Datasheet

LTC2413
34
sn2413 2413fs
APPLICATIO S I FOR ATIO
WUU
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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
V
REF
␣ =␣ 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)
0
20 40 60 80 100 120 140 160 180 200 220
NORMAL MODE REJECTION (dB)
2413 F41
0
–20
–40
–60
–80
–100
–120
V
CC
= 5V
REF
+
= 5V
REF
–
= GND
V
INCM
= 2.5V
V
IN(P-P)
= 5V
T
A
= 25°C
MEASURED DATA
CALCULATED DATA