MSC1211 Datasheet, PDF (29/105 Pages) Texas Instruments – Precision Analog-to-Digital Converter (ADC) and Digital-to-Analog Converters (DACs) with 8051 Microcontroller and Flash Memory

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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 16.
VOLTAGE REFERENCE
The MSC1211/12/13/14 can use either an internal or
external voltage reference. The voltage reference
selection is controlled via ADC Control Register 0
(ADCON0, SFR DCh). The default power-up
configuration for the voltage reference is 2.5V internal.
The internal voltage reference can be selected as either
1.25V or 2.5V. The analog power supply (AV_DD) must be
within the specified range for the selected internal voltage
MSC1211, MSC1212
MSC1213, MSC1214
SBAS323D − JUNE 2004 − REVISED SEPTEMBER 2005
reference. The valid ranges are: V_REF = 2.5 internal
(AV_DD = 3.3V to 5.25V) and V_REF = 1.25 internal
(AV_DD = 2.7V to 5.25V). If the internal V_REF is selected,
then AGND must be connected to REF IN−. The
REFOUT/REF IN+ pin should also have a 0.1µF capacitor
connected to AGND as close as possible to the pin. If the
internal V_REF is not used, then V_REF should be disabled in
ADCON0.
If the external voltage reference is selected, it can be used
as either a single-ended input or differential input, for
ratiometric measures. When using an external reference,
it is important to note that the input current will increase for
V_REF with higher PGA settings and with a higher modulator
frequency. The external voltage reference can be used
over the input range specified in the Electrical
Characteristics section.
0
−20
−40
−60
−80
−100
−120
0
SINC³ FILTER RESPONSE
(−3dB = 0.262 • f_DATA)
1
2
3
4
5
f_DATA
0
−20
−40
−60
−80
−100
−120
0
SINC² FILTER RESPONSE
(−3dB = 0.318 • f_DATA)
1
2
3
4
f_DATA
0
−20
−40
−60
−80
−100
−120
0
FAST SETTLING FILTER RESPONSE
(−3dB = 0.469 • f_DATA)
1
2
3
4
5
f_DATA
NOTE: f_DATA = Normalized Data Output Rate = 1/t_DATA
Figure 16. Filter Frequency Responses
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