Linear DC266B-A Quick setup guide

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DEMO MANUAL DC266B
Description
LTC1562/LTC1562-2
Quad 2nd Order Active RC Filter IC
Demonstration circuit DC266B-A is for the evaluation of
8th order filter circuits using an LTC1562 (no dash) and
DC266B-B for an LTC1562-2. LTC1562 and LTC1562-2
are quad 2nd order active-RC filter building blocks. The
LTC1562 or LTC1562-2 2nd order sections can be con-
figured with external resistors to implement lowpass and
narrow or wide band bandpass filters. The frequency
range for a lowpass filter is 10kHz to 150kHz and 20kHz to
300kHz for the LTC1562 and LTC1562-2 respectively. The
frequency range for a bandpass filter is 20kHz to 120kHz
and 40kHz to 250kHz for the LTC1562 and LTC1562-2
respectively (the LTC1562A is higher precision version
of the LTC1562).
For testing and evaluation, the DC266B-A is configured as
an 8th order, 50kHz bandpass filter and the DC266B-B is
configured as an 8th order, 200kHz bandpass filter.
L, LT, LTC, LTM, Linear Technology, LTspce, FilterCAD and the Linear logo are registered
trademarks of Linear Technology Corporation. All other trademarks are the property of their
respective owners.
Ltc1562 anD Ltc1562-2 BLock Diagram
For other possible LTC1562 or LTC1562-2 configurations,
the DC226B-A and DC226B-B have unused pads for 0805
surface mount resistors and capacitors preconfigured
with PCB traces to allow for the following filter circuits:
1. 8th order lowpass filter
2. Dual 4th or 5th order lowpass filter
3. 8th order narrow band bandpass
4. 8th order wide band bandpass.
Refer to the LTC1562 or LTC1562-2 data sheet for com-
prehensive filter design information.
Design files for this circuit board are available at
http://www.linear.com/demo/DC266B
DC266 BD
2ND ORDER SECTIONS
R
R
INV V1 V2
C
SHUTDOWN
SWITCH
SHUTDOWN
SWITCH AGND
V+
V–
–
+
INV V1 V2
INV V1 V2 INV V1 V2
C
C C
A B
D C
–
+
–
+
–
+
∫ ∫
INV V1 V2
C
–
+
INV V1 V2
C
A B
–
+
∫ ∫
∫ ∫
*100kHz FOR
LTC1562 AND
200kHz FOR
LTC1562-2
2ND ORDER LOWPASS (V2) AND BANDPASS (V1) 2ND ORDER BANDPASS (V2) AND HIGHPASS (V1)
THE MAXIMUM
FREQUENCY ERROR IS
±0.6% FOR LTC162A,
±1.0% FOR LTC1562 AND
±1.7% FOR LTC1562-2
*
RQ
CIN
VIN
R2
*
RQ RIN
VIN
R2
SHDN
V+
V–
6
5
10 9 8 1 2 3
11 12 13 20 19 18
16
PINS 4, 7, 14
AND 17 MUST BE
CONNECTED TO
V–, PIN 16
4
7
14
17
15

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DEMO MANUAL DC266B
Quick start proceDure
See Figure 1 for proper measurement equipment setup
and follow the procedure below.
1. Set SW1 to DUAL.
2. With power off, connect a dual 5V power supply to +V
and –V.
3. Connect a function generator to IN.
4. For a DC266B-A, set the function generator to a 2VP-P,
50kHz, sine wave.
5. For a DC266B-B, set the function generator to a 2VP-P,
200kHz, sine wave.
6. Connect an oscilloscope channel to OUT.
7. For a DC266B-A, set the scaling of an oscilloscope to
1V/20µs per division.
For a DC266B-B, set the scaling of an oscilloscope to
1V/5µs per division.
8. Power up the system and the oscilloscope should show
2VP-P sine wave.
9. To test stopband attenuation of DC266B-A, set the
input frequency to 25kHz or 75kHz.
10.To test stopband attenuation of DC266B-B, set the
input frequency to 150kHz or 250kHz.
Figure 1. Quick Start Test Equipment Setup

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DEMO MANUAL DC266B
Dc266B FiLter circuits
For testing and evaluation, the DC266B-A is configured
as an 8th order, 50kHz bandpass filter (Figure 2) and the
DC266B-B is configured as an 8th order, 200kHz bandpass
filter (Figure 3). The external resistors for the 50kHz and
200kHz bandpass filter are ±0.1% precision to highlight
the frequency accuracy of the LTC1562A or LTC1562-2
(±0.6% and ±1.7% 2nd order frequency error for the
LTC1562A and LTC1562-2 respectively).
NOTE 1:The precision of external resistors and capaci-
tors depend on the filter type. A lowpass and wideband
bandpass filter can be implemented with ±1% resistors
and±5% capacitors.A narrowbandbandpassfilterrequires
±0.1% resistors and 1% capacitors to implement a 100%
reliable manufacturing lot.
NOTE 2:In a dual supply operation, the DC266B connects
twoSchottkydiodesinserieswith the V–supply. The diodes
provide 100% protection for possible 2nd order oscilla-
tions when a V1 or V2 output approaches the supply rails.
The V1 diodes can be shorted out on the board if testing
the filter circuit with an input that saturates the output
nodes does not produce any oscillations.
Re-Configuring the DC266B
Removing the default passive components (RIN1, RQ1,
R21, Z1B, RQ2, R22, Z1C, RQ3, R23, Z1A, RQ4, R24) a
variety of bandpass and lowpass LTC1562/LTC1562-2
filter circuits can be implemented.
The LTC1562 and LTC1562-2 data sheets provide filter
design guides and a variety of pre-designed filter circuits.
The typical fCand gain error can be evaluated by LTspice
®
.*
A guideline is to consider an fCerror greater than 3% or
a passband gain peak greater than 2dB as an indication
the circuit is operating beyond a reliable fCfrequency (an
fCerror less than 3% or gain error less than 2dB can be
adjusted using the external resistors).
*LTspice is a high performance simulator, schematic capture and waveform viewer available for
free download at www.linear.com/LTspice.
Figure 2. The Default DC266B-A Circuit
INV
V1
V2
V+
V2
V1
INV
INV
V1
V2
AGND
V–
V2
V1
INV
U1
LTC1562A
V+
BPIN
V+
BPOUT
V–
V–
V1
AC1
V2
5
R21 46.4k
RQ2 68.1k
R22 39.2k
RQ1 61.9k
R23
53.6k
RQ3 88.7k
R24 33.2k
RQ4 100k
0.1µF
Z1C
61.9k
Z1A
61.9k
RIN1
150k
Z1B
61.9k
V3
–5
0.1µF
LTC1562A LINEAR PHASE 8TH ORDER BPF
(SHORT TRANSIENT RESPONSE)
fCENTER = 50kHz
–3dB BW = 10kHz
LTC1562A, ±0.6% 2ND ORDER FREQUENCY ERROR
DUAL SUPPLY CIRCUIT
.ac oct 250 5k 200k
+
–
+
–
+
–
DC266 F02a
GAIN =150k
RIN1
•61.9k
Z1B
RIN1=150k
GAIN
Z1B =61.9k
GAIN
MAXIMUM GAIN: 40dB
FREQUENCY
5kHz
50kHz
200kHz
–100
–90
–80
–70
–60
–50
–40
–30
–20
–10
0
10
MAGNITUTE (dB)
Magnitude vs Frequency
DC266 F02b

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DEMO MANUAL DC266B
Dc266B FiLter circuits
Figure 3. The Default DC266B-B Circuit
Figure 4. Reconfigured for LTC1562A 8th Order, 50kHz High Selectivity, Bandpass Filter
INV
V1
V2
V+
V2
V1
INV
INV
V1
V2
AGND
V–
V2
V1
INV
U1
LTC1562-2
V+
BPIN
V+
BPOUT
V–
V–
V1
AC1
V2
5
R21 9.09k
RQ2 23.2k
R22 7.32k
RQ1 23.2k
R23
10.5k
RQ3 29.4k
R24 6.34k
RQ4 29.4k
0.1µF
Z1C
23.2k
Z1A
23.2k
RIN1
23.2k
Z1B
23.2k
V3
–5
0.1µF
LTC1562-2 LINEAR PHASE 8TH ORDER BPF
(SHORT TRANSIENT RESPONSE)
fCENTER = 200kHz
–3dB BW = 40kHz
LTC1562-2, ±1.7% 2ND ORDER FREQUENCY ERROR
DUAL SUPPLY CIRCUIT
.ac oct 250 20k 800k
+
–
+
–
+
–
DC266 F03a
GAIN =23.2k
RIN1
•23.2k
Z1B
RIN1=23.2k
GAIN
Z1B =23.2k
GAIN
MAXIMUM GAIN: 20dB
INV
V1
V2
V+
V2
V1
INV
INV
V1
V2
AGND
V–
V2
V1
INV
U1
LTC1562A
+
–
+
–
CIN1
(CIN)
Z2B
(CIN)
RQ2 205k
ALL RESISTORS: 0.1%
Z1C AND Z1A CAPACITORS: 1%
CIN1 AND Z2B: 5%
V+
BPIN
V+
BPOUT
V1
AC1
V2
5
R21 41.2k
R22 41.2
RQ1 205k
R23
42.2k
RQ3 232k
R24 39.2k
RQ4 232k
0.1µF
Z1A 39pF
Z2C
232k
Z2A 301k
Z1C 18pF
0.1µF
LTC1562A HIGH SELECTIVITY 8TH ORDER BPF
fCENTER = 50kHz
–3dB = 2kHz
LTC1562A 2ND ORDER SECTION FREQUENCY ERROR: ±0.6%
SINGLE SUPPLY CIRCUIT
DC266 F04a
GAIN CIN
0dB 6.8pF
10dB 10pF
21dB 22pF
31dB 39pF
40dB 68pF
MAXIMUM GAIN, 40dB
.ac lin 500 10k 100k
.param CIN = 6.8p
FREQUENCY
20kHz
200kHz
800kHz
–100
–90
–80
–70
–60
–50
–40
–30
–20
–10
0
10
MAGNITUTE (dB)
Magnitude vs Frequency
DC266 F03b
FREQUENCY (Hz)
5kHz
50kHz
200kHz
–100
–90
–80
–70
–60
–50
–40
–30
–20
–10
0
10
MAGNITUTE (dB)
Magnitude vs Frequency
DC266 F04b

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DEMO MANUAL DC266B
Information furnished by Linear Technology Corporation is believed to be accurate and reliable.
However, no responsibility is assumed for its use. Linear Technology Corporation makes no representa-
tion that the interconnection of its circuits as described herein will not infringe on existing patent rights.
Dc266B FiLter circuits
Figure 5. Reconfigured for LTC1562A 8th Order, 100kHz High Selectivity, Bandpass Filter
INV
V1
V2
V+
V2
V1
INV
INV
V1
V2
AGND
V–
V2
V1
INV
U1
LTC1562A
+
–
+
–
RIN1
(RGAIN)
Z1B
(RGAIN)
RQ2 100k
RESISTORS: 0.1%
(RIN1 AND Z1B: 1%)
Z1C AND Z1A CAPACITORS: 1%
V+
BPIN
V+
BPOUT
V1
AC1
2.5
V2
5
R21 10.2k
R22 10.2
RQ1 100k
R23
10.5k
RQ3 115k
R24 9.76k
RQ4 115k
0.1µF
Z1A 33pF
Z2C
59k
Z2A 80.6k
Z1C 18pF
0.1µF
LTC1562A HIGH SELECTIVITY 8TH ORDER BPF
fCENTER = 100kHz
–3dB = 4kHz
LTC1562A 2ND ORDER SECTION FREQUENCY ERROR: ±0.6%
SINGLE SUPPLY CIRCUIT
DC266 F05a
.ac lin 500 20k 200k
.param RGAIN = 140k
GAIN =140k
RGAIN
⎛
⎝
⎜⎞
⎠
⎟
2
RGAIN =140k
GAIN
MAXIMUM GAIN: 26dB
FREQUENCY (Hz)
10kHz
100kHz
400kHz
–100
–90
–80
–70
–60
–50
–40
–30
–20
–10
0
10
MAGNITUTE (dB)
Magnitude vs Frequency
DC266 F05b

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DEMO MANUAL DC266B
Linear Technology Corporation
1630 McCarthy Blvd., Milpitas, CA 95035-7417
[phone] ●FAX: [phone] ●www.linear.com
© LINEAR TECHNOLOGY CORPORATION 2016
LT 1116 • PRINTED IN USA
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