Datasheet

12
LTC1064-7
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S
A
O
PP
L
IC
AT
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WU
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I FOR ATIO
Speed Limitations
To avoid op amp slew rate limiting at maximum clock
frequencies, the signal amplitude should be kept below a
specified level as shown in Table 9.
Table 9. Maximum V
IN
vs V
S
and Clock
POWER SUPPLY MAXIMUM f
CLK
MAXIMUM V
IN
±7.5V 5.0MHz 1.8V
RMS
(f
IN
> 80kHz)
4.5MHz 2.3V
RMS
(f
IN
> 80kHz)
4.0MHz 2.7V
RMS
(f
IN
> 80kHz)
≥ 3.5MHz 1.4V
RMS
(f
IN
> 500kHz)
±5V 3.5MHz 1.6V
RMS
(f
IN
> 80kHz)
≥ 3.0MHz 0.7V
RMS
(f
IN
> 400kHz)
Single 5V 2.0MHz 0.5V
RMS
(f
IN
> 250kHz)
Table 10. Transient Response of LTC Lowpass Filters
DELAY RISE SETTLING OVER-
TIME* TIME** TIME*** SHOOT
LOWPASS FILTER (SEC) (SEC) (SEC) (%)
LTC1064-3 Bessel 0.50/f
C
0.34/f
C
0.80/f
C
0.5
LTC1164-5 Bessel 0.43/f
C
0.34/f
C
0.85/f
C
0
LTC1164-6 Bessel 0.43/f
C
0.34/f
C
1.15/f
C
1
LTC1264-7 Linear Phase 1.15/f
C
0.36/f
C
2.05/f
C
5
LTC1164-7 Linear Phase 1.20/f
C
0.39/f
C
2.2/f
C
5
LTC1064-7 Linear Phase 1.20/f
C
0.39/f
C
2.2/f
C
5
LTC1164-5 Butterworth 0.80/f
C
0.48/f
C
2.4/f
C
11
LTC1164-6 Elliptic 0.85/f
C
0.54/f
C
4.3/f
C
18
LTC1064-4 Elliptic 0.90/f
C
0.54/f
C
4.5/f
C
20
LTC1064-1 Elliptic 0.85/f
C
0.54/f
C
6.5/f
C
20
* To 50% ±5%, ** 10% to 90% ±5%, *** To 1% ±0.5%
Table 11. Aliasing (f
CLK
= 100kHz)
INPUT FREQUENCY OUTPUT LEVEL OUTPUT FREQUENCY
(V
IN
= 1V
RMS
, (Relative to Input, (Aliased Frequency
f
IN
= f
CLK
± f
OUT
) 0dB = 1V
RMS
)f
OUT
= ABS [f
CLK
± f
IN
])
(kHz) (dB) (kHz)
50:1, f
CUTOFF
= 2kHz
190 (or 210) –76.1 10.0
195 (or 205) – 51.9 5.0
196 (or 204) – 36.3 4.0
197 (or 203) – 18.4 3.0
198 (or 202) – 3.0 2.0
199.5 (or 200.5) – 0.2 0.5
100:1, f
CUTOFF
= 1kHz
97 (or 103) –74.2 3.0
97.5 (or 102.5) – 53.2 2.5
98 (or 102) –36.9 2.0
98.5 (or 101.5) – 19.6 1.5
99 (or 101) – 5.2 1.0
99.5 (or 100.5) – 0.7 0.5
Transient Response
2V/DIV
50µs/DIV
1064-7 F05
V
S
= ± 7.5V, f
IN
= 2kHz ± 3V
f
CLK
= 1MHz, RATIO = 50:1
Figure 6.
INPUT
90%
50%
10%
OUTPUT
t
r
t
d
t
s
1064-7 F06
RISE TIME (t
r
) = ±5%
0.39
f
CUTOFF
SETTLING TIME (t
s
) = ±5%
(TO 1% of OUTPUT)
2.2
f
CUTOFF
DELAY TIME (t
d
) = GROUP DELAY ≈
(TO 50% OF OUTPUT)
1.2
f
CUTOFF
Figure 5.
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 LTC1064-7 case
at 100:1, an input signal whose frequency is in the range
of f
CLK
±3%, will be aliased back into the filter’s passband.
If, for instance, an LTC1064-7 operating with a 100kHz
clock and 1kHz cutoff frequency receives a 98kHz, 10mV
input signal, a 2kHz, 143µV
RMS
alias signal will appear at
its output. When the LTC1064-7 operates with a clock-to-
cutoff frequency of 50:1, aliasing occurs at twice the clock
frequency. Table 11 shows details.