MSC1210 datasheet(23/83 Pages) TI

23 / 83 page

MSC1210

SBAS203F − MARCH 2002 − REVISED NOVEMBER 2004

www.ti.com

IN3

IN4

IN5

IN6

IN0

IN1

IN2

IN7

IN CO M

Burnout Detect

Current Source

Burnout Detect

Current Sink

AGND

Temperature Sensor

• I

In+

−

Figure 12. Input Multiplexer Configuration

BURNOUT DETECT

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

control configuration register (ADCON0 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. This allows for the detection of an

open circuit (full-scale reading) or short circuit (small

differential reading) on the selected input differential pair.

Buffer should be on for sensor burnout detection.

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 MSC1210 without the buffer is

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

bit in the ADC control register (ADCON0 DCh).

ANALOG INPUT

When the buffer is not selected, the input impedance of the

analog input changes with ACLK clock frequency (ACLK

F6h) and gain (PGA). The relationship is:

IN Impedance(W) +

ACLK Frequency

@ 7MW

PGA

where ACLK frequency

OSC

(ACLK

)1)

and

modclk

+ f

MOD +

ACLK

NOTE: The input impedance for PGA = 128 is the same as that for

PGA = 64 (

that is,

Figure 13 shows the basic input structure of the MSC1210.

switch

(3k typical)

AGND

High Impedance

>1G

Ω

PGA

SAMP

1, 2, 4

modclk

2 * modclk

4 * modclk

8 * modclk

64, 128

16 * modclk

PGA

9pF

18pF

4to128

36pF

Sampling

Frequency = fSAMP

(9pF typical)

Figure 13. Analog Input Structure

MODULATOR

The modulator is a single-loop 2nd-order system. The

modulator runs at a clock speed (fMOD) that is derived from

the CLK using the value in the Analog Clock (ACLK)

Data Rate

MOD

Decimation Ratio

where f

MOD +

OSC

(ACLK

)1) @ 64

MSC1210 Datasheet(PDF) 23 Page - Texas Instruments

MSC1210 Datasheet(HTML) 23 Page - Texas Instruments

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