LTC2413 datasheet(34/44 Pages) LINER

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LTC2413

sn2413 2413fs

APPLICATIO S I FOR ATIO

The user can expect to achieve in practice this level of

performance using the internal oscillator, as it is demon-

strated by Figure 41. Typical measured values of the

normal mode rejection of the LTC2413 operating with the

internal oscillator are shown in Figure 41 superimposed

over the theoretical calculated curve.

As a result of these remarkable normal mode specifica-

tions, minimal (if any) antialias filtering is required in front

of the LTC2413. If passive RC components are placed in

front of the LTC2413, the input dynamic current should be

considered (see Input Current section). In cases where

large effective RC time constants are used, an external

buffer amplifier may be required to minimize the effects of

dynamic input current.

Traditional high order delta-sigma modulators, while pro-

viding very good linearity and resolution, suffer from po-

tential instabilities at large input signal levels. The propri-

etary architecture used for the LTC2413 third order modu-

lator resolves this problem and guarantees a predictable

stable behavior at input signal levels of up to 150% of full

scale. In many industrial applications, it is not uncommon

to have to measure microvolt level signals superimposed

over volt level perturbations and LTC2413 is eminently

suited for such tasks. When the perturbation is differential,

the specification of interest is the normal mode rejection

for large input signal levels. With a reference voltage

VREF = 5V, the LTC2413 has a full-scale differential input

Figure 41. Input Normal Mode Rejection vs Input

Frequency with Input Perturbation of 100% of Full Scale

INPUT FREQUENCY (Hz)

100

120

140

160

180

200

220

2413 F41

–20

–40

–60

–80

–100

–120

VCC = 5V

REF+ = 5V

REF – = GND

VINCM = 2.5V

VIN(P-P) = 5V

TA = 25°C

MEASURED DATA

CALCULATED DATA

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