COMBOSMARTMETER datasheet(19/60 Pages) TI1

19 / 60 page

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Normalized Frequency (fIN/fMOD)

G001

Max(INP

INN)<

REF

Gain

Full-ScaleRange=

±VREF

Gain

;

REF

Gain

AVDD

0.3

Gain V

MAX_DIFF

> CM > AVSS + 0.3 +

Gain V

MAX_DIFF

ADS131E04

ADS131E06

ADS131E08

www.ti.com

SBAS561A – JUNE 2012 – REVISED APRIL 2013

Input Common-Mode Range

The usable input common-mode range of the analog front-end depends on various parameters, including the

maximum differential input signal, supply voltage, and PGA gain. This range is described in Equation 2:

where:

VMAX_DIFF = maximum differential signal at the PGA input

CM = common-mode range

(2)

For example:

If VDD = 3.3 V, gain = 2, and VMAX_DIFF = 1000 mV,

Then 1.3 V < CM < 2.0 V

Input Differential Dynamic Range

The differential (INP – INN) signal range depends on the analog supply and reference used in the system. This

range is shown in Equation 3.

(3)

For higher dynamic range, a 5-V supply with a 4-V reference (set by the VREF_4V bit of the CONFIG3 register)

can be used to increase the differential dynamic range.

ADC

ΔΣ Modulator

Each ADS131E0x channel has a

ΔΣ ADC. This converter uses a second-order modulator optimized for low-

power applications. The modulator samples the input signal at the rate of [fMOD = fCLK / 2]. As in the case of any

ΔΣ modulator, the ADS131E0x noise is shaped until fMOD / 2, as shown in Figure 22. The on-chip digital

decimation filters also provide antialias filtering. This

ΔΣ converter feature drastically reduces the complexity of

the analog antialiasing filters typically required with nyquist ADCs.

Figure 22. Modulator Noise Spectrum Up To 0.5 × fMOD

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COMBOSMARTMETER Datasheet(PDF) 19 Page - Texas Instruments

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