ltc1069-7is8-trpbf Linear Technology Corporation, ltc1069-7is8-trpbf Datasheet - Page 7

• Manufacturer Part Number: ltc1069-7is8-trpbf
• Description: Low Power, 8th Order Progressive Elliptic, Lowpass Filter
• Manufacturer: Linear Technology Corporation

APPLICATIONS
Table 2. Clock Feedthrough
the input pin (4) shorted to the AGND pin and depends on
PC board layout and on the value of the power supplies.
With proper layout techniques the values of the clock
feedthrough are shown on Table 2.
Any parasitic switching transients during the rise and fall
edges of the incoming clock are not part of the clock
feedthrough specifications. Switching transients have fre-
quency contents much higher than the applied clock; their
amplitude strongly depends on scope probing techniques
as well as grounding and power supply bypassing. The
clock feedthrough can be reduced, if bothersome, by
adding a single RC lowpass filter at the output pin (8) of the
LTC1069-1.
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. Most of the wideband
noise frequency contents lie within the filter 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
TYPICAL APPLICATIONS
3.3V
ON
V
5V
5V
SHUTDOWN
S
Single 5V Operation with Power Shutdown
0.47 F
CLOCK FEEDTHROUGH
5V
CMOS LOGIC
160 V
0.1 F
10 V
40 V
U
RMS
RMS
V
RMS
IN
INFORMATION
1
2
3
4
U
AGND
V
NC
V
IN
+
LTC1069-1
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.
V
CLK
OUT
V
NC
U
–
W
8
7
6
5
V
f
750kHz
CLK
OUT
1069-1 TA04
U
5V
0V
0.1 F
0.47 F
supply voltage (see Table 3). The clock feedthrough speci-
fications are not part of the wideband noise.
Table 3. Wideband Noise
Aliasing
Aliasing is an inherent phenomenon of sampled data
systems and it occurs for input frequencies approaching
the sampling frequency. The internal sampling frequency
of the LTC1069-1 is 100 times its cutoff frequency. For
instance, if a 98kHz, 100mV
input of an LTC1069-1 operating with a 100kHz clock, a
2kHz, 28 V
Table 4 shows details.
Table 4. Aliasing (f
f
INPUT FREQUENCY
CLK
3.3V
5V
5V
V
V
96 (or 104)
97 (or 103)
98 (or 102)
985. (or 101.5)
99 (or 101)
99.5 (or 100.5)
(V
/f
IN
S
C
IN
= 100:1, f
1
2
3
4
(kHz)
= 1V
Single 3.3V Supply Operation with Output Buffer
AGND
V
NC
V
+
IN
LTC1069-1
RMS
RMS
)
CUTOFF
V
CLK
WIDEBAND NOISE
OUT
NC
V
–
alias signal will appear at the filter output.
CLK
100 V
108 V
112 V
8
7
6
5
= 1kHz
f
500kHz
= 100kHz)
CLK
(Relative to Input)
OUTPUT LEVEL
RMS
RMS
RMS
3.3V
– 90.0
– 86.0
– 71.0
– 56.0
– 0.21
– 1.1
(dB)
RMS
3.3V
0V
signal is applied at the
LTC1069-1
OUTPUT FREQUENCY
(Aliased Frequency)
+
–
1/2 LT1366
(kHz)
0.1 F
4.0
3.0
2.0
1.5
1.0
0.5
1069-1 TA05
7
V
OUT