LTC1069-6

8

10696fa

Wideband Noise

The wideband noise of the filter 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 filter’s passband. The

wideband noise cannot be reduced by adding post filtering.

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 specifications

are not part of the wideband noise.

Table 3. Wideband Noise

WIDEBAND NOISE

3.3V

5V

±5V

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

the input of an LTC1069-6 operating with a 50kHz clock,

output. Table 4 shows details.

INPUT FREQUENCY

(kHz)

OUTPUT LEVEL

(Relative to Input)

(dB)

OUTPUT FREQUENCY

(Aliased Frequency)

(kHz)

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