MCP3912 datasheet(31/82 Pages) MICROCHIP

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DS20005348A-page 31

MCP3912

5.3.2

MODULATOR INPUT RANGE AND

SATURATION POINT

For a specified voltage reference value of 1.2V, the

specified differential input range is ±600 mV. The input

range is proportional to VREF and scales according to

the VREF voltage. This range ensures the stability of the

modulator over amplitude and frequency. Outside of

this range, the modulator is still functional; however, its

stability is no longer ensured and therefore it is not

recommended to exceed this limit. The saturation point

for the modulator is VREF/1.5, since the transfer

function of the ADC includes a gain of 1.5 by default

(independent from the PGA setting). See Section 5.5

“ADC Output Coding”

5.3.3

BOOST SETTINGS

The delta-sigma modulators include a programmable

biasing circuit in order to further adjust the power

consumption to the sampling speed applied through

the MCLK. This can be programmed through the

BOOST<1:0> bits, which are applied to all channels

simultaneously.

The maximum achievable analog master clock speed

(AMCLK), the maximum sampling frequency (DMCLK)

and the maximum achievable data rate (DRCLK),

highly depend on BOOST<1:0> and PGA_CHn<2:0>

settings. Table 5-2 specifies the maximum AMCLK

possible to keep optimal accuracy in the function of

BOOST<1:0> and PGA_CHn<2:0> settings.

TABLE 5-2:

MAXIMUM AMCLK LIMITS AS A FUNCTION OF BOOST AND PGA GAIN

Conditions

VDD = 3.0V to 3.6V,

TA from -40°C to +125°C

VDD = 2.7V to 3.6V,

TA from -40°C to +125°C

Boost

Gain

Maximum AMCLK

(MHz)

(SINAD within -3 dB

from its maximum)

Maximum AMCLK

(MHz)

(SINAD within -5 dB

from its maximum)

Maximum AMCLK

(MHz)

(SINAD within -3 dB

from its maximum)

Maximum AMCLK

(MHz)

(SINAD within -5 dB

from its maximum)

0.5x

0.66x

6.4

7.3

6.4

7.3

11.4

10.6

0.5x

0.66x

6.4

7.3

6.4

7.3

11.4

10.6

13.3

14.5

0.5x

2.9

0.66x

6.4

10.7

9.4

10.7

0.5x

2.9

0.66x

7.3

6.4

7.3

11.4

12.3

8.9

11.4

0.5x

2.9

0.66x

6.4

7.3

6.4

7.3

11.4

9.4

10.6

13.3

8.9

11.4

0.5x

2.9

0.66x

7.3

10.6

12.3

9.4

10,6

13.3

11.4

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