LTC1164-7 Linear Technology, LTC1164-7 Datasheet - Page 10

• Manufacturer Part Number: LTC1164-7
• Description: Low Power/ Linear Phase 8th Order Lowpass Filter
• Manufacturer: Linear Technology

PI FU CTIO S
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 8.
LTC1164-7
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.
A
Table 8. Clock Feedthrough
Note: The clock feedthrough at Single 5V is imbedded in the
wideband noise of the filter. The clock waveform is a square wave.
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, if bothersome, can be greatly reduced
by adding a simple R/C lowpass network at the output of
the filter pin (9). This R/C will completely eliminate any
switching transients.
Wideband Noise
The wideband noise of the filter is the total RMS value of
the device’s noise spectral density and it is used to
determine the operating signal-to-noise ratio. Most of its
frequency contents lie within the filter’s passband and
cannot be reduced with post filtering. For instance, the
10
PPLICATI
V
Single 5V
U
S
5V
7.5V
U
O
100 V
120 V
70 V
U
U
50:1
S
RMS
RMS
RMS
I FOR ATIO
U
W
200 V
500 V
70 V
100:1
RMS
RMS
RMS
U
LTC1164-7 wideband noise at 5V supply is 105 V
95 V
the filter’s cutoff frequency. The total wideband noise
( V
The clock feedthrough specifications are not part of the
wideband noise.
Speed Limitations
The LT1164-7 optimizes AC performance vs power con-
sumption. 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.
NC Pins (1, 8, 13)
Pins 1, 8 and 13 are not connected to any internal circuit
point on the device and should be preferably tied to analog
ground.
Table 9. Maximum V
Table 10. Transient Response of LTC Lowpass Filters
LOWPASS FILTER
LTC1064-3 Bessel
LTC1164-5 Bessel
LTC1164-6 Bessel
LTC1264-7 Linear Phase
LTC1164-7 Linear Phase
LTC1064-7 Linear Phase
LTC1164-5 Butterworth
LTC1164-6 Elliptic
LTC1064-4 Elliptic
LTC1064-1 Elliptic
* To 50% 5%, ** 10% to 90% 5%, *** To 1% 0.5%
POWER SUPPLY
Single 5V
RMS
7.5V
5V
RMS
) is nearly independent of the value of the clock.
of which have frequency contents from DC up to
IN
MAXIMUM f
vs V
1MHz
1MHz
1MHz
S
0.50/f
0.43/f
0.43/f
DELAY
1.15/f
1.20/f
1.20/f
0.80/f
0.85/f
0.90/f
0.85/f
TIME*
(SEC)
and Clock
CLK
C
C
C
C
C
C
C
C
C
C
TIME**
0.34/f
0.34/f
0.34/f
0.36/f
0.39/f
0.39/f
0.48/f
0.54/f
0.54/f
0.54/f
(SEC)
RISE
2.0V
0.7V
1.4V
0.5V
0.5V
C
C
C
C
C
C
C
C
C
C
MAXIMUM V
SETTLING OVER-
TIME*** SHOOT
RMS
RMS
RMS
RMS
RMS
0.80/f
0.85/f
6.50/f
1.15/f
2.05/f
2.20/f
2.20/f
2.40/f
4.30/f
4.50/f
(SEC)
(f
(f
(f
(f
(f
IN
IN
IN
IN
IN
C
C
C
C
C
C
C
C
C
C
> 20kHz)
> 250kHz)
> 20kHz)
> 100kHz)
> 100kHz)
IN
(%)
0.5
11
18
20
20
RMS
0
1
5
5
5
,