses

SINC3 FILTER RESPONSE

DATA

−20

−40

−60

−80

−100

−120

345

SINC2 FILTER RESPONSE

DATA

−20

−40

−60

−80

−100

−120

FAST SETTLING FILTER RESPONSE

fDATA

−20

−40

−60

−80

−100

−120

NOTE: f

DATA = Data Output Rate = 1/tDATA

(

−3dB = 0.318 • f

DATA)

(

−3dB = 0.469 • f

DATA)

(

−3dB = 0.262 • f

DATA)

Figure 11. Filter Frequency Responses

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