Download LTC1563-2/LTC1563-3 - Active RC, 4th Order Lowpass Filter Family

LTC1563-2/LTC1563-3
Active RC, 4th Order
Lowpass Filter Family
U
FEATURES
DESCRIPTIO
■
The LTC®1563-2/LTC1563-3 are a family of extremely
easy-to-use, active RC lowpass filters with rail-to-rail
inputs and outputs and low DC offset suitable for systems
with a resolution of up to 16 bits. The LTC1563-2, with a
single resistor value, gives a unity-gain Butterworth
response. The LTC1563-3, with a single resistor value,
gives a unity-gain Bessel response. The proprietary
architecture of these parts allows for a simple resistor
calculation:
■
■
■
■
■
■
■
■
■
■
■
Extremely Easy to Use—A Single Resistor Value
Sets the Cutoff Frequency (256Hz < fC < 256kHz)
Extremely Flexible—Different Resistor Values
Allow Arbitrary Transfer Functions with or without
Gain (256Hz < fC < 256kHz)
Supports Cutoff Frequencies Up to 360kHz Using
FilterCADTM
LTC1563-2: Unity-Gain Butterworth Response Uses a
Single Resistor Value, Different Resistor Values
Allow Other Responses with or without Gain
LTC1563-3: Unity-Gain Bessel Response Uses a
Single Resistor Value, Different Resistor Values
Allow Other Responses with or without Gain
Rail-to-Rail Input and Output Voltages
Operates from a Single 3V (2.7V Min) to ±5V Supply
Low Noise: 36µVRMS for fC = 25.6kHz, 60µVRMS for
fC = 256kHz
fC Accuracy < ±2% (Typ)
DC Offset < 1mV
Cascadable to Form 8th Order Lowpass Filters
Available in Narrow SSOP-16 Package
U
APPLICATIO S
■
■
■
■
Discrete RC Active Filter Replacement
Antialiasing Filters
Smoothing or Reconstruction Filters
Linear Phase Filtering for Data Communication
Phase Locked Loops
where fC is the desired cutoff frequency. For many applications, this formula is all that is needed to design a filter.
By simply utilizing different valued resistors, gain and
other responses are achieved.
The LTC1563-X features a low power mode, for the lower
frequency applications, where the supply current is reduced by an order of magnitude and a near zero power
shutdown mode.
The LTC1563-Xs are available in the narrow SSOP-16
package (Same footprint as an SO-8 package).
, LTC and LT are registered trademarks of Linear Technology Corporation.
FilterCAD is trademark of Linear Technology Corporation.
All other trademarks are the property of their respective owners.
U
■
R = 10k (256kHz/fC); fC = Cutoff Frequency
TYPICAL APPLICATIO
Frequency Response
Single 3.3V, 256Hz to 256kHz Butterworth Lowpass Filter
0
3.3V
0.1µF
LTC1563-2
3
R
4
5
R
VIN
0.1µF
6
7
8
LP
SA
NC
INVA
NC
LPA
AGND
V
–
16
V+
15
LPB
14
NC
13
INVB
12
NC
11
SB
10
NC
9
EN
( )
10k
fC = 256kHz
R
R
–10
VOUT
R = 10k
fC = 256kHz
–20
GAIN (dB)
1
2
R
10
R
–30
R = 10M
fC = 256Hz
–40
–50
–60
R
–70
–80
100
1563 TA01
1k
10k
100k
FREQUENCY (Hz)
www.BDTIC.com/Linear
1M
1563 TA02
156323fa
1
LTC1563-2/LTC1563-3
W
U
U
W W
W
(Note 1)
U
ABSOLUTE MAXIMUM RATINGS
PACKAGE/ORDER INFORMATION
TOP VIEW
Total Supply Voltage (V + to V –) ............................... 11V
Maximum Input Voltage at
Any Pin ....................... (V – – 0.3V) ≤ VPIN ≤ (V + + 0.3V)
Power Dissipation .............................................. 500mW
Operating Temperature Range
LTC1563C ............................................... 0°C to 70°C
LTC1563I ............................................ – 40°C to 85°C
Storage Temperature Range ................. – 65°C to 150°C
Lead Temperature (Soldering, 10 sec).................. 300°C
LP 1
16 V +
SA 2
15 LPB
NC 3
14 NC
INVA 4
ORDER PART
NUMBER
LTC1563-2CGN
LTC1563-3CGN
LTC1563-2IGN
LTC1563-3IGN
13 INVB
NC 5
12 NC
LPA 6
11 SB
AGND 7
10 NC
V– 8
9
GN PART
MARKING
EN
GN PACKAGE
16-LEAD PLASTIC SSOP
15632
15633
15632I
15633I
TJMAX = 150°C, θJA = 135°C/ W
NOTE: PINS LABELED NC ARE NOT CONNECTED
INTERNALLY AND SHOULD BE CONNECTED TO THE
SYSTEM GROUND
Order Options Tape and Reel: Add #TR
Lead Free: Add #PBF Lead Free Tape and Reel: Add #TRPBF
Lead Free Part Marking: http://www.linear.com/leadfree/
Consult LTC Marketing for Military grade parts.
ELECTRICAL CHARACTERISTICS
The ● denotes specifications which apply over the full operating temperature range, otherwise specifications are TA = 25°C.
VS = Single 4.75V, EN pin to logic “low,” Gain = 1, RFIL = R11 = R21 = R31 = R12 = R22 = R32, specifications apply to both the high
speed (HS) and low power (LP) modes unless otherwise noted.
PARAMETER
CONDITIONS
Specifications for Both LTC1563-2 and LTC1563-3
MIN
TYP
MAX
UNITS
Total Supply Voltage (VS), HS Mode
●
3
11
V
Total Supply Voltage (VS), LP Mode
●
2.7
11
V
2.9
4.55
4.8
Output Voltage Swing High (LPB Pin)
HS Mode
VS = 3V, fC = 25.6kHz, RFIL = 100k, RL = 10k to GND
VS = 4.75V, fC = 25.6kHz, RFIL = 100k, RL = 10k to GND
VS = ±5V, fC = 25.6kHz, RFIL = 100k, RL = 10k to GND
●
●
●
Output Voltage Swing Low (LPB Pin)
HS Mode
VS = 3V, fC = 25.6kHz, RFIL = 100k, RL = 10k to GND
VS = 4.75V, fC = 25.6kHz, RFIL = 100k, RL = 10k to GND
VS = ±5V, fC = 25.6kHz, RFIL = 100k, RL = 10k to GND
●
●
●
Output Swing High (LPB Pin)
LP Mode
VS = 2.7V, fC = 25.6kHz, RFIL = 100k, RL = 10k to GND
VS = 4.75V, fC = 25.6kHz, RFIL = 100k, RL = 10k to GND
VS = ±5V, fC = 25.6kHz, RFIL = 100k, RL = 10k to GND
●
●
●
Output Swing Low (LPB Pin)
LP Mode
VS = 2.7V, fC = 25.6kHz, RFIL = 100k, RL = 10k to GND
VS = 4.75V, fC = 25.6kHz, RFIL = 100k, RL = 10k to GND
VS = ±5V, fC = 25.6kHz, RFIL = 100k, RL = 10k to GND
●
●
●
0.01
0.015
– 4.95
0.05
0.05
– 4.9
DC Offset Voltage, HS Mode
(Section A Only)
VS = 3V, fC = 25.6kHz, RFIL = 100k
VS = 4.75V, fC = 25.6kHz, RFIL = 100k
VS = ±5V, fC = 25.6kHz, RFIL = 100k
●
●
●
±1.5
±1.0
±1.5
±3
±3
±3
mV
mV
mV
DC Offset Voltage, LP Mode
(Section A Only)
VS = 2.7V, fC = 25.6kHz, RFIL = 100k
VS = 4.75V, fC = 25.6kHz, RFIL = 100k
VS = ±5V, fC = 25.6kHz, RFIL = 100k
●
●
●
±2
±2
±2
±6
±6
±7
mV
mV
mV
DC Offset Voltage, HS Mode
(Input to Output, Sections A, B Cascaded)
VS = 3V, fC = 25.6kHz, RFIL = 100k
VS = 4.75V, fC = 25.6kHz, RFIL = 100k
VS = ±5V, fC = 25.6kHz, RFIL = 100k
●
●
●
±1.5
±1.0
±1.5
±3
±3
±3
mV
mV
mV
2
2.95
4.7
4.9
0.015
0.02
– 4.95
2.6
4.55
4.8
www.BDTIC.com/Linear
V
V
V
0.05
0.05
– 4.9
2.65
4.65
4.9
V
V
V
V
V
V
V
V
V
156323fa
LTC1563-2/LTC1563-3
ELECTRICAL CHARACTERISTICS
The ● denotes specifications which apply over the full operating temperature range, otherwise specifications are TA = 25°C.
VS = Single 4.75V, EN pin to logic “low,” Gain = 1, RFIL = R11 = R21 = R31 = R12 = R22 = R32, specifications apply to both the high
speed (HS) and low power (LP) modes unless otherwise noted.
PARAMETER
DC Offset Voltage, LP Mode
(Input to Output, Sections A, B Cascaded)
CONDITIONS
VS = 2.7V, fC = 25.6kHz, RFIL = 100k
VS = 4.75V, fC = 25.6kHz, RFIL = 100k
VS = ±5V, fC = 25.6kHz, RFIL = 100k
●
●
●
MIN
TYP
±2
±2
±2
MAX
±7
±7
±8
UNITS
mV
mV
mV
DC Offset Voltage Drift, HS Mode
(Input to Output, Sections A, B Cascaded)
VS = 3V, fC = 25.6kHz, RFIL = 100k
VS = 4.75V, fC = 25.6kHz, RFIL = 100k
VS = ±5V, fC = 25.6kHz, RFIL = 100k
●
●
●
10
10
10
µV/°C
µV/°C
µV/°C
DC Offset Voltage Drift, LP Mode
(Input to Output, Sections A, B Cascaded)
VS = 2.7V, fC = 25.6kHz, RFIL = 100k
VS = 4.75V, fC = 25.6kHz, RFIL = 100k
VS = ±5V, fC = 25.6kHz, RFIL = 100k
●
●
●
10
10
10
µV/°C
µV/°C
µV/°C
AGND Voltage
VS = 4.75V, fC = 25.6kHz, RFIL = 100k
●
2.375
2.40
Power Supply Current, HS Mode
VS = 3V, fC = 25.6kHz, RFIL = 100k
VS = 4.75V, fC = 25.6kHz, RFIL = 100k
VS = ±5V, fC = 25.6kHz, RFIL = 100k
●
●
●
8.0
10.5
15
14
17
23
mA
mA
mA
Power Supply Current, LP Mode
VS = 2.7V, fC = 25.6kHz, RFIL = 100k
VS = 4.75V, fC = 25.6kHz, RFIL = 100k
VS = ±5V, fC = 25.6kHz, RFIL = 100k
●
●
●
1.0
1.4
2.3
1.8
2.5
3.5
mA
mA
mA
Shutdown Mode Supply Current
VS = 4.75V, fC = 25.6kHz, RFIL = 100k
●
1
20
µA
EN Input
Logic Low Level
VS = 3V
VS = 4.75V
VS = ±5V
●
●
●
0.8
1
1
V
V
V
EN Input
Logic High Level
VS = 3V
VS = 4.75V
VS = ±5V
●
●
●
LP
Logic Low Level
VS = 3V
VS = 4.75V
VS = ±5V
●
●
●
LP
Logic High Level
VS = 3V
VS = 4.75V
VS = ±5V
●
●
●
2.5
4.3
4.4
Cutoff Frequency Range, fC
HS Mode
(Note 2)
VS = 3V
VS = 4.75V
VS = ±5V
●
●
●
0.256
0.256
0.256
256
256
256
kHz
kHz
kHz
Cutoff Frequency Range, fC
LP Mode
(Note 2)
VS = 2.7V
VS = 4.75V
VS = ±5V
●
●
●
0.256
0.256
0.256
25.6
25.6
25.6
kHz
kHz
kHz
Cutoff Frequency Accuracy, HS Mode
fC = 25.6kHz
VS = 3V, RFIL = 100k
VS = 4.75V, RFIL = 100k
VS = ±5V, RFIL = 100k
●
●
●
–2.0
–2.0
–2.0
±1.5
±1.5
±1.5
3.5
3.5
3.5
%
%
%
Cutoff Frequency Accuracy, HS Mode
fC = 256kHz
VS = 3V, RFIL = 10k
VS = 4.75V, RFIL = 10k
VS = ±5V, RFIL = 10k
●
●
●
–5
–5
–5
±1.5
±1.5
±1.5
2.5
2.5
2.5
%
%
%
Cutoff Frequency Accuracy, LP Mode
fC = 25.6kHz
VS = 2.7V, RFIL = 100k
VS = 4.75V, RFIL = 100k
VS = ±5V, RFIL = 100k
●
●
●
–3
–3
–3
±1.5
±1.5
±1.5
3
3
3
%
%
%
Cutoff Frequency Temperature Coefficient
(Note 3)
●
2.35
2.5
4.3
4.4
V
V
V
V
0.8
1
1
V
V
V
V
V
V
LTC1563-2 Transfer Function Characteristics
www.BDTIC.com/Linear
±1
ppm/°C
156323fa
3
LTC1563-2/LTC1563-3
ELECTRICAL CHARACTERISTICS
The ● denotes specifications which apply over the full operating temperature range, otherwise specifications are TA = 25°C.
VS = Single 4.75V, EN pin to logic “low,” Gain = 1, RFIL = R11 = R21 = R31 = R12 = R22 = R32, specifications apply to both the high
speed (HS) and low power (LP) modes unless otherwise noted.
PARAMETER
Passband Gain, HS Mode, fC = 25.6kHz
VS = 4.75V, RFIL = 100k
CONDITIONS
Test Frequency = 2.56kHz (0.1 • fC)
Test Frequency = 12.8kHz (0.5 • fC)
●
●
Stopband Gain, HS Mode, fC = 25.6kHz
VS = 4.75V, RFIL = 100k
Test Frequency = 51.2kHz (2 • fC)
Test Frequency = 102.4kHz (4 • fC)
●
●
Passband Gain, HS Mode, fC = 256kHz
VS = 4.75V, RFIL = 10k
Test Frequency = 25.6kHz (0.1 • fC)
Test Frequency = 128kHz (0.5 • fC)
●
●
Stopband Gain, HS Mode, fC = 256kHz
VS = 4.75V, RFIL = 10k
Test Frequency = 400kHz (1.56 • fC)
Test Frequency = 500kHz (1.95 • fC)
●
●
Passband Gain, LP Mode, fC = 25.6kHz
VS = 4.75V, RFIL = 100k
Test Frequency = 2.56kHz (0.1 • fC)
Test Frequency = 12.8kHz (0.5 • fC)
●
●
Stopband Gain, LP Mode, fC = 25.6kHz
VS = 4.75V, RFIL = 100k
Test Frequency = 51.2kHz (2 • fC)
Test Frequency = 102.4kHz (4 • fC)
●
●
Cutoff Frequency Range, fC
HS Mode
(Note 2)
VS = 3V
VS = 4.75V
VS = ±5V
●
●
●
Cutoff Frequency Range, fC
LP Mode
(Note 2)
VS = 2.7V
VS = 4.75V
VS = ±5V
Cutoff Frequency Accuracy, HS Mode
fC = 25.6kHz
MIN
– 0.2
– 0.3
TYP
0
0
MAX
0.2
0.3
UNITS
dB
dB
– 24
– 48
– 21.5
– 46
dB
dB
0
0
0.2
0.5
dB
dB
– 15.7
– 23.3
–13.5
– 21.5
dB
dB
0
– 0.02
0.25
0.6
dB
dB
– 24
– 48
– 22
– 46.5
dB
dB
0.256
0.256
0.256
256
256
256
kHz
kHz
kHz
●
●
●
0.256
0.256
0.256
25.6
25.6
25.6
kHz
kHz
kHz
VS = 3V, RFIL = 100k
VS = 4.75V, RFIL = 100k
VS = ±5V, RFIL = 100k
●
●
●
–3
–3
–3
±2
±2
±2
5.5
5.5
5.5
%
%
%
Cutoff Frequency Accuracy, HS Mode
fC = 256kHz
VS = 3V, RFIL = 10k
VS = 4.75V, RFIL = 10k
VS = ±5V, RFIL = 10k
●
●
●
–3
–3
–3
±2
±2
±2
6
6
6
%
%
%
Cutoff Frequency Accuracy, LP Mode
fC = 25.6kHz
VS = 2.7V, RFIL = 100k
VS = 4.75V, RFIL = 100k
VS = ±5V, RFIL = 100k
●
●
●
–4
–4
–4
±3
±3
±3
7
7
7
%
%
%
Cutoff Frequency Temperature Coefficient
(Note 3)
●
Passband Gain, HS Mode, fC = 25.6kHz
VS = 4.75V, RFIL = 100k
Test Frequency = 2.56kHz (0.1 • fC)
Test Frequency = 12.8kHz (0.5 • fC)
●
●
– 0.2
–1.0
– 0.03
– 0.72
0.2
– 0.25
dB
dB
Stopband Gain, HS Mode, fC = 25.6kHz
VS = 4.75V, RFIL = 100k
Test Frequency = 51.2kHz (2 • fC)
Test Frequency = 102.4kHz (4 • fC)
●
●
–13.6
– 34.7
–10
– 31
dB
dB
Passband Gain, HS Mode, fC = 256kHz
VS = 4.75V, RFIL = 10k
Test Frequency = 25.6kHz (0.1 • fC)
Test Frequency = 128kHz (0.5 • fC)
●
●
– 0.03
– 0.72
0.2
– 0.5
dB
dB
Stopband Gain, HS Mode, fC = 256kHz
VS = 4.75V, RFIL = 10k
Test Frequency = 400kHz (1.56 • fC)
Test Frequency = 500kHz (1.95 • fC)
●
●
– 8.3
– 13
–6
–10.5
dB
dB
Passband Gain, LP Mode, fC = 25.6kHz
VS = 4.75V, RFIL = 100k
Test Frequency = 2.56kHz (0.1 • fC)
Test Frequency = 12.8kHz (0.5 • fC)
●
●
– 0.03
– 0.72
0.2
– 0.25
dB
dB
Stopband Gain, LP Mode, fC = 25.6kHz
VS = 4.75V, RFIL = 100k
Test Frequency = 51.2kHz (2 • fC)
Test Frequency = 102.4kHz (4 • fC)
●
●
– 13.6
– 34.7
–11
– 32
dB
dB
– 0.2
– 0.5
– 0.25
– 0.6
LTC1563-3 Transfer Function Characteristics
Note 1: Absolute Maximum Ratings are those value beyond which the life
of a device may be impaired.
Note 2: The minimum cutoff frequency of the LTC1563 is arbitrarily listed
as 256Hz. The limit is arrived at by setting the maximum resistor value
limit at 10MΩ. The LTC1563 can be used with even larger valued resistors.
When using very large values of resistance careful layout and thorough
4
±1
– 0.2
–1.1
– 0.2
–1.0
ppm/°C
assembly practices are required. There may also be greater DC offset at
high temperatures when using such large valued resistors.
Note 3: The cutoff frequency temperature drift at low frequencies is as
listed. At higher cutoff frequencies (approaching 25.6kHz in low power
mode and approaching 256kHz in high speed mode) the internal
amplifier’s bandwidth can effect the cutoff frequency. At these limits the
cutoff frequency temperature drift is ±15ppm/°C.
156323fa
www.BDTIC.com/Linear
LTC1563-2/LTC1563-3
U W
TYPICAL PERFOR A CE CHARACTERISTICS
3.4
5.5
5.5
VS = SINGLE 3.3V
3.0
2.8
HS MODE
2.6
LP MODE
2.4
5.0
OUTPUT VOLTAGE (V)
5.0
OUTPUT VOLTAGE (V)
4.5
HS MODE
4.0
LP MODE
3.5
4.5
HS MODE
4.0
LP MODE
3.5
2.2
3.0
3.0
2.0
100
1k
10k
100k
LOAD RESISTANCE—LOAD TO GROUND (Ω)
2.5
100
1k
10k
100k
LOAD RESISTANCE—LOAD TO GROUND (Ω)
2.5
100
1k
10k
100k
LOAD RESISTANCE—LOAD TO GROUND (Ω)
1563 G01
1563 G02
1563 G03
Output Voltage Swing Low vs
Load Resistance
Output Voltage Swing Low vs
Load Resistance
Output Voltage Swing Low vs
Load Resistance
0.025
0.025
–4.3
VS = SINGLE 3.3V
VS = SINGLE 5V
HS MODE
0.015
LP MODE
–4.4
0.020
OUTPUT VOLTAGE (V)
0.020
VS = ± 5V
HS MODE
0.010
0.005
OUTPUT VOLTAGE (V)
OUTPUT VOLTAGE (V)
VS = ±5V
VS = SINGLE 5V
3.2
OUTPUT VOLTAGE (V)
Output Voltage Swing High vs
Load Resistance
Output Voltage Swing High vs
Load Resistance
Output Voltage Swing High vs
Load Resistance
LP MODE
0.015
0.010
–4.5
–4.6
–4.7
HS MODE
–4.8
0.005
–4.9
0
1k
10k
100k
100
LOAD RESISTANCE—LOAD TO GROUND (Ω)
1563 G04
1563 G05
–40
THD + Noise vs Input Voltage
–40
–40
3.3V SUPPLY
3.3V SUPPLY
3.3V SUPPLY
5V SUPPLY
–60
±5V SUPPLY
–70
–80
fC = 25.6kHz
LOW POWER MODE
fIN = 5kHz
–90
0.1
1
INPUT VOLTAGE (VP-P)
–50
5V SUPPLY
–60
±5V SUPPLY
–70
–80
fC = 25.6kHz
HIGH SPEED MODE
fIN = 5kHz
–90
10
1563 G07
(THD + NOISE)/SIGNAL (dB)
–50
(THD + NOISE)/SIGNAL (dB)
–50
(THD + NOISE)/SIGNAL (dB)
1563 G06
THD + Noise vs Input Voltage
THD + Noise vs Input Voltage
–100
LP MODE
–5.0
100
1k
10k
100k
LOAD RESISTANCE—LOAD TO GROUND (Ω)
0
1k
10k
100k
100
LOAD RESISTANCE—LOAD TO GROUND (Ω)
–100
0.1
1
INPUT VOLTAGE (VP-P)
5V SUPPLY
–60
±5V SUPPLY
–70
–80
fC = 256kHz
HIGH SPEED MODE
fIN = 50kHz
–90
10
–100
0.1
1563 G08
www.BDTIC.com/Linear
1
INPUT VOLTAGE (VP-P)
10
1563 G09
156323fa
5
LTC1563-2/LTC1563-3
U W
TYPICAL PERFOR A CE CHARACTERISTICS
THD + Noise vs Input Frequency
THD + Noise vs Input Frequency
–40
–60
–70
1VP-P
–80
2VP-P
–90
VS = SINGLE 3.3V
HIGH SPEED MODE
fC = 25.6kHz
–70
(THD + NOISE)/SIGNAL (dB)
VS = SINGLE 3.3V
LOW POWER MODE
fC = 25.6kHz
(THD + NOISE)/SIGNAL (dB)
(THD + NOISE)/SIGNAL (dB)
–60
THD + Noise vs Input Frequency
1VP-P
–80
2VP-P
–90
VS = SINGLE 3V
HIGH SPEED MODE
fC = 256kHz
–50
–60
–70
1VP-P
–80
2VP-P
–90
–100
20
10
INPUT FREQUENCY (kHz)
1
1563 G10
1VP-P
–80
2VP-P
–90
–70
1VP-P
–80
2VP-P
–90
3VP-P
20
–100
1563 G13
20
–100
(THD + NOISE)/SIGNAL (dB)
–80
2VP-P
5VP-P
–90
1
10
INPUT FREQUENCY (kHz)
100 200
1563 G15
THD + Noise vs Input Frequency
–40
–60
1VP-P
2VP-P
–80
THD + Noise vs Input Frequency
THD + Noise vs Input Frequency
VS = ± 5V
LOW POWER MODE
fC = 25.6kHz
1VP-P
–70
1563 G14
–60
–70
–60
3VP-P
10
INPUT FREQUENCY (kHz)
1
VS = SINGLE 5V
HIGH SPEED MODE
fC = 256kHz
–50
–90
3VP-P
10
INPUT FREQUENCY (kHz)
1
100 200
–40
VS = SINGLE 5V
HIGH SPEED MODE
fC = 25.6kHz
(THD + NOISE)/SIGNAL (dB)
(THD + NOISE)/SIGNAL (dB)
(THD + NOISE)/SIGNAL (dB)
–70
10
INPUT FREQUENCY (kHz)
THD + Noise vs Input Frequency
–60
VS = SINGLE 5V
LOW POWER MODE
fC = 25.6kHz
1
1563 G12
THD + Noise vs Input Frequency
–60
(THD + NOISE)/SIGNAL (dB)
–100
1563 G11
THD + Noise vs Input Frequency
–100
20
10
INPUT FREQUENCY (kHz)
1
VS = ± 5V
HIGH SPEED MODE
fC = 25.6kHz
–70
(THD + NOISE)/SIGNAL (dB)
–100
1VP-P
–80
2VP-P
5VP-P
–90
VS = ± 5V
HIGH SPEED MODE
fC = 256kHz
–50
–60
1VP-P
–70
2VP-P
–80
–90
–100
1
10
INPUT FREQUENCY (kHz)
20
1563 G16
6
–100
1
10
INPUT FREQUENCY (kHz)
20
–100
5VP-P
1
1563 G17
www.BDTIC.com/Linear
10
INPUT FREQUENCY (kHz)
100 200
1563 G18
156323fa
LTC1563-2/LTC1563-3
U W
TYPICAL PERFOR A CE CHARACTERISTICS
THD + Noise vs Output Load
–80
LP MODE,
2VP-P SIGNAL
–85
–90
HS MODE,
3VP-P SIGNAL
HS MODE,
2VP-P SIGNAL
–75
2VP-P, 50kHz
2VP-P, 20kHz
–80
–85
3VP-P, 50kHz
–90
–95
–95
–100
–100
0 1 2 3 4 5 6 7 8 9 10
OUTPUT LOAD RESISTANCE—LOAD TO GROUND (kΩ)
60
–70
3VP-P, 20kHz
VS = SINGLE 5V
HIGH SPEED MODE
fC = 256kHz
fIN = 20kHz, 50kHz
–80
LP MODE,
2VP-P SIGNAL
–85
HS MODE,
2VP-P SIGNAL
–90
–95
–100
0 1 2 3 4 5 6 7 8 9 10
OUTPUT LOAD RESISTANCE—LOAD TO GROUND (kΩ)
1
10
fC (Hz)
100
1000
fC = 256kHz
0
–10
2VP-P, 50kHz
–20
–80
2VP-P, 20kHz
–85
5VP-P, 50kHz
–90
VS = ± 5V
HIGH SPEED MODE
fC = 256kHz
fIN = 20kHz, 50kHz
–30
LTC1563-2
LTC1563-3
–40
–50
–60
2VP-P, 20kHz
–70
–80
–100
0 1 2 3 4 5 6 7 8 9 10
OUTPUT LOAD RESISTANCE—LOAD TO GROUND (kΩ)
–90
10k
100k
1M
10M
FREQUENCY (Hz)
100M
1563 G24
1563 G23
Crosstalk Rejection vs Frequency
Crosstalk Rejection vs Frequency
–60
–60
DUAL SECOND ORDER
BUTTERWORTH
fC = 25.6kHz
HS OR LP MODE
DUAL SECOND ORDER
BUTTERWORTH
fC = 256kHz
HIGH SPEED MODE
–70
CROSSTALK (dB)
–70
CROSSTALK (dB)
10
Stopband Gain vs Input Frequency
–75
1563 G22
–80
–90
–100
–110
20
10
–95
HS MODE,
5VP-P SIGNAL
HS MODE
1563 G21
–70
(THD + NOISE)/SIGNAL (dB)
(THD + NOISE)/SIGNAL (dB)
LP MODE,
5VP-P SIGNAL
30
THD + Noise vs Output Load
VS = ± 5V
fC = 25.6kHz
fIN = 5kHz
LP MODE
40
1563 G20
THD + Noise vs Output Load
–75
TA = 25°C
50
0k
0.1
0 1 2 3 4 5 6 7 8 9 10
OUTPUT LOAD RESISTANCE—LOAD TO GROUND (kΩ)
1563 G19
–70
TOTAL INTEGRATED NOISE (µVRMS)
–75
VS = SINGLE 5V
fC = 25.6kHz
fIN = 5kHz
GAIN (dB)
LP MODE,
3VP-P SIGNAL
(THD + NOISE)/SIGNAL (dB)
(THD + NOISE)/SIGNAL (dB)
–70
Output Voltage Noise vs Cutoff
Frequency
THD + Noise vs Output Load
–80
–90
–100
1
10
FREQUENCY (kHz)
100
–110
1k
10k
100k
FREQUENCY (Hz)
1563 G25
www.BDTIC.com/Linear
1M
1563 G26
156323fa
7
LTC1563-2/LTC1563-3
U
U
U
PIN FUNCTIONS
LP (Pin 1): Low Power. The LTC1563-X has two operating
modes: Low Power and High Speed. Most applications will
use the High Speed operating mode. Some lower frequency, lower gain applications can take advantage of the
Low Power mode. When placed in the Low Power mode,
the supply current is nearly an order of magnitude lower
than the High Speed mode. Refer to the Applications
Information section for more information on the Low
Power mode.
LPA, LPB (Pins 6, 15): Lowpass Output. These pins are
the rail-to-rail outputs of an op amp. Each output is
designed to drive a nominal net load of 5kΩ and 20pF.
Refer to the Applications Information section for more
details on output loading effects.
The LTC1563-X is in the High Speed mode when the
LP input is at a logic high level or is open-circuited. A small
pull-up current source at the LP input defaults the
LTC1563-X to the High Speed mode if the pin is left open.
The part is in the Low Power mode when the pin is pulled
to a logic low level or connected to V –.
AGND (Pin 7): Analog Ground. The AGND pin is the
midpoint of an internal resistive voltage divider developing
a potential halfway between the V + and V – pins. The
equivalent series resistance is nominally 10kΩ. This serves
as an internal ground reference. Filter performance will
reflect the quality of the analog signal ground. An analog
ground plane surrounding the package is recommended.
The analog ground plane should be connected to any
digital ground at a single point. Figures 1 and 2 show the
proper connections for dual and single supply operation.
SA, SB (Pins 2, 11): Summing Pins. These pins are a
summing point for signals fed forward and backward.
Capacitance on the SA or SB pin will cause excess peaking
of the frequency response near the cutoff frequency. The
three external resistors for each section should be located
as close as possible to the summing pin to minimize this
effect. Refer to the Applications Information section for
more details.
V –, V + (Pins 8, 16): The V – and V + pins should be
bypassed with 0.1µF capacitors to an adequate analog
ground or ground plane. These capacitors should be
connected as closely as possible to the supply pins. Low
noise linear supplies are recommended. Switching supplies are not recommended as they will decrease the
filter’s dynamic range. Refer to Figures 1 and 2 for the
proper connections for dual and single supply operation.
NC (Pins 3, 5, 10, 12, 14): These pins are not connected
internally. For best performance, they should be connected to ground.
EN (Pin 9): ENABLE. When the EN input goes high or is
open-circuited, the LTC1563-X enters a shutdown state
and only junction leakage currents flow. The AGND pin, the
LPA output and the LPB output assume high impedance
states. If an input signal is applied to a complete filter
circuit while the LTC1563-X is in shutdown, some signal
will normally flow to the output through passive components around the inactive part.
INVA, INVB (Pins 4, 13): Inverting Input. Each of the INV
pins is an inverting input of an op amp. Note that the INV
pins are high impedance, sensitive nodes of the filter and
very susceptible to coupling of unintended signals.
Capacitance on the INV nodes will also affect the frequency response of the filter sections. For these reasons,
printed circuit connections to the INV pins must be kept as
short as possible.
8
A small internal pull-up current source at the EN input
defaults the LTC1563 to the shutdown state if the EN pin
is left floating. Therefore, the user must connect the EN pin
to V – (or a logic low) to enable the part for normal
operation.
www.BDTIC.com/Linear
156323fa
LTC1563-2/LTC1563-3
U
U
U
PIN FUNCTIONS
Dual Supply Power and Ground Connections
Single Supply Power and Ground Connections
LTC1563-X
ANALOG
GROUND
PLANE
1
2
3
4
5
6
7
8
V–
LTC1563-X
16
V+
LP
SA
LPB
NC
NC
INVA
INVB
NC
NC
LPA
SB
AGND
NC
V–
EN
ANALOG
GROUND
PLANE
V+
15
0.1µF
1
2
14
3
13
4
12
5
11
6
10
7
+
9
8
0.1µF
V+
LP
SA
LPB
NC
NC
INVA
INVB
NC
NC
LPA
SB
AGND
NC
V–
EN
16
15
V+
0.1µF
14
13
12
11
10
9
0.1µF
SINGLE POINT
SYSTEM GROUND
SINGLE POINT
SYSTEM GROUND
DIGITAL
GROUND PLANE
(IF ANY)
DIGITAL
GROUND PLANE
(IF ANY)
1563 PF02
1563 PF01
W
BLOCK DIAGRA
R21
R22
VOUT
R11
R31
R12
R32
VIN
+
16 V
C1B
C1A
SHUTDOWN
SWITCH
2 SA
20k
4
INVA
AGND 7
C2A
AGND
20k
SHUTDOWN
SWITCH
8 V–
9
EN
1
LP
–
+
11 SB
6 LPA
13
INVB
C2B
AGND
–
+
15 LPB
AGND
LTC1563-X
1563 BD
PATENT PENDING
www.BDTIC.com/Linear
156323fa
9
LTC1563-2/LTC1563-3
U
W
U
U
APPLICATIONS INFORMATION
Functional Description
The LTC1563-2/LTC1563-3 are a family of easy-to-use,
4th order lowpass filters with rail-to-rail operation. The
LTC1563-2, with a single resistor value, gives a unity-gain
filter approximating a Butterworth response. The
LTC1563-3, with a single resistor value, gives a unity-gain
filter approximating a Bessel (linear phase) response. The
proprietary architecture of these parts allows for a simple
unity-gain resistor calculation:
R = 10k(256kHz/fC)
where fC is the desired cutoff frequency. For many applications, this formula is all that is needed to design a filter.
For example, a 50kHz filter requires a 51.2k resistor. In
practice, a 51.1k resistor would be used as this is the
closest E96, 1% value available.
The LTC1563-X is constructed with two 2nd order sections. The output of the first section (section A) is simply
fed into the second section (section B). Note that section
A and section B are similar, but not identical. The parts are
designed to be simple and easy to use.
By simply utilizing different valued resistors, gain, other
transfer functions and higher cutoff frequencies are
achieved. For these applications, the resistor value calculation gets more difficult. The tables of formulas provided
later in this section make this task much easier. For best
results, design these filters using FilterCAD Version 3.0 (or
newer) or contact the Linear Technology Filter Applications group for assistance.
Cutoff Frequency (fC) and Gain Limitations
The LTC563-X has both a maximum fC limit and a minimum fC limit. The maximum fC limit (256kHz in High Speed
mode and 25.6kHz in the Low Power mode) is set by the
speed of the LTC1563-X’s op amps. At the maximum fC,
the gain is also limited to unity.
A minimum fC is dictated by the practical limitation of
reliably obtaining large valued, precision resistors. As the
desired fC decreases, the resistor value required increases.
When fC is 256Hz, the resistors are 10M. Obtaining a
reliable, precise 10M resistance between two points on a
printed circuit board is somewhat difficult. For example, a
10M resistor with only 200MΩ of stray, layout related
10
resistance in parallel, yields a net effective resistance of
9.52M and an error of – 5%. Note that the gain is also
limited to unity at the minimum fC.
At intermediate fC, the gain is limited by one of the two
reasons discussed above. For best results, design filters
with gain using FilterCAD Version 3 (or newer) or contact
the Linear Technology Filter Applications Group for
assistance.
While the simple formula and the tables in the applications
section deliver good approximations of the transfer functions, a more accurate response is achieved using FilterCAD.
FilterCAD calculates the resistor values using an accurate
and complex algorithm to account for parasitics and op
amp limitations. A design using FilterCAD will always yield
the best possible design. By using the FilterCAD design
tool you can also achieve filters with cutoff frequencies
beyond 256kHz. Cutoff frequencies up to 360kHz are
attainable.
Contact the Linear Technology Filter Applications Group
for a copy the FilterCAD software. FilterCAD can also be
downloaded from our website at www.linear.com.
DC Offset, Noise and Gain Considerations
The LTC1563-X is DC offset trimmed in a 2-step manner.
First, section A is trimmed for minimum DC offset. Next,
section B is trimmed to minimize the total DC offset
(section A plus section B). This method is used to give the
minimum DC offset in unity gain applications and most
higher gain applications.
For gains greater than unity, the gain should be distributed
such that most of the gain is taken in section A, with
section B at a lower gain (preferably unity). This type of
gain distribution results in the lowest noise and lowest DC
offset. For high gain, low frequency applications, all of the
gain is taken in section A, with section B set for unity-gain.
In this configuration, the noise and DC offset is dominated
by those of section A. At higher frequencies, the op amps’
finite bandwidth limits the amount of gain that section A
can reliably achieve. The gain is more evenly distributed in
this case. The noise and DC offset of section A is now
multiplied by the gain of section B. The result is slightly
higher noise and offset.
www.BDTIC.com/Linear
156323fa
LTC1563-2/LTC1563-3
U
W
U
U
APPLICATIONS INFORMATION
Resistive loading affects the maximum output signal swing
and signal distortion. If the output load is excessive, the
output swing is reduced and distortion is increased. All of
the output voltage swing testing on the LTC1563-X is done
with R22 = 100k and a 10k load resistor. For best undistorted
output swing, the output load resistance should be greater
than 10k.
Capacitive loading on the output reduces the stability of
the op amp. If the capacitive loading is sufficiently high,
the stability margin is decreased to the point of oscillation
at the output. Capacitive loading should be kept below
30pF. Good, tight layout techniques should be maintained
at all times. These parts should not drive long traces and
must never drive a long coaxial cable. When probing the
LTC1563-X, always use a 10x probe. Never use a 1x probe.
A standard 10x probe has a capacitance of 10pF to 15pF
while a 1x probe’s capacitance can be as high as 150pF.
The use of a 1x probe will probably cause oscillation.
For larger capacitive loads, a series isolation resistor can
be used between the part and the capacitive load. If the
load is too great, a buffer must be used.
To minimize the effects of parasitic layout capacitance, all
of the resistors for section A should be placed as close as
possible to the SA pin. Place the R31 resistor first so that
it is as close as possible to the SA pin on one end and as
close as possible to the INVA pin on the other end. Use the
same strategy for the layout of section B, keeping all of the
resistors as close as possible to the SB node and first
placing R32 between the SB and INVB pins. It is also best
if the signal routing and resistors are on the same layer as
the part without any vias in the signal path.
Figure 1 illustrates a good layout using the LTC1563-X
with surface mount 0805 size resistors. An even tighter
layout is possible with smaller resistors.
R11
VIN
LTC1563-X
VOUT
R32
R22
The op amps of the LTC1563-X have a rail-to-rail output
stage. To obtain maximum performance, the output loading effects must be considered. Output loading issues can
be divided into resistive effects and capacitive effects.
near the cutoff frequency. Poor layout can give 0.5dB to
1dB of excess peaking.
R21
R31
Output Loading: Resistive and Capacitive
R12
1653 F01
Figure 1. PC Board Layout
Layout Precautions
Single Pole Sections and Odd Order Filters
The LTC1563-X is an active RC filter. The response of the
filter is determined by the on-chip capacitors and the
external resistors. Any external, stray capacitance in parallel with an on-chip capacitor, or to an AC ground, can
alter the transfer function.
The LTC1563 is configured to naturally form even ordered
filters (2nd, 4th, 6th and 8th). With a little bit of work,
single pole sections and odd order filters are easily achieved.
To form a single pole section you simply use the op amp,
the on-chip C1 capacitor and two external resistors as
shown in Figure 2. This gives an inverting section with the
gain set by the R2-R1 ratio and the pole set by the R2-C1
time constant. You can use this pole with a 2nd order
section to form a noninverting gain 3rd order filter or as a
stand alone inverting gain single pole filter.
Capacitance to an AC ground is the most likely problem.
Capacitance on the LPA or LPB pins does not affect the
transfer function but does affect the stability of the op
amps. Capacitance on the INVA and INVB pins will affect
the transfer function somewhat and will also affect the
stability of the op amps. Capacitance on the SA and SB
pins alters the transfer function of the filter. These pins are
the most sensitive to stray capacitance. Stray capacitance
on these pins results in peaking of the frequency response
Figure 3 illustrates another way of making odd order
filters. The R1 input resistor is split into two parts with an
additional capacitor connected to ground in between the
resistors. This “TEE” network forms a single real pole. RB1
www.BDTIC.com/Linear
156323fa
11
LTC1563-2/LTC1563-3
U
U
W
U
APPLICATIONS INFORMATION
should be much larger than RA1 to minimize the interaction of this pole with the 2nd order section. This circuit is
useful in forming dual 3rd order filters and 5th order filters
with a single LTC1563 part. By cascading two parts, 7th
order and 9th order filters are achieved.
R1
RA1
RB1
R2
R3
CP
S
INV
R2
–
VOUT
VIN
C2
(OPEN)
+
S
INV
C1
AGND
LP
1/2 LTC1563
–
C2
RA1 ≈
+
1563 F03
RB1
10
FP =
AGND
2π •
(
1
RA1 • RB1
)
RA1 + RB1
1/2 LTC1563
DC GAIN =
–R2
R1
FP =
CP
Figure 3
LTC1563-2: C1A = 53.9pF, C1B = 39.2pF
LTC1563-3: C1A = 35pF, C1B = 26.8pF
1
2π • R2 • C1
1563 F02
Figure 2
You can also use the TEE network in both sections of the
part to make a 6th order filter. This 6th order filter does not
conform exactly to the textbook responses. Textbook
responses (Butterworth, Bessel, Chebyshev etc.) all have
three complex pole pairs. This filter has two complex pole
pairs and two real poles. The textbook response always
has one section with a low Q value between 0.5 and 0.6. By
replacing this low Q section with two real poles (two real
poles are the same mathematically as a complex pole pair
with a Q of 0.5) and tweaking the Q of the other two
complex pole pair sections you end up with a filter that is
indistinguishable from the textbook filter. The Typical
Applications section illustrates a 100kHz, 6th order pseudoButterworth filter. FilterCAD is a valuable tool for custom
filter design and tweaking textbook responses.
12
LP
C1
What To Do with an Unused Section
If the LTC1563 is used as a 2nd or 3rd order filter, one of
the sections is not used. Do not leave this section unconnected. If the section is left unconnected, the output is left
to float and oscillation may occur. The unused section
should be connected as shown in Figure 4 with the INV pin
connected to the LP pin and the S pin left open.
(OPEN)
S
INV
C1
LP
–
C2
+
AGND
1/2 LTC1563
1563 F04
Figure 4
www.BDTIC.com/Linear
156323fa
LTC1563-2/LTC1563-3
U
U
W
U
APPLICATIONS INFORMATION
4th Order Filter Responses Using the LTC1563-2
10
LTC1563-2
2
3
R31
4
5
R21
6
7
R11
8
16
V+
LP
SA
LPB
NC
NC
INVA
INVB
NC
NC
LPA
SB
AGND
NC
V–
EN
0
VOUT
R22
15
–20
14
R32
13
GAIN (dB)
1
12
11
10
–40
BUTTERWORTH
0.5dB RIPPLE
CHEBYSHEV
0.1dB RIPPLE
CHEBYSHEV
–60
R12
9
–80
NORMALIZED TO fC = 1Hz
–90
1
0.1
FREQUENCY (Hz)
1563 F05
VIN
10
1563 F05a
Figure 5. 4th Order Filter Connections (Power Supply, Ground,
EN and LP Connections Not Shown for Clarity). Table 1 Shows
Resistor Values
Figure 5a. Frequency Response
1.2
1
0
OUTPUT VOLTAGE (V)
1.0
GAIN (dB)
–2
–4
–6
–8
BUTTERWORTH
0.5dB RIPPLE
CHEBYSHEV
0.1dB RIPPLE
CHEBYSHEV
NORMALIZED TO fC = 1Hz
–10
0.1
FREQUENCY (Hz)
0.8
0.6
BUTTERWORTH
0.5dB RIPPLE
CHEBYSHEV
0.1dB RIPPLE
CHEBYSHEV
0.4
0.2
0
1
2
NORMALIZED TO fC = 1Hz
0
0.5
1.0
1.5
2.0
TIME (s)
2.5
1563 F05b
3.0
1563 F05c
Figure 5b. Passband Frequency Response
Figure 5c. Step Response
Table 1. Resistor Values, Normalized to 256kHz Cutoff Frequency (fC), Figure 5. The Passband
Gain, of the 4th Order LTC1563-2 Lowpass Filter, Is Set to Unity. (Note 1)
LP Mode Max fC
HS Mode Max fC
BUTTERWORTH
0.1dB RIPPLE
CHEBYSHEV
0.5dB RIPPLE
CHEBYSHEV
25.6kHz
15kHz
13kHz
256kHz
135kHz
113kHz
R11 = R21 =
10k(256kHz/fC)
13.7k(256kHz/fC)
20.5k(256kHz/fC)
R31 =
10k(256kHz/fC)
10.7k(256kHz/fC)
12.4k(256kHz/fC)
R12 = R22 =
10k(256kHz/fC)
10k(256kHz/fC)
12.1k(256kHz/fC)
R32 =
10k(256kHz/fC)
6.81k(256kHz/fC)
6.98k(256kHz/fC)
Example: In HS mode, 0.1dB ripple Chebyshev, 100kHz cutoff frequency, R11 = R21 = 35k ≅ 34.8k (1%),
R31 = 27.39k ≅ 27.4k (1%), R12 = R22 = 256k ≅ 255k (1%), R32 = 17.43k ≅ 17.4k (1%)
Note 1: The resistor values listed in this table provide good approximations of the listed transfer functions. For the
optimal resistor values, higher gain or other transfer functions, use FilterCAD Version 3.0 (or newer) or contact the
Linear Technology Filter Applications group for assistance.
www.BDTIC.com/Linear
156323fa
13
LTC1563-2/LTC1563-3
U
U
W
U
APPLICATIONS INFORMATION
4th Order Filter Responses Using the LTC1563-3
10
LTC1563-3
2
3
R31
4
5
R21
6
7
R11
8
0
LP
V+
SA
LPB
NC
NC
INVA
INVB
NC
NC
LPA
SB
AGND
NC
V–
EN
16
15
VOUT
R22
–20
14
13
GAIN (dB)
1
R32
12
–40
BESSEL
TRANSITIONAL
GAUSSIAN TO 12dB
TRANSITIONAL
GAUSSIAN TO 6dB
11
–60
10
R12
9
–80
NORMALIZED TO fC = 1Hz
–90
1
0.1
FREQUENCY (Hz)
1563 F06
VIN
1563 F06a
Figure 6. 4th Order Filter Connections (Power Supply, Ground,
EN and LP Connections Not Shown for Clarity). Table 2 Shows
Resistor Values
Figure 6a. Frequency Response
1.2
1.05
BESSEL
TRANSITIONAL
GAUSSIAN TO 12dB
TRANSITIONAL
GAUSSIAN TO 6dB
0.8
0.6
BESSEL
TRANSITIONAL
GAUSSIAN TO 12dB
TRANSITIONAL
GAUSSIAN TO 6dB
0.4
0.2
OUTPUT VOLTAGE (V)
OUTPUT VOLTAGE (V)
1.0
0
10
1.00
NORMALIZED TO fC = 1Hz
0
0.5
1.0
1.5
2.0
TIME (s)
2.5
NORMALIZED TO fC = 1Hz
0.95
3.0
0
0.5
1.0
TIME (s)
1.5
1563 F06b
2.0
1563 F06c
Figure 6b. Step Response
Figure 6c. Step Response—Settling
Table 2. Resistor Values, Normalized to 256kHz Cutoff Frequency (fC), Figure 6. The Passband
Gain, of the 4th Order LTC1563-3 Lowpass Filter, Is Set to Unity. (Note 1)
BESSEL
TRANSITIONAL
GAUSSIAN TO 6dB
TRANSITIONAL
GAUSSIAN TO 12dB
LP Mode Max fC
25.6kHz
20kHz
21kHz
HS Mode Max fC
256kHz
175kHz
185kHz
R11 = R21 =
10k(256kHz/fC)
17.4k(256kHz/fC)
15k(256kHz/fC)
R31 =
10k(256kHz/fC)
13.3k(256kHz/fC)
11.8k(256kHz/fC)
R12 = R22 =
10k(256kHz/fC)
14.3k(256kHz/fC)
10.5k(256kHz/fC)
R32 =
10k(256kHz/fC)
6.04k(256kHz/fC)
6.19k(256kHz/fC)
Note 1: The resistor values listed in this table provide good approximations of the listed transfer functions. For the
optimal resistor values, higher gain or other transfer functions, use FilterCAD Version 3.0 (or newer) or contact the
Linear Technology Filter Applications group for assistance.
14
www.BDTIC.com/Linear
156323fa
LTC1563-2/LTC1563-3
U
TYPICAL APPLICATIO S
±5V, 2.3mA Supply Current, 20kHz, 4th Order,
0.5dB Ripple Chebyshev Lowpass Filter
Frequency Response
10
LTC1563-2
2
3
169k
4
5
274k
274k
6
VIN
7
8
–5V
16
V+
LP
SA
LPB
NC
NC
INVA
15
13
SB
AGND
NC
V–
0
–10
0.1µF
–20
95.3k
12
NC
LPA
162k
14
INVB
NC
VOUT
5V
GAIN (dB)
1
11
10
EN
–40
–50
–60
162k
9
–30
–70
ENABLE
–80
0.1µF
1563 TA03
–90
1
10
FREQUENCY (kHz)
100
1563 TA04
Single 3.3V, 2mA Supply Current, 20kHz 8th Order Butterworth Lowpass Filter
3.3V
0.1µF
LTC1563-2
1
2
3
115k
4
5
137k
6
7
115k
VIN
8
LP
SA
LPB
NC
NC
INVA
NC
INVB
NC
LPA
SB
AGND
NC
V–
EN
LTC1563-2
210k
16
V+
1
82.5k
15
2
3
14
75k
196k
13
4
210k
6
7
10
82.5k
9
LP
V+
SA
LPB
NC
NC
INVA
5
12
11
0.1µF
8
INVB
NC
NC
LPA
SB
AGND
NC
V–
EN
16
15
158k
VOUT
14
13
100k
12
11
10
9
158k
0.1µF
0.1µF
1563 TA05
ENABLE
Frequency Response
10
0
–10
GAIN (dB)
–20
–30
–40
–50
–60
–70
–80
–90
1
10
FREQUENCY (kHz)
100
1563 TA06
www.BDTIC.com/Linear
156323fa
15
LTC1563-2/LTC1563-3
U
TYPICAL APPLICATIO S
100kHz, 6th Order Pseudo-Butterworth
Frequency Response
3.3V
2
3
R31
VIN
RA1 3.16k
RB1 29.4k
C11
560pF
17.8k
R21
32.4k
4
5
6
7
8
16
V+
LP
SA
LPB
NC
NC
INVA
INVB
NC
NC
LPA
SB
AGND
NC
V–
EN
15
0
R22
28.7k
–10
–20
VOUT
14
13
R32
12
20.5k
GAIN (dB)
1
10
0.1µF
LTC1563-2
11
–30
–40
–50
–60
10
–70
9
–80
–90
0.1µF
RA2 3.16k
–100
10k
RB2 25.5k
100k
FREQUENCY (Hz)
C12
560pF
1M
1563 TA07a
1563 TA07
TEXTBOOK BUTTERWORTH
PSEUDO-BUTTERWORTH
fO1 = 100kHz
Q1 = 1.9319
fO1 = 100kHz
Q1 = 1.9319
fO2 = 100kHz
Q2 = 0.7071
fO2 = 100kHz
Q2 = 0.7358
fO3 = 100kHz
Q3 = 0.5176
fO3 = 100kHz
Real Poles
fO4 = 100kHz
Real Poles
The complex, 2nd order section of the textbook design
with the lowest Q is replaced with two real first order poles.
The Q of another section is slightly altered such that the
final filter’s response is indistinguisable from a textbook
Butterworth response.
Other Pseudo Filter Response Coefficients (All fO Are Normalized for a 1Hz Filter Cutoff)
BESSEL
0.1dB RIPPLE CHEBYSHEV
0.5dB RIPPLE CHEBYSHEV
TRANSITIONAL GAUSSIAN TO 12dB
TRANSITIONAL GAUSSIAN TO 6dB
f O1
1.9070
1.0600
1.0100
2.1000
1.5000
Q1
1.0230
3.8500
5.3000
2.2000
2.8500
f O2
1.6910
0.8000
0.7200
1.2500
1.0500
Q2
0.6110
1.0000
1.2000
0.8000
0.9000
f O3
1.6060
0.6000
0.5000
1.2500
0.9000
f O4
1.6060
1.0000
0.8000
1.2500
0.9000
The fO and Q values listed above can be entered in
FilterCAD’s Enhanced Design window as a custom response filter. After entering the coefficients, FilterCAD will
produce a schematic of the circuit. The procedure is as
follows:
1. After starting FilterCAD, select the Enhanced Design
window.
2. Select the Custom Response and set the custom FC to
1Hz.
3. In the Coefficients table, go to the Type column and click
on the types listed and set the column with two LP types
and two LP1 types. This sets up a template of a 6th order
filter with two 2nd order lowpass sections and two 1st
order lowpass sections.
16
4. Enter the fO and Q coefficients as listed above. For a
Butterworth filter, use the same coefficients as the
example circuit above except set all of the fO to 1Hz.
5. Set the custom FC to the desired cutoff frequency. This
will automatically multiply all of the fO coefficients. You
have now finished the design of the filter and you can
click on the frequency response or step response
buttons to verify the filter’s response.
6. Click on the Implement button to go on to the filter
implementation stage.
7. In the Enhanced Implement window, click on the Active
RC button to choose the LTC1563-2 part. You are now
done with the filter’s implementation. Click on the
schematic button to view the resulting circuit.
www.BDTIC.com/Linear
156323fa
LTC1563-2/LTC1563-3
U
TYPICAL APPLICATIO S
22kHz, 5th Order, 0.1dB Ripple Chebyshev Lowpass Filter
Driving the LTC1604, 16-Bit ADC
5V
0.1µF
LTC1563-2
2
3
RB1 215k
C11
560pF
–5V
82.5k
R21
5
243k
7
6
8
SA
LPB
NC
NC
INVA
INVB
NC
NC
LPA
SB
AGND
NC
V–
10µF
16
15
R22
137k
49.9Ω
560pF
14
13
R32
12
78.7k
2.2µF
47µF
11
10
EN
0.1µF
9
5V
R12 137k
+
10µF
1 A + LTC1604
AVDD
IN
2 A –
AV
IN
DD
3 V
SHDN
REF
4 REFCOMP
CS
5 AGND
CONVST
6 AGND
RD
7 AGND
BUSY
8 AGND
+
35
5V
10Ω
36
33
10µF
32
µP
CONTROL
LINES
31
30
27
11 TO 26
16-BIT
PARALLEL BUS
9 DV
DD
10 DGND
OVDD
34 V
SS
OGND
29
28
5V OR 3V
+
10µF
–5V
10µF
+
1563 TA08
4096 Point FFT of the Output Data
0
fSAMPLE = 292.6kHz
fIN = 20kHz
SINAD = 85dB
THD = –91.5dB
–20
–40
AMPLITUDE (dB)
VIN
RA1 26.7k
4
V+
+
R31
LP
+
1
–60
–80
–100
–120
–140
0
36.58
73.15
109.73
FREQUENCY (kHz)
146.30
1563 TA08a
www.BDTIC.com/Linear
156323fa
17
LTC1563-2/LTC1563-3
U
TYPICAL APPLICATIO S
50kHz Wideband Bandpass
4th Order Bessel Lowpass at 128kHz with Two Highpass Poles at 11.7kHz Yields a Wideband Bandpass Centered at 50kHz
10
5V
LTC1563-3
2
3
R31
C11
680pF
R11
20k
VIN
4
20k
R21
5
20k
7
6
8
–5V
LP
V+
SA
LPB
NC
INVA
NC
INVB
NC
NC
LPA
SB
AGND
NC
V–
EN
0.1µF
16
15
0
R22
20k
–10
VOUT
14
13
R32
12
20k
GAIN (dB)
1
11
–20
–30
–40
10
R12
20k
9
–50
C12
680pF
0.1µF
–60
1k
1563 TA09
10k
100k
FREQUENCY (Hz)
1M
1563 TA09a
To design these wideband bandpass filters with the
LTC1563, start with a 4th order lowpass filter and add two
highpass poles with the input, AC coupling capacitors. The
lowpass cutoff frequency and highpass pole frequencies
depend on the specific application. Some experimentation
of lowpass and highpass frequencies is required to achieve
the desired response. FilterCAD does not directly support
this configuration. Use the custom design window in
FilterCAD get the desired response and then use FilterCAD
to give the schematic for the lowpass portion of the filter.
Calculate the two highpass poles using the following
formulae:
1
1
fO (HPA ) =
, fO (HPB ) =
2 • π • R11• C11
2 • π • R12 • C12
The design process is as follows:
1. After starting FilterCAD, select the Enhanced Design
window.
2. Choose a 4th order Bessel or Butterworth lowpass filter
response and set the cutoff frequency to the high
frequency corner of the desired bandpass.
3. Click on the custom response button. This copies the
lowpass coefficients into the custom design Coefficients table.
4. In the Coefficients table, the first two rows are the LP
Type with the fO and Q as previously defined. Go to the
third and fourth rows and click on the Type column
(currently a hyphen is in this space). Change the Type
of each of these rows to type HP1. This sets up a
template of a 6th order filter with two 2nd order lowpass
sections and two 1st order highpass sections.
5. Change the frequency of the highpass (HP1) poles to
get the desired frequency response.
6. You may have to perform this loop several times before
you close in on the correct response.
7. Once you have reached a satisfactory response, note
the highpass pole frequencies. The HP1 highpass poles
must now be removed from the Custom design coefficients table. After removing the highpass poles, click on
the Implement button to go on to the filter implementation stage.
8. In the Enhanced Implement window, click on the Active
RC button and choose the LTC1563-2 part. Click on the
schematic button to view the resulting circuit.
9. You now have the schematic for the 4th order lowpass
part of the design. Now calculate the capacitor values
from the following formulae:
C11 =
18
1
1
, C12 =
2 • π • R11• fO (HPA )
2 • π • R12 • fO (HPB )
www.BDTIC.com/Linear
156323fa
LTC1563-2/LTC1563-3
U
TYPICAL APPLICATIO S
150kHz, 0.5dB Ripple, 4th Order Chebyshev with 10dB of DC Gain
20
5V
LTC1563-2
2
3
R31
R11
24.3k
VIN
4
9.76k
R21
5
6
76.8k
7
8
–5V
V+
LP
SA
LPB
NC
NC
INVA
INVB
NC
NC
LPA
SB
AGND
NC
V–
EN
16
0
R22
21k
15
–10
14
VOUT
13
R32
12
12.7k
GAIN (dB)
1
10
0.1µF
–20
–30
–40
11
10
–50
R12
21k
9
–60
–70
10k
0.1µF
100k
FREQUENCY (Hz)
1563 TA10
1M
1563 TA10a
U
PACKAGE DESCRIPTIO
Dimensions in inches (millimeters) unless otherwise noted.
GN Package
16-Lead Plastic SSOP (Narrow 0.150)
(LTC DWG # 05-08-1641)
.189 – .196*
(4.801 – 4.978)
.045 ±.005
16 15 14 13 12 11 10 9
.254 MIN
.009
(0.229)
REF
.150 – .165
.229 – .244
(5.817 – 6.198)
.0165 ± .0015
.150 – .157**
(3.810 – 3.988)
.0250 BSC
RECOMMENDED SOLDER PAD LAYOUT
1
.015 ± .004
× 45°
(0.38 ± 0.10)
.007 – .0098
(0.178 – 0.249)
2 3
4
5 6
7
.0532 – .0688
(1.35 – 1.75)
8
.004 – .0098
(0.102 – 0.249)
0° – 8° TYP
.016 – .050
(0.406 – 1.270)
NOTE:
1. CONTROLLING DIMENSION: INCHES
INCHES
2. DIMENSIONS ARE IN
(MILLIMETERS)
.008 – .012
(0.203 – 0.305)
TYP
.0250
(0.635)
BSC
GN16 (SSOP) 0204
3. DRAWING NOT TO SCALE
*DIMENSION DOES NOT INCLUDE MOLD FLASH. MOLD FLASH
SHALL NOT EXCEED 0.006" (0.152mm) PER SIDE
**DIMENSION DOES NOT INCLUDE INTERLEAD FLASH. INTERLEAD
FLASH SHALL NOT EXCEED 0.010" (0.254mm) PER SIDE
www.BDTIC.com/Linear
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 representation that the interconnection of its circuits as described herein will not infringe on existing patent rights.
156323fa
19
LTC1563-2/LTC1563-3
U
TYPICAL APPLICATIO S
Single Supply, 10kHz, Bandpass Filter
Maximum Fcenter = 120kHz (–3dB Bandwidth = Fcenter/10)
V
LTC1563-2
2
VIN
3
R1
31.6k
4
5
R2
4.99k
6
7
0.1µF
8
LP
SA
NC
INVA
NC
LPA
AGND
V–
3
0.1µF
16
V+
15
LPB
14
NC
13
INVB
12
NC
11
SB
10
NC
9
EN
0
R3
200k
–3
VOUT
–6
GAIN (dB)
1
Frequency Response
+
R4
200k
–9
–12
–15
–18
–21
–24
5
1563 TA11
GAIN AT fCENTER = 31.6k
R1
R2 = 4.99k
7.5
MAXIMUM GAIN = 120kHz/fCENTER
10
12.5
15
FREQUENCY (kHz)
1021
fCENTER • (fCENTER2 + 5 • 1011)
Single Supply, 100kHz, Elliptic Lowpass Filter
Maximum Fcutoff = 120kHz
Frequency Response
VOUT
R1
32.4k
R4
32.4k
2
R3
15k
3
R2
32.4k
5
4
6
7
0.1µF
8
LP
SA
NC
INVA
NC
LPA
AGND
V–
0
0.1µF
16
V+
15
LPB
14
NC
13
INVB
12
NC
11
SB
10
NC
9
EN
–6
R5
32.4k
–12
–18
GAIN (dB)
1
6
V+
LTC1563-2
VIN
20
1563 TA11a
R3 = R4 = R
R=
17.5
–24
–30
–36
R6
21k
–42
CIN
27pF
–48
–54
–60
1K
1563 TA12
10K
100K
FREQUENCY (Hz)
PASSBAND GAIN = 0dB
STOPBAND ATTENUATION = 26dB AT 1.5X fCUTOFF
CIN = 27pF R2 = R4 = R5 = R1
9
R1 = 3.24 • 10
fCUTOFF
R3 = R1
2.16
1M
1563 TA12a
R6 = R1
1.54
RELATED PARTS
PART NUMBER
DESCRIPTION
COMMENTS
LTC1560-1
5-Pole Elliptic Lowpass, fC = 1MHz/0.5MHz
No External Components, SO-8
LTC1562
Universal Quad 2-Pole Active RC
10kHz < fO < 150kHz
LTC1562-2
Universal Quad 2-Pole Active RC
20kHz < fO < 300kHz
LTC1569-6
Low Power 10-Pole Delay Equalized Elliptic Lowpass
fC < 80kHz, One Resistor Sets fC, SO-8
LTC1569-7
10-Pole Delay Equalized Elliptic Lowpass
fC < 256kHz, One Resistor Sets fC, SO-8
LTC1565-31
650kHz Continuous Time, Linear Phase Lowpass
fC = 650kHz, Differential In/Out
LTC1568
Very Low Noise 4th Order Filter Building Block
fC < 10MHz
20
www.BDTIC.com/Linear
Linear Technology Corporation
156323fa
LT 1205 REV A • PRINTED IN USA
1630 McCarthy Blvd., Milpitas, CA 95035-7417
(408) 432-1900 FAX: (408) 434-0507
●
●
www.linear.com
© LINEAR TECHNOLOGY CORPORATION 2005