LTC2410

34

APPLICATIO S I FOR ATIO

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 LTC2410 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 LTC2410 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

range of 5V peak-to-peak. Figures 43 and 44 show mea-

surement results for the LTC2410 normal mode rejection

ratio with a 7.5V peak-to-peak (150% of full scale) input

signal superimposed over the more traditional normal mode

rejection ratio results obtained with a 5V peak-to-peak (full

scale) input signal. In Figure 43, the LTC2410 uses the

and in Figure 44 it uses the internal oscillator with the

rejection performance is maintained with no compromises

in this extreme situation. When operating with large input

signal levels, the user must observe that such signals do

not violate the device absolute maximum ratings.

SYNCHRONIZATION OF MULTIPLE LTC2410s

Since the LTC2410’s absolute accuracy (total unadjusted

error) is 5ppm, applications utilizing multiple synchro-

nized ADCs are possible.

Figure 43. Measured Input Normal Mode Rejection vs Input Frequency with Input Perturbation of 150% Full Scale (60Hz Notch)

Figure 44. Measured Input Normal Mode Rejection vs Input Frequency with Input Perturbation of 150% Full Scale (50Hz Notch)

INPUT FREQUENCY (Hz)

0

15

30

45

60

75

90

105 120 135 150 165 180 195 210 225 240

2410 F43

0

–20

–40

–60

–80

–100

–120

(150% OF FULL SCALE)

INPUT FREQUENCY (Hz)

0

2410 F44

0

–20

–40

–60

–80

–100

–120

(150% OF FULL SCALE)

12.5

25

37.5

50

62.5

75

87.5 100 112.5 125 137.5 150 162.5 175 187.5 200