MSC1200 Datasheet, PDF (19/60 Pages) Texas Instruments – Precision Analog-to-Digital Converter (ADC) and Digital-to-Analog Converter (DAC) with 8051 Microcontroller and Flash Memory

0
–20
–40
–60
–80
–100
–120
0
0
–20
–40
–60
–80
–100
–120
0
0
–20
–40
–60
–80
–100
–120
0
SINC³ FILTER RESPONSE
(–3dB = 0.262 • f_DATA)
1
2
3
4
5
f_DATA
SINC² FILTER RESPONSE
(–3dB = 0.318 • f_DATA)
1
2
3
4
5
f_DATA
FAST SETTLING FILTER RESPONSE
(–3dB = 0.469 • f_DATA)
1
2
3
4
5
f_DATA
NOTE: f_DATA = Data Output Rate = 1/t_DATA
FIGURE 9. Filter Frequency Responses.
VOLTAGE REFERENCE
The MSC1200 can use either an internal or external voltage
reference. The voltage reference selection is controlled via
ADC Control Register 0 (ADCON0, SFR DC_H). 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 reference.
The valid ranges are: V_REF = 2.5 internal (AV_DD = 4.1V 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
REFIN–. The REFOUT/REFIN+ 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 of 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.
IDAC
The 8-bit IDAC in the MSC1200 can be used to provide a
current source that can be used for ratiometric measure-
ments. The IDAC operates from its own voltage reference
and is not dependent on the ADC voltage reference. The full-
scale output current of the IDAC is approximately 1mA. The
equation for the IDAC output current is:
IDACOUT = IDAC • 3.6µA
RESET
Taking the RST pin HIGH will stop the operation of the
device, and taking the RST pin LOW will initiate a reset. The
device can also be reset by the power on reset circuitry,
digital brownout Reset, or software reset. The timing of the
reset operation is shown in the Electrical Characteristics
section.
If the P1.0/PROG pin is unconnected or tied HIGH, the
device will enter User Application mode on reset. If P1.0/
PROG is tied LOW during reset, the device will enter Serial
Programming mode.
POWER ON RESET
The on-chip Power On Reset (POR) circuitry releases the
device from reset at approximately DVDD = 2.0V. The POR
accommodates power-supply ramp rates as slow as
1V/10ms. To ensure proper operation, the power supply
should ramp monotonically. Note that, as the device is
released from reset and program execution begins, the
device current consumption may increase, which may result
in a power-supply voltage drop. If the power supply ramps at
a slower rate, is not monotonic, or a brownout condition
occurs (where the supply does not drop below the 2.0V
threshold), then improper device operation may occur. The
on-chip Brownout Reset (BOR) may provide benefit in these
conditions. A POR circuit is shown in Figure 10.
DV_DD
0.1µF
1MΩ
MSC1200
10kΩ _{5 RST}
FIGURE 10. Typical Reset Circuit.
MSC1200
19
SBAS289E
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