Datasheet

LTC1069-6
8
10696fa
Wideband Noise
The wideband noise of the fi lter is the total RMS value
of the device’s noise spectral density and determines the
operating signal-to-noise ratio. The frequency contents
of the wideband noise lie within the fi lter’s passband. The
wideband noise cannot be reduced by adding post fi ltering.
The total wideband noise is nearly independent of the
clock frequency and depends slightly on the power supply
voltage (see Table 3). The clock feedthrough specifi cations
are not part of the wideband noise.
Table 3. Wideband Noise
V
S
WIDEBAND NOISE
3.3V 118μV
RMS
5V 123μV
RMS
±5V 127μV
RMS
APPLICATIONS INFORMATION
Aliasing
Aliasing is an inherent phenomenon of sampled data
systems and occurs for input frequencies approaching
the sampling frequency. The internal sampling frequency
of the LTC1069-6 is 100 times its cutoff frequency. For
instance, if a 98.5kHz, 100mV
RMS
signal is applied at
the input of an LTC1069-6 operating with a 50kHz clock,
a 1.5kHz, 484μV
RMS
alias signal will appear at the fi lter
output. Table 4 shows details.
Table 4. Aliasing (f
CLK
= 50kHz)
INPUT FREQUENCY
(V
IN
= 1V
RMS
)
(kHz)
OUTPUT LEVEL
(Relative to Input)
(dB)
OUTPUT FREQUENCY
(Aliased Frequency)
(kHz)
f
CLK
/f
C
= 50:1, f
CUTOFF
= 1kHz
96 (or 104) –78.3 4.0
97 (or 103) –70.4 3.0
98 (or 102) – 80.6 2.0
98.5 (or 101.5) –46.3 1.5
99 (or 101) –2.8 1.0
99.5 (or 100.5) –1.38 0.5