LTC1264-7
APPLICATI S I FOR ATIO
Table 9. Maximum VIN vs VS and Clock
POWER SUPPLY
±7.5V
±5V
Single 5V
MAXIMUM fCLK
5.0MHz
4.5MHz
4.0MHz
≥ 3.5MHz
3.0MHz
≥ 3.0MHz
2.0MHz
MAXIMUM VIN
1.6VRMS (fIN ≥ 160kHz)
2.0VRMS (fIN ≥ 160kHz)
2.5VRMS (fIN ≥ 160kHz)
1.6VRMS (fIN ≥ 500kHz)
1.6VRMS (fIN ≥ 100kHz)
0.7VRMS (fIN ≥ 500kHz)
0.5VRMS (fIN ≥ 400kHz)
Transient Response
Aliasing
Aliasing is an inherent phenomenon of sampled data
systems and it occurs when input frequencies close to the
sampling frequency are applied. For the LTC1264-7 case
at 50:1, an input signal whose frequency is in the range of
fCLK ±10%, will be aliased back into the filter’s passband.
If, for instance, an LTC1264-7 operating with a 100kHz
clock and 2kHz cutoff frequency receives a 95kHz 10mV
input signal, a 5kHz 56µVRMS alias signal will appear at its
output. When the LTC1264-7 operates with a clock-to-
cutoff frequency of 25:1, aliasing occurs at twice the clock
frequency. Table 10 shows details.
INPUT = 10kHz ± 3V
fCLK = 2.5MHz
RATIO = 25:1
10µs/DIV
Figure 5.
ts
INPUT
90%
OUTPUT
50%
td
10%
tr
RISE
TIME
(tr)
=
0.36
fCUTOFF
±5%
SETTLING
(TO 1% of
TIME (ts)
OUTPUT)
=
2
fCUTOFF
±5%
TIME DELAY (td) = GROUP
(TO 50% OF OUTPUT)
DELAY
≈
1.15
fCUTOFF
Figure 6.
1164-7 F06
Table 10. Aliasing (fCLK = 100kHz )
INPUT FREQUENCY
(VIN = 1VRMS,
fIN = fCLK ± fOUT)
(kHz)
25:1, fCUTOFF = 4kHz
175 (or 225)
180 (or 220)
185 (or 215)
190 (or 210)
195 (or 205)
50:1, fCUTOFF = 2kHz
75 (or 125)
80 (or 120)
85 (or 115)
90 (or 110)
95 (or 105)
99 (or 101)
OUTPUT LEVEL
(Relative to Input,
0dB = 1VRMS)
(dB)
– 76
– 69
– 62
– 43
–7
– 96
– 90
– 82
– 72
– 45
0
OUTPUT FREQUENCY
(Aliased Frequency
fOUT = ABS [fCLK ± fIN])
(kHz)
25
20
15
10
5
25
20
15
10
5
1
Table 11. Transient Response of LTC Lowpass Filters
LOWPASS FILTER
DELAY
TIME*
(SEC)
RISE SETTLING OVER-
TIME** TIME*** SHOOT
(SEC) (SEC) (%)
LTC1064-3 Bessel
LTC1164-5 Bessel
LTC1164-6 Bessel
0.50/fC 0.34/fC 0.80/fC 0.5
0.43/fC 0.34/fC 0.85/fC 0
0.43/fC 0.34/fC 1.15/fC 1
LTC1264-7 Linear Phase 1.15/fC 0.36/fC 2.05/fC 5
LTC1164-7 Linear Phase
1.20/fC 0.39/fC 2.20/fC
5
LTC1064-7 Linear Phase
1.20/fC 0.39/fC 2.20/fC
5
LTC1164-5 Butterworth
0.80/fC 0.48/fC 2.40/fC 11
LTC1164-6 Elliptic
LTC1064-4 Elliptic
LTC1064-1 Elliptic
0.85/fC 0.54/fC 4.30/fC 18
0.90/fC 0.54/fC 4.50/fC 20
0.85/fC 0.54/fC 6.50/fC 20
* To 50% ±5%, ** 10% to 90% ±5%, *** To 1% ±0.5%
Information furnished by Linear Technology Corporation is believed to be accurate and reliable.
However, no responsibility is assumed for its use. Linear Technology Corporation makes no represen-
tation that the interconnection of its circuits as described herein will not infringe on existing patent rights.
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