SC1200 datasheet(19/60 Pages) TI

19 / 60 page

MSC1200

SBAS289E

www.ti.com

FIGURE 9. Filter Frequency Responses.

SINC3 FILTER RESPONSE

DATA

–20

–40

–60

–80

–100

–120

2345

SINC2 FILTER RESPONSE

DATA

–20

–40

–60

–80

–100

–120

FAST SETTLING FILTER RESPONSE

DATA

–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)

If the internal VREF is not used, then VREF 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 VREF 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 • 3.6

µA

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.

FIGURE 10. Typical Reset Circuit.

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 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 (AVDD) must be within the

specified range for the selected internal voltage reference.

The valid ranges are: VREF = 2.5 internal (AVDD = 4.1V to

5.25V) and VREF = 1.25 internal (AVDD = 2.7V to 5.25V). If the

internal VREF is selected then AGND must be connected to

REFIN–. The REFOUT/REFIN+ pin should also have a 0.1

µF

capacitor connected to AGND as close as possible to the pin.

MSC1200

RST

Ω

0.1

µF

10k

Ω

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