LTC1264CS Linear Technology, LTC1264CS Datasheet - Page 7

• Manufacturer Part Number: LTC1264CS
• Description: High Speed/ Quad Universal Filter Building Block
• Manufacturer: Linear Technology

W
optimum mode for high Q designs with f
f
Please refer to the Maximum Frequency of Operation
paragraph under Applications Information for a guide to
the use of capacitor C
V
CENTER
V
IN
IN
ODES OF OPERATIO
Figure 4. Mode 1, 2nd Order Filter Providing Notch,
Bandpass and Lowpass Outputs
Figure 5. Mode 1b, 2nd Order Filter Providing Notch,
Bandpass and Lowpass Outputs
R1
R1
) ratios greater than 20:1.
AGND
AGND
–
+
–
+
R3
R2
R3
R2
C
C
NOTE: R5 5k
f
Q =
H
C
i
OLP
=
.
f
R3
R2
f
Q =
H
CLK
i
20
OLP
= –
=
1/4 LTC1264
f
R3
R2
CLK
; f
20
R6
(R6 + R5)
R2
R1
N
= H
1/4 LTC1264
N
O
; H
+
= f
; f
+
R6
C
ON
ON
R6 + R5
C
O
i
= f
R6
= –
(R6 + R5)
–
–
; H
i
S
; f
S
R2
R1
R6
n
ON
R5
= f
; H
U
= –
O
OBP
; f
CLK
R2
R1
n
= –
= f
; H
O
to f
OBP
R3
R1
BP
BP
= –
CUTOFF
R3
R1
1264 F04
1264 F05
(or
LP
LP
Mode 3
In Mode 3, the ratio of the external clock frequency to the
center frequency of each 2nd order section can be
adjusted above or below 20:1. Figure 6 illustrates Mode 3,
the classical state variable configuration, providing high-
pass, bandpass, and lowpass 2nd order filter functions.
Mode 3 is slower than Mode 1. Mode 3 can be used to
make high order all-pole bandpass, lowpass, and high-
pass filters.
Please refer to the Maximum Frequency of Operation
paragraph under Applications Information for a guide to
the use of capacitor C
Mode 2
Mode 2 is a combination of Mode 1 and Mode 3, shown in
Figure 7. With Mode 2, the clock-to-center frequency ratio,
f
2 is that it provides less sensitivity to resistor tolerances
than does Mode 3. As in Mode 1, Mode 2 has a notch
output which depends on the clock frequency, and the
notch frequency is therefore less than the center fre-
quency, f
Please refer to the Maximum Frequency of Operation
paragraph under Applications Information for a guide to
the use of capacitor C
CLK
V
IN
/f
O
AGND
R1
, is always less than 20:1. The advantage of Mode
Figure 6. Mode 3, 2nd Order Section Providing
Highpass, Bandpass and Lowpass Outputs
O
.
H
–
+
f
i
OHP
=
f
CLK
R4
R3
R2
20
= –
; f
R2
R1
C
C
O
.
.
; H
= f
OBP
i
1/4 LTC1264
R2
R4
= –
HP
; Q = 1.005
+
R3
R1
C
C
1 –
–
S
6.42•R4
1
R3
R2
R3
R2
R4
LTC1264
;
H
OLP
1 –
BP
= –
6.42•R4
1
R3
1264 F06
R4
R1
7
LP