LTC1562CG#PBF Linear Technology, LTC1562CG#PBF Datasheet - Page 26

• Manufacturer Part Number: LTC1562CG#PBF
• Description: IC FILTER UNIV RC QUAD LN 20SSOP
• Manufacturer: Linear Technology

Specifications of LTC1562CG#PBF

• Filter Type: Universal, Continuous-Time
• Frequency - Cutoff Or Center: 150kHz
• Number Of Filters: 4
• Max-order: 8th
• Voltage - Supply: 4.75 V ~ 10.5 V, ±4.75 V ~ 5.25 V
• Mounting Type: Surface Mount
• Package / Case: 20-SSOP
• Lead Free Status / RoHS Status: Lead free / RoHS Compliant

LTC1562
Construction and Instrumentation Cautions
100dB rejections at hundreds of kilohertz require electri-
cally clean, compact construction, with good grounding
and supply decoupling, and minimal parasitic capaci-
tances in critical paths (such as Operational Filter block
INV inputs). In a circuit with 5k resistances trying for
100dB rejection at 100kHz, a stray coupling of 0.003pF
around the signal path can preclude the 100dB. (By
comparison, the stray capacitance between two adjacent
pins of an IC can be 1pF or more.) Also, high quality supply
bypass capacitors of 0.1 F near the chip provide good
decoupling from a clean, low inductance power source.
But several inches of wire (i.e., a few microhenrys of
inductance) from the power supplies, unless decoupled
TYPICAL APPLICATIONS
26
V
V
IN1
IN2
5V
SCHEMATIC INCLUDES PIN NUMBERS FOR 20-PIN PACKAGE.
PINS 4, 7, 14, 17 (NOT SHOWN) ALSO CONNECT TO V
R
R
IN1A
IN1A
R
R
IN1B
IN1B
C
C
IN1
IN1
Dual 5th Order Lowpass “Elliptic” Filter
0.1 F
R
R21
R21
R
Q1
Q1
f
C
100k
75k
50k
(Hz)
10
1
2
3
5
6
8
9
INVB
V1B
V2B
V
SHDN
V2A
V1A
INVA
R
8.06k
16.9k
5.9k
+
IN1A
LTC1562
U
C
C
IN2
IN2
R
15.4k
35.7k
7.5k
–
IN1B
AGND
INVD
INVC
V1C
V2C
V2D
V1D
(Advanced)
V
–
20
19
18
16
15
13
12
11
680pF
560pF
390pF
C
IN1
R
R
R
R22
R22
R
IN2
IN2
Q2
Q2
36.5k
56.2k
R
28k
Q1
1562 TA15a
0.1 F
by substantial capacitance ( 10 F) near the chip, can
cause a high-Q LC resonance in the hundreds of kHz in the
chip’s supplies or ground reference, impairing stopband
rejection and other specifications at those frequencies. In
demanding filter circuits we have often found that a
compact, carefully laid out printed circuit board with good
ground plane makes a difference of 20dB in both stopband
rejection and distortion performance. Highly selective
circuits can even exhibit these issues at frequencies well
below 100kHz. Finally, equipment to measure filter perfor-
mance can itself introduce distortion or noise floors;
checking for these limits with a wire replacing the filter is
a prudent routine procedure.
13.3k
30.1k
R21
7.5k
V
– 5V
V
OUT1
OUT2
6.34k
11.3k
25.5k
R
IN2
68pF
68pF
68pF
C
IN2
–100
–120
–20
– 40
– 60
– 80
20
0
10
9.31k
12.7k
18.7k
f
R
C
Q2
= 100kHz
Amplitude Response
FREQUENCY (kHz)
11.3k
44.2k
R22
20k
100
1562 TA15b
1562fa
1000