LTC1164-6CS Linear Technology, LTC1164-6CS Datasheet - Page 8

• Manufacturer Part Number: LTC1164-6CS
• Description: Low Power 8th Order Pin Selectable Elliptic or Linear Phase Lowpass Filter
• Manufacturer: Linear Technology

PI FU CTIO S
can be used provided that its input common-mode range
is well within the filter’s output swing. Pin 6 is an interme-
diate filter output providing an unspecified 6th order
lowpass filter. Pin 6 should not be loaded.
LTC1164-6
Passband Response
The passband response of the LTC1164-6 is optimized for
a f
occurs from 1Hz to 80% of f
of the LTC1164-6 is optimized for ratio f
100:1, if a ratio of 50:1 is desired, connect a single pole
lowpass RC (f
The RC will make the passband gain response as flat as the
100:1 case. If the RC is omitted, and clock frequencies are
below 500kHz the passband gain will peak by 0.4dB at
90% f
Table 2. Typical Passband Ripple with Single 5V Supply
(f
RC Filter at Pin 9 (See Typical Applications)
PASSBAND
FREQUENCY
% of f
8
A
CLK
PPLICATI
CLK
f
U
CUTOFF
/f
CUTOFF
10
20
30
40
50
60
70
80
90
C
/f
CUTOFF
) = 100:1, GND = 2V, 30kHz, Fixed Single Pole, Lowpass
CUTOFF
U
f
.
CUTOFF
T
Figure 3. Buffer for Filter Output
–3dB
A
ratio of 100:1. Minimum passband ripple
– 0.02
– 0.05
– 0.10
– 0.13
– 0.15
– 0.18
– 0.25
– 0.39
– 2.68
(dB)
= 25 C
0.00
O
1k
= 1kHz
= 2 f
U
U
S
(REFERENCED TO 0dB)
CUTOFF
–
+
PASSBAND GAIN
I FOR ATIO
(14-Lead Dual-In-Line Package)
T
U
CUTOFF
– 0.01
– 0.02
– 0.03
– 0.01
– 0.01
– 0.08
– 0.23
– 2.79
A
(dB)
0.00
0.00
LT1006, f
LT1200, f
= 0 C
) at the output of the filter.
. Athough the passband
C
C
f
CUTOFF
< 5kHz
> 5kHz
1164-6 F03
W
T
A
– 0.01
– 0.02
– 0.01
– 0.05
– 0.18
– 2.74
(dB)
= 25 C
0.00
0.01
0.01
0.01
= 10kHz
CLK
/ f
CUTOFF
T
U
A
– 0.05
– 2.68
(dB)
= 70 C
0.00
0.01
0.01
0.02
0.03
0.05
0.07
0.02
of
External Connection Pins (7, 14)
Pins 7 and 14 should be connected together. In a printed
circuit board the connection should be done under the IC
package through a short trace surrounded by the analog
ground plane.
NC Pin (1, 8, 13)
Pins 1, 8, and 13 are not connected to any internal circuit
point on the device and should preferably be tied to analog
ground.
The gain peaking can approximate a sin / correction for
some applications. (See Typical Performance Characteris-
tics curve, Passband vs Frequency and f
50:1.)
When the LTC1164-6 operates with a single 5V supply and
its cutoff frequency is clock-tuned to 10kHz, an output
single pole RC filter can also help maintain outstanding
passband flatness from 0 C to 70 C. Table 2 shows
details.
Clock Feedthrough
Clock feedthrough is defined as, the RMS value of the clock
frequency and its harmonics that are present at the filter’s
output pin (9). The clock feedthrough is tested with the
input pin (2) grounded and, it 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
in Table 3.
Table 3. Clock Feedthrough
Note: The clock feedthrough at 2.5V supplies is imbedded in the wideband
noise of the filter. (The clock signal is a square wave.)
V
S
2.5V
5V
7.5V
100 V
150 V
60 V
50:1
RMS
RMS
RMS
CLK
200 V
500 V
60 V
100:1
at f
RMS
RMS
RMS
CLK
/ f
C
=