LTC2203/LTC2202
APPLICATIONS INFORMATION
Digital Output Randomizer
Interference from the ADC digital outputs is sometimes
unavoidable. Interference from the digital outputs may be
from capacitive or inductive coupling or coupling through
the ground plane. Even a tiny coupling factor can result in
discernible unwanted tones in the ADC output spectrum.
By randomizing the digital output before it is transmitted
off chip, these unwanted tones can be randomized, trading
a slight increase in the noise floor for a large reduction
in unwanted tone amplitude.
The digital output is “Randomized” by applying an exclu-
sive-OR logic operation between the LSB and all other data
output bits. To decode, the reverse operation is applied;
that is, an exclusive-OR operation is applied between the
LSB and all other bits. The LSB, OF and CLKOUT output
are not affected. The output Randomizer function is active
when the RAND pin is high.
LTC2203/LTC2202
CLKOUT
CLKOUT
OF
OF
D15
D15/D0
D14
D14/D0
•
•
•
D2
D2/D0
D1
D1/D0
RAND = HIGH,
SCRAMBLE
ENABLED
RAND
D0
D0
22032 F11
Figure 10. Functional Equivalent of Digital Output Randomizer
22032fd
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