LTC1069-1C View Datasheet(PDF) - Linear Technology
Part Name
Description
Manufacturer
LTC1069-1C Datasheet PDF : 8 Pages
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LTC1069-1
APPLICATIONS INFORMATION
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.
Table 2. Clock Feedthrough
VS
CLOCK FEEDTHROUGH
3.3V
10µVRMS
5V
40µVRMS
±5V
160µVRMS
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
supply voltage (see Table 3). The clock feedthrough speci-
fications are not part of the wideband noise.
Table 3. Wideband Noise
VS
WIDEBAND NOISE
3.3V
100µVRMS
5V
108µVRMS
±5V
112µVRMS
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, 100mVRMS signal is applied at the
input of an LTC1069-1 operating with a 100kHz clock, a
2kHz, 28µVRMS alias signal will appear at the filter output.
Table 4 shows details.
Table 4. Aliasing (fCLK = 100kHz)
INPUT FREQUENCY
(VIN = 1VRMS)
(kHz)
OUTPUT LEVEL
(Relative to Input)
(dB)
fCLK/fC = 100:1, fCUTOFF = 1kHz
96 (or 104)
– 90.0
97 (or 103)
– 86.0
98 (or 102)
– 71.0
985. (or 101.5)
– 56.0
99 (or 101)
– 1.1
99.5 (or 100.5)
– 0.21
OUTPUT FREQUENCY
(Aliased Frequency)
(kHz)
4.0
3.0
2.0
1.5
1.0
0.5
TYPICAL APPLICATIONS
Single 5V Operation with Power Shutdown
SHUTDOWN
ON
5V
CMOS LOGIC
0.47µF
0.1µF
1 AGND VOUT 8
2 V+
V– 7
3
LTC1069-1
NC
NC
6
VOUT
VIN 4 VIN
CLK 5
fCLK ≤
750kHz
5V
0V
1069-1 TA04
Single 3.3V Supply Operation with Output Buffer
3.3V
0.47µF
0.1µF
1 AGND VOUT 8
2 V+
V– 7
3
LTC1069-1
NC
NC
6
VIN 4 VIN
CLK 5
fCLK
500kHz
3.3V
0V
0.1µF
+
1/2 LT1366
–
VOUT
1069-1 TA05
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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