MSC1202Y2RHHT datasheet(23/92 Pages) TI

23 / 92 page

MSC1200

MSC1201

MSC1202

SBAS317E − APRIL 2004 − REVISED MAY 2006

www.ti.com

ADC INPUT MULTIPLEXER

The input multiplexer provides for any combination of

differential inputs to be selected as the input channel, as

shown in Figure 8. For example, if AIN0 is selected as the

positive differential input channel, then any other channel

can be selected as the negative differential input channel.

With this method, it is possible to have up to six fully

differential input channels. It is also possible to switch the

polarity of the differential input pair to negate any offset

voltages. In addition, current sources are supplied that will

source or sink current to detect open or short circuits on the

pins.

AIN3

AIN4

AIN5

AIN0

AIN1

AIN2

AINCOM

NOTE: (1) For MSC1201/MSC1202, AIN6 and AIN7 are tied to REFIN

−.

BurnoutDetect(2

µA)

BurnoutDetect(2

µA)

AGND

Buffer

Temperature Sensor

• I

In+

−

AIN6(1)

AIN7(1)

Figure 8. Input Multiplexer Configuration

TEMPERATURE SENSOR

On-chip diodes provide temperature sensing capability.

When the configuration register for the input mux is set to

all 1s, the diodes are connected to the inputs of the ADC.

All other channels are open. The internal device power

dissipation affects the temperature sensor reading. It is

recommended that the internal buffer be enabled for

temperature sensor measurements.

BURNOUT DETECT

When the Burnout Detect (BOD) bit is set in the ADC

control configuration register (ADCON0, SFR DCh), two

current sources are enabled. The current source on the

positive input channel sources approximately 2

µA of

current. The current source on the negative input channel

sinks approximately 2

µA. These current sources allow for

the detection of an open circuit (full-scale reading) or short

circuit (small differential reading) on the selected input

differential pair. The buffer should be on for sensor burnout

detection.

ADC INPUT BUFFER

The analog input impedance is always high, regardless of

PGA setting (when the buffer is enabled). With the buffer

enabled, the input voltage range is reduced and the analog

power-supply current is higher. If the limitation of input

voltage range is acceptable, then the buffer is always

preferred.

The input impedance of the MSC120x without the buffer is

Ω/PGA. The buffer is controlled by the state of the BUF

bit in the ADC control register (ADCON0, SFR DCh).

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