LTC1068IG Linear Technology, LTC1068IG Datasheet - Page 12

• Manufacturer Part Number: LTC1068IG
• Description: IC FILTR BUILDNG BLK QUAD 28SSOP
• Manufacturer: Linear Technology

Specifications of LTC1068IG

• Filter Type: Universal Switched Capacitor
• Frequency - Cutoff Or Center: 50kHz
• Number Of Filters: 4
• Max-order: 8th
• Voltage - Supply: 3.14 V ~ 11 V, ±3.14 V ~ 5.5 V
• Mounting Type: Surface Mount
• Package / Case: 28-SSOP
• Lead Free Status / RoHS Status: Contains lead / RoHS non-compliant

W
LTC1068 Series
Mode 3
In Mode 3, the ratio of the external clock frequency to the
center frequency of each 2nd order section can be ad-
justed above or below the parts nominal ratio. Figure 6
illustrates Mode 3, the classical state variable configura-
tion, providing highpass, 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 highpass filters.
Please refer to the Operating Limits paragraph under Appli-
cations 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
advantage of Mode 2 is that it provides less sensitivity to
resistor tolerances than does Mode 3. Mode 2 has a
highpass notch output where the notch frequency de-
pends solely on the clock frequency and is therefore less
than the center frequency, f
Please refer to the Operating Limits paragraph under Appli-
cations Information for a guide to the use of capacitor C
12
MODES OF
CLK
V
IN
/f
Figure 5. Mode 1b, 2nd Order Filter Providing Notch,
Bandpass and Lowpass Outputs
O
R1
, is always less than the part’s nominal ratio. The
AGND
f
Q =
H
–
+
O
OLP
=
R3
R2
RATIO
R3
R2
f
= –
CLK
√
OPERATION
C
(R6 + R5)
R2
R1
C
√
R6
(R6 + R5)
(
R6 + R5
R6
R6
; H
R6
O
N
ON
)
.
; f
+
n
= –
= f
Σ
O
R2
R1
–
S
; H
R5
OBP
U
DEVICE
LTC1068
LTC1068-200
LTC1068-50
LTC1068-25
= –
R3
R1
BP
RATIO
1068 F05
100
200
50
25
C
LP
.
C
.
V
IN
V
IN
H
H
Q = 1.005
f
OBP
OHPN
O
Figure 7. Mode 2, 2nd Order Filter Providing Highpass
Notch, Bandpass and Lowpass Outputs
=
AGND
R1
RATIO
= –
AGND
R1
f
= –
CLK
Figure 6. Mode 3, 2nd Order Section Providing
Highpass, Bandpass and Lowpass Outputs
R3
R1
( ) √
R3
R2
R2
R1
√
(
1 +
(AC GAIN, f >> f
1–
1 +
f
(RATIO)(0.32)(R4)
H
–
+
O
DEVICE
LTC1068
LTC1068-200
LTC1068-50
LTC1068-25
R2
R4
OHP
=
–
+
R2
R4
; f
RATIO
R4
R3
R2
f
n
CLK
= –
1
=
R3
R2
R4
R3
(
RATIO
1–
R2
R1
f
CLK
√
(RATIO)(0.32)(R4)
O
; H
R2
R4
); H
RATIO
OBP
; Q = 1.005
100
200
OHPN
50
25
1/4 LTC1068
)
1
R3
= –
; H
HP
= –
HPN
+
R3
R1
OLP
C
+
C
Σ
C
R2
R1
( )
C
(
= –
Σ
R3
R2
1 –
–
S
)
(
–
R2
R1
1 +
S
(RATIO)(0.32)(R4)
√
1
R2
R4
R2
R4
(
1 +
1
)
(
1
DEVICE
LTC1068
LTC1068-200
LTC1068-50
LTC1068-25
R3
1 –
R2
R4
(DC GAIN)
(RATIO)(0.32)(R4)
)
BP
BP
1
)
R3
; H
1068 F06
RATIO
OLP
1068 F07
100
200
50
25
= –
1068fb
LP
)
LP
R4
R1