15633I

Linear Technology

Active RC, 4th Order Lowpass Filter Family

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LTC1563-2_1 LINER

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■ 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 FilterCAD TM ■ 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 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: R = 10k (256kHz/f C); fC = Cutoff Frequency where fC is the desired cutoff frequency. For many appli- cations, 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 re- duced 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). ■ Discrete RC Active Filter Replacement ■ Antialiasing Filters ■ Smoothing or Reconstruction Filters ■ Linear Phase Filtering for Data Communication ■ Phase Locked Loops Single 3.3V, 256Hz to 256kHz Butterworth Lowpass Filter Active RC, 4th Order Lowpass Filter Family , LTC and LT are registered trademarks of Linear Technology Corporation. 0.1µF 3.3V VOUT VIN R RR R R R fC = 256kHz 1563 TA01 LTC1563-2 0.1µF LP SA NC INVA NC LPA AGND V LPB NC INVB NC SB NC EN 10k R() FREQUENCY (Hz) 10k1k100 GAIN (dB) –10 –20 –30 –40 –50 –60 –70 –80 100k 1M

1563 TA02

R = 10M fC = 256Hz R = 10k fC = 256kHz Frequency Response APPLICATIO SU

FEATURES

FilterCAD is trademark of Linear Technology Corporation. All other trademarks are the property of their respective owners.

TJMAX = 150°C, θJA = 135°C/ W ORDER PART Maximum Input Voltage at Operating Temperature Range (Note 1) ABSOLUTE MAXIMUM RATINGSW WW U PACKAGE/ORDER INFORMATIONW UU

ELECTRICAL CHARACTERISTICS

NOTE: PINS LABELED NC ARE NOT CONNECTED INTERNALLY AND SHOULD BE CONNECTED TO THE SYSTEM GROUND 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. Consult LTC Marketing for Military grade parts. PARAMETER CONDITIONS MIN TYP MAX UNITS Specifications for Both LTC1563-2 and LTC1563-3 Total Supply Voltage (VS), HS Mode ● 31 1 V Total Supply Voltage (VS), LP Mode ● 2.7 11 V Output Voltage Swing High (LPB Pin) V S = 3V, fC = 25.6kHz, RFIL = 100k, RL = 10k to GND ● 2.9 2.95 V HS Mode V S = 4.75V, fC = 25.6kHz, RFIL = 100k, RL = 10k to GND ● 4.55 4.7 V VS = ± 5V, fC = 25.6kHz, RFIL = 100k, RL = 10k to GND ● 4.8 4.9 V Output Voltage Swing Low (LPB Pin) V S = 3V, fC = 25.6kHz, RFIL = 100k, RL = 10k to GND ● 0.015 0.05 V HS Mode V S = 4.75V, fC = 25.6kHz, RFIL = 100k, RL = 10k to GND ● 0.02 0.05 V VS = ± 5V, fC = 25.6kHz, RFIL = 100k, RL = 10k to GND ● – 4.95 – 4.9 V Output Swing High (LPB Pin) V S = 2.7V, fC = 25.6kHz, RFIL = 100k, RL = 10k to GND ● 2.6 2.65 V LP Mode V S = 4.75V, fC = 25.6kHz, RFIL = 100k, RL = 10k to GND ● 4.55 4.65 V VS = ± 5V, fC = 25.6kHz, RFIL = 100k, RL = 10k to GND ● 4.8 4.9 V Output Swing Low (LPB Pin) V S = 2.7V, fC = 25.6kHz, RFIL = 100k, RL = 10k to GND ● 0.01 0.05 V LP Mode V S = 4.75V, fC = 25.6kHz, RFIL = 100k, RL = 10k to GND ● 0.015 0.05 V VS = ± 5V, fC = 25.6kHz, RFIL = 100k, RL = 10k to GND ● – 4.95 – 4.9 V DC Offset Voltage, HS Mode V S = 3V, fC = 25.6kHz, RFIL = 100k ● ±1.5 ± 3m V (Section A Only) V S = 4.75V, fC = 25.6kHz, RFIL = 100k ● ±1.0 ± 3m V VS = ± 5V, fC = 25.6kHz, RFIL = 100k ● ±1.5 ± 3m V DC Offset Voltage, LP Mode V S = 2.7V, fC = 25.6kHz, RFIL = 100k ● ± 2 ± 6m V (Section A Only) V S = 4.75V, fC = 25.6kHz, RFIL = 100k ● ± 2 ± 6m V VS = ± 5V, fC = 25.6kHz, RFIL = 100k ● ± 2 ± 7m V DC Offset Voltage, HS Mode V S = 3V, fC = 25.6kHz, RFIL = 100k ● ±1.5 ± 3m V (Input to Output, Sections A, B Cascaded) V S = 4.75V, fC = 25.6kHz, RFIL = 100k ● ±1.0 ± 3m V VS = ± 5V, fC = 25.6kHz, RFIL = 100k ● ±1.5 ± 3m V 15632 15633 15632I 15633I GN PART MARKING 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/

PARAMETER CONDITIONS MIN TYP MAX UNITS DC Offset Voltage, LP Mode V S = 2.7V, fC = 25.6kHz, RFIL = 100k ● ± 2 ± 7m V (Input to Output, Sections A, B Cascaded) V S = 4.75V, fC = 25.6kHz, RFIL = 100k ● ± 2 ± 7m V VS = ± 5V, fC = 25.6kHz, RFIL = 100k ● ± 2 ± 8m V DC Offset Voltage Drift, HS Mode V S = 3V, fC = 25.6kHz, RFIL = 100k ● 10 µV/°C (Input to Output, Sections A, B Cascaded) V S = 4.75V, fC = 25.6kHz, RFIL = 100k ● 10 µV/°C VS = ± 5V, fC = 25.6kHz, RFIL = 100k ● 10 µV/°C DC Offset Voltage Drift, LP Mode V S = 2.7V, fC = 25.6kHz, RFIL = 100k ● 10 µV/°C (Input to Output, Sections A, B Cascaded) V S = 4.75V, fC = 25.6kHz, RFIL = 100k ● 10 µV/°C VS = ± 5V, fC = 25.6kHz, RFIL = 100k ● 10 µV/°C Power Supply Current, HS Mode V S = 3V, fC = 25.6kHz, RFIL = 100k ● 8.0 14 mA VS = 4.75V, fC = 25.6kHz, RFIL = 100k ● 10.5 17 mA VS = ± 5V, fC = 25.6kHz, RFIL = 100k ● 15 23 mA Power Supply Current, LP Mode V S = 2.7V, fC = 25.6kHz, RFIL = 100k ● 1.0 1.8 mA VS = 4.75V, fC = 25.6kHz, RFIL = 100k ● 1.4 2.5 mA VS = ± 5V, fC = 25.6kHz, RFIL = 100k ● 2.3 3.5 mA Shutdown Mode Supply Current V S = 4.75V, fC = 25.6kHz, RFIL = 100k ● 12 0 µA EN Input V S = 3V ● 0.8 V Logic Low Level V S = 4.75V ● 1V VS = ± 5V ● 1V EN Input V S = 3V ● 2.5 V Logic High Level V S = 4.75V ● 4.3 V VS = ± 5V ● 4.4 V LP V S = 3V ● 0.8 V Logic Low Level V S = 4.75V ● 1V VS = ± 5V ● 1V LP V S = 3V ● 2.5 V Logic High Level V S = 4.75V ● 4.3 V VS = ± 5V ● 4.4 V LTC1563-2 Transfer Function Characteristics Cutoff Frequency Range, fC VS = 3V ● 0.256 256 kHz HS Mode V S = 4.75V ● 0.256 256 kHz (Note 2) V S = ± 5V ● 0.256 256 kHz Cutoff Frequency Range, fC VS = 2.7V ● 0.256 25.6 kHz LP Mode V S = 4.75V ● 0.256 25.6 kHz (Note 2) V S = ± 5V ● 0.256 25.6 kHz Cutoff Frequency Accuracy, HS Mode V S = 3V, RFIL = 100k ● –2.0 ±1.5 3.5 % Cutoff Frequency Accuracy, HS Mode V S = 3V, RFIL = 10k ● –5 ±1.5 2.5 % fC = 256kHz V S = 4.75V, RFIL = 10k ● –5 ±1.5 2.5 % Cutoff Frequency Accuracy, LP Mode V S = 2.7V, RFIL = 100k ● –3 ±1.5 3 % fC = 25.6kHz V S = 4.75V, RFIL = 100k ● –3 ±1.5 3 % VS = ± 5V, RFIL = 100k ● –3 ±1.5 3 % Cutoff Frequency Temperature Coefficient (Note 3) ● ±1 ppm/ °C 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 MIN TYP MAX UNITS Stopband Gain, HS Mode, fC = 25.6kHz Test Frequency = 51.2kHz (2 • f C) ● – 24 – 21.5 d B VS = 4.75V, RFIL = 100k Test Frequency = 102.4kHz (4 • f C) ● –4 8 –4 6 d B Passband Gain, HS Mode, fC = 256kHz Test Frequency = 25.6kHz (0.1 • f C) ● –0.2 0 0.2 dB VS = 4.75V, RFIL = 10k Test Frequency = 128kHz (0.5 • f C) ● –0.5 0 0.5 dB Stopband Gain, HS Mode, fC = 256kHz Test Frequency = 400kHz (1.56 • f C) ● – 15.7 –13.5 dB VS = 4.75V, RFIL = 10k Test Frequency = 500kHz (1.95 • f C) ● – 23.3 – 21.5 dB Stopband Gain, LP Mode, fC = 25.6kHz Test Frequency = 51.2kHz (2 • f C) ● –2 4 –2 2 d B VS = 4.75V, RFIL = 100k Test Frequency = 102.4kHz (4 • f C) ● – 48 – 46.5 dB LTC1563-3 Transfer Function Characteristics Cutoff Frequency Range, fC VS = 3V ● 0.256 256 kHz HS Mode V S = 4.75V ● 0.256 256 kHz (Note 2) V S = ± 5V ● 0.256 256 kHz Cutoff Frequency Range, fC VS = 2.7V ● 0.256 25.6 kHz LP Mode V S = 4.75V ● 0.256 25.6 kHz (Note 2) V S = ± 5V ● 0.256 25.6 kHz Cutoff Frequency Accuracy, HS Mode V S = 3V, RFIL = 100k ● –3 ± 2 5.5 % fC = 25.6kHz V S = 4.75V, RFIL = 100k ● –3 ± 2 5.5 % VS = ± 5V, RFIL = 100k ● –3 ± 2 5.5 % Cutoff Frequency Accuracy, HS Mode V S = 3V, RFIL = 10k ● –3 ± 26 % fC = 256kHz V S = 4.75V, RFIL = 10k ● –3 ± 26 % VS = ± 5V, RFIL = 10k ● –3 ± 26 % Cutoff Frequency Accuracy, LP Mode V S = 2.7V, RFIL = 100k ● –4 ± 37 % fC = 25.6kHz V S = 4.75V, RFIL = 100k ● –4 ± 37 % VS = ± 5V, RFIL = 100k ● –4 ± 37 % Cutoff Frequency Temperature Coefficient (Note 3) ● ±1 ppm/ °C Stopband Gain, HS Mode, fC = 25.6kHz Test Frequency = 51.2kHz (2 • f C) ● –13.6 –10 dB VS = 4.75V, RFIL = 100k Test Frequency = 102.4kHz (4 • f C) ● – 34.7 – 31 dB Stopband Gain, HS Mode, fC = 256kHz Test Frequency = 400kHz (1.56 • f C) ● –8.3 –6 dB VS = 4.75V, RFIL = 10k Test Frequency = 500kHz (1.95 • f C) ● – 13 –10.5 dB Stopband Gain, LP Mode, fC = 25.6kHz Test Frequency = 51.2kHz (2 • f C) ● – 13.6 –11 dB VS = 4.75V, RFIL = 100k Test Frequency = 102.4kHz (4 • f C) ● – 34.7 – 32 dB 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 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. 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.

TYPICAL PERFOR A CE CHARACTERISTICSUW Output Voltage Swing High vs Load Resistance Output Voltage Swing High vs Load Resistance Output Voltage Swing High vs Load Resistance Output Voltage Swing Low vs Load Resistance Output Voltage Swing Low vs Load Resistance Output Voltage Swing Low vs Load Resistance THD + Noise vs Input Voltage THD + Noise vs Input Voltage THD + Noise vs Input Voltage LOAD RESISTANCE—LOAD TO GROUND ( Ω) 100 OUTPUT VOLTAGE (V) 3.4 3.2 3.0 2.8 2.6 2.4 2.2 2.0 1k 10k 100k

1563 G01

VS = SINGLE 3.3V LP MODE HS MODE LOAD RESISTANCE—LOAD TO GROUND ( Ω) 100 OUTPUT VOLTAGE (V) 5.5 5.0 4.5 4.0 3.5 3.0 2.5 1k 10k 100k

1563 G02

VS = SINGLE 5V LOAD RESISTANCE—LOAD TO GROUND ( Ω) 100 OUTPUT VOLTAGE (V) 5.5 5.0 4.5 4.0 3.5 3.0 2.5 1k 10k 100k

1563 G03

VS = ±5V LOAD RESISTANCE—LOAD TO GROUND ( Ω) 100 OUTPUT VOLTAGE (V) 0.025 0.020 0.015 0.010 0.005 1k 10k 100k

1563 G04

VS = SINGLE 3.3V LOAD RESISTANCE—LOAD TO GROUND ( Ω) 100 OUTPUT VOLTAGE (V) 0.025 0.020 0.015 0.010 0.005 1k 10k 100k

1563 G05

VS = SINGLE 5V LOAD RESISTANCE—LOAD TO GROUND ( Ω) 100 OUTPUT VOLTAGE (V) –4.3 –4.4 –4.5 –4.6 –4.7 –4.8 –4.9 –5.0 1k 10k 100k

1563 G06

VS = ± 5V HS MODE LP MODE INPUT VOLTAGE (VP-P) 0.1 (THD + NOISE)/SIGNAL (dB) –40 –50 –60 –70 –80 –90 –100 11 0

1563 G07

3.3V SUPPLY 5V SUPPLY ±5V SUPPLY fC = 25.6kHz LOW POWER MODE fIN = 5kHz INPUT VOLTAGE (VP-P) 0.1 (THD + NOISE)/SIGNAL (dB) –40 –50 –60 –70 –80 –90 –100 11 0

1563 G08

3.3V SUPPLY 5V SUPPLY ±5V SUPPLY fC = 25.6kHz HIGH SPEED MODE fIN = 5kHz INPUT VOLTAGE (VP-P) 0.1 (THD + NOISE)/SIGNAL (dB) –40 –50 –60 –70 –80 –90 –100 11 0

1563 G09

3.3V SUPPLY 5V SUPPLY ±5V SUPPLY fC = 256kHz HIGH SPEED MODE fIN = 50kHz

THD + Noise vs Input Frequency THD + Noise vs Input Frequency THD + Noise vs Input Frequency THD + Noise vs Input Frequency THD + Noise vs Input Frequency THD + Noise vs Input Frequency THD + Noise vs Input Frequency THD + Noise vs Input Frequency THD + Noise vs Input Frequency INPUT FREQUENCY (kHz) (THD + NOISE)/SIGNAL (dB)

1563 G10

–60 –70 –80 –90 –100 1VP-P 2VP-P VS = SINGLE 3.3V LOW POWER MODE fC = 25.6kHz INPUT FREQUENCY (kHz) (THD + NOISE)/SIGNAL (dB)

1563 G11

–60 –70 –80 –90 –100 1VP-P 2VP-P VS = SINGLE 3.3V HIGH SPEED MODE fC = 25.6kHz –40 –50 –60 –70 –80 –90 –100 INPUT FREQUENCY (kHz) 1 10 100

1563 G12

(THD + NOISE)/SIGNAL (dB) 1VP-P 2VP-P VS = SINGLE 3V HIGH SPEED MODE fC = 256kHz INPUT FREQUENCY (kHz) (THD + NOISE)/SIGNAL (dB)

1563 G13

–60 –70 –80 –90 –100 1VP-P 2VP-P 3VP-P VS = SINGLE 5V LOW POWER MODE fC = 25.6kHz INPUT FREQUENCY (kHz) (THD + NOISE)/SIGNAL (dB)

1563 G14

–60 –70 –80 –90 –100 1VP-P 2VP-P 3VP-P VS = SINGLE 5V HIGH SPEED MODE fC = 25.6kHz –40 –50 –60 –70 –80 –90 –100 INPUT FREQUENCY (kHz) 1 10 100

1563 G15

(THD + NOISE)/SIGNAL (dB) 1VP-P 2VP-P 3VP-P VS = SINGLE 5V HIGH SPEED MODE fC = 256kHz INPUT FREQUENCY (kHz) (THD + NOISE)/SIGNAL (dB)

1563 G16

–60 –70 –80 –90 –100 1VP-P 2VP-P 5VP-P VS = ± 5V LOW POWER MODE fC = 25.6kHz INPUT FREQUENCY (kHz) (THD + NOISE)/SIGNAL (dB)

1563 G17

–60 –70 –80 –90 –100 1VP-P 2VP-P 5VP-P VS = ± 5V HIGH SPEED MODE fC = 25.6kHz –40 –50 –60 –70 –80 –90 –100 INPUT FREQUENCY (kHz) 1 10 100

1563 G18

(THD + NOISE)/SIGNAL (dB) 1VP-P 5VP-P 2VP-P VS = ± 5V HIGH SPEED MODE fC = 256kHz TYPICAL PERFOR A CE CHARACTERISTICSUW

THD + Noise vs Output Load THD + Noise vs Output Load Output Voltage Noise vs Cutoff Frequency THD + Noise vs Output Load THD + Noise vs Output Load Stopband Gain vs Input Frequency Crosstalk Rejection vs Frequency Crosstalk Rejection vs Frequency OUTPUT LOAD RESISTANCE—LOAD TO GROUND (k Ω) 0123456789 1 0 (THD + NOISE)/SIGNAL (dB)

1563 G19

–70 –75 –80 –85 –90 –95 –100 LP MODE, 3VP-P SIGNAL LP MODE, P-P SIGNAL HS MODE, P-P SIGNAL HS MODE, P-P SIGNAL VS = SINGLE 5V fC = 25.6kHz fIN = 5kHz OUTPUT LOAD RESISTANCE—LOAD TO GROUND (k Ω) 0123456789 1 0 (THD + NOISE)/SIGNAL (dB)

1563 G20

–70 –75 –80 –85 –90 –95 –100 VS = SINGLE 5V HIGH SPEED MODE fC = 256kHz fIN = 20kHz, 50kHz 3VP-P, 20kHz3VP-P, 50kHz 2VP-P, 50kHz 2VP-P, 20kHz fC (Hz) TOTAL INTEGRATED NOISE (µVRMS) 0.1 10 100 1000

1563 G21

TA = 25°C HS MODE LP MODE OUTPUT LOAD RESISTANCE—LOAD TO GROUND (k Ω) 0123456789 1 0 (THD + NOISE)/SIGNAL (dB)

1563 G22

–70 –75 –80 –85 –90 –95 –100 LP MODE, 5VP-P SIGNAL LP MODE, P-P SIGNAL HS MODE, P-P SIGNAL HS MODE, P-P SIGNAL VS = ± 5V fC = 25.6kHz fIN = 5kHz –70 –75 –80 –85 –90 –95 –100 OUTPUT LOAD RESISTANCE—LOAD TO GROUND (k Ω) 0123456789 1 0 (THD + NOISE)/SIGNAL (dB)

1563 G23

5VP-P, 50kHz 2VP-P, 20kHz 2VP-P, 20kHz 2VP-P, 50kHz VS = ± 5V HIGH SPEED MODE fC = 256kHz fIN = 20kHz, 50kHz FREQUENCY (kHz) CROSSTALK (dB) –60 –70 –80 –90 –100 –110 10 100

1563 G25

f C = 25.6kHz HS OR LP MODE FREQUENCY (Hz) 1k 10k 100k 1M

1563 G26

CROSSTALK (dB) –60 –70 –80 –90 –100 –110 DUAL SECOND ORDER BUTTERWORTH f C = 256kHz HIGH SPEED MODE FREQUENCY (Hz) GAIN (dB) –10 –20 –30 –40 –50 –60 –70 –80 –90 10k 1M 10M 100M

1563 G24

fC = 256kHz TYPICAL PERFOR A CE CHARACTERISTICSUW

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 fre- quency, 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. 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 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. NC (Pins 3, 5, 10, 12, 14): These pins are not connected internally. For best performance, they should be con- nected to ground. 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 fre- quency response of the filter sections. For these reasons, printed circuit connections to the INV pins must be kept as short as possible. PIN FUNCTIONSUU U 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 5k Ω and 20pF. Refer to the Applications Information section for more details on output loading effects. 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. V –, V + (Pins 8, 16): The V – and V + pins should be bypassed with 0.1 µF 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 sup- plies 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. 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 compo- nents around the inactive part. 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.

V LPB NC INVB NC SB NC EN 0.1µF LTC1563-X ANALOG GROUND PLANE DIGITAL GROUND PLANE (IF ANY)

1563 PF01

0.1µF PIN FUNCTIONSUU U LP SA NC INVA NC LPA AGND V LPB NC INVB NC SB NC EN0.1µF LTC1563-X ANALOG GROUND PLANE DIGITAL GROUND PLANE (IF ANY)

1563 PF02

0.1µF Dual Supply Power and Ground Connections Single Supply Power and Ground Connections BLOCK DIAGRA W SHUTDOWN SWITCH SHUTDOWN SWITCH EN LP 20k 20k AGND SA LPAINVA R31 R21 R11 C2A AGND VIN 8 1 C1A SB LPB LTC1563-X PATENT PENDING 1563 BD INVB R32 R22 R12 C2B AGNDAGND VOUT C1B

APPLICATIONS INFORMATIONWU UU 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/f where fC is the desired cutoff frequency. For many appli- cations, 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 sec- tions. 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 calcu- lation 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 Applica- tions group for assistance. Cutoff Frequency (f C) and Gain Limitations The LTC563-X has both a maximum f C limit and a mini- mum 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 f C is dictated by the practical limitation of reliably obtaining large valued, precision resistors. As the desired fC decreases, the resistor value required increases. When f C 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 200M Ω of stray, layout related 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 f 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 func- tions, 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.

be divided into resistive effects and capacitive effects. must never drive a long coaxial cable. LTC1563-X, always use a 10x probe. Never use a 1x probe. while a 1x probe’s capacitance can be as high as 150pF. The use of a 1x probe will probably cause oscillation. load is too great, a buffer must be used. alter the transfer function. Capacitance to an AC ground is the most likely problem. the part without any vias in the signal path. layout is possible with smaller resistors.

1653 F01

Figure 1. PC Board Layout single pole sections and odd order filters are easily achieved. stand alone inverting gain single pole filter.

should be much larger than RA1 to minimize the interac- tion 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. DC GAIN = LTC1563-2: C1A = 53.9pF, C1B = 39.2pF LTC1563-3: C1A = 35pF, C1B = 26.8pF –R2 FP = 1 2π • R2 • C1 1563 F02 C1INV S 1/2 LTC1563 LP AGND (OPEN) VOUTVIN Figure 2 RA1 ≈ RB1 R2RB1RA1 R3 CP

1563 F03

RA1 • RB1 RA1 + RB1 FP = 1 ()2π •C P C1INV S 1/2 LTC1563 LP AGND (OPEN) C1INV S 1/2 LTC1563 LP

1563 F04

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 pseudo- Butterworth filter. FilterCAD is a valuable tool for custom filter design and tweaking textbook responses. Figure 3 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 uncon- nected. 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. Figure 4 APPLICATIONS INFORMATIONWU UU

Figure 5. 4th Order Filter Connections (Power Supply, Ground,

1563 F05

1563 F05a

1563 F05b

1563 F05c

Table 1. Resistor Values, Normalized to 256kHz Cutoff Frequency (fC), Figure 5. The Passband Linear Technology Filter Applications group for assistance.

Table 2. Resistor Values, Normalized to 256kHz Cutoff Frequency (fC), Figure 6. The Passband Linear Technology Filter Applications group for assistance.

1563 F06

Figure 6. 4th Order Filter Connections (Power Supply, Ground,

1563 F06a

1563 F06b

1563 F06c

V LPB NC INVB NC SB NC EN VOUT ENABLE VIN

1563 TA03

169k 95.3k 162k 274k274k 162k 0.1µF LTC1563-2 –5V 0.1µF ± 5V, 2.3mA Supply Current, 20kHz, 4th Order, 0.5dB Ripple Chebyshev Lowpass Filter Frequency Response LP SA NC INVA NC LPA AGND V LPB NC INVB NC SB NC EN VIN ENABLE 115k 196k 82.5k 210k LTC1563-2 LTC1563-2 137k 115k 0.1µF 0.1µF 82.5k LP SA NC INVA NC LPA AGND V LPB NC INVB NC SB NC EN VOUT 3.3V

1563 TA05

0.1µF 0.1µF Single 3.3V, 2mA Supply Current, 20kHz 8th Order Butterworth Lowpass Filter FREQUENCY (kHz) GAIN (dB) –10 –20 –30 –40 –50 –60 –70 –80 –90 10 100

1563 TA06

FREQUENCY (kHz) GAIN (dB) –10 –20 –30 –40 –50 –60 –70 –80 –90 10 100

1563 TA04

100kHz, 6th Order Pseudo-Butterworth Frequency Response TEXTBOOK BUTTERWORTH PSEUDO-BUTTERWORTH fO1 = 100kHz Q1 = 1.9319 f O1 = 100kHz Q1 = 1.9319 fO2 = 100kHz Q2 = 0.7071 f O2 = 100kHz Q2 = 0.7358 fO3 = 100kHz Q3 = 0.5176 f O3 = 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. The f O and Q values listed above can be entered in FilterCAD’s Enhanced Design window as a custom re- sponse 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 F C 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. 4. Enter the f O and Q coefficients as listed above. For a Butterworth filter, use the same coefficients as the example circuit above except set all of the f O 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. 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 LP SA NC INVA NC LPA AGND V LPB NC INVB NC SB NC EN VOUT 3.3V VIN

1563 TA07

17.8k R32 20.5k R22 28.7k R21 32.4k 0.1µF LTC1563-2 0.1µF C12 560pF C11 560pF RA2 3.16k R B2 25.5k RA1 3.16k R B1 29.4k FREQUENCY (Hz) 10k GAIN (dB) –10 –20 –30 –40 –50 –60 –70 –80 –90 –100 100k 1M

1563 TA07a

4096 Point FFT of the Output Data

22kHz, 5th Order, 0.1dB Ripple Chebyshev Lowpass Filter Driving the LTC1604, 16-Bit ADC LP SA NC INVA NC LPA AGND V LPB NC INVB NC SB NC EN VIN R31 82.5k R32 78.7k R22 137k R21 243k 0.1µF LTC1563-2 0.1µF C11 560pF R12 137k RA1 26.7k R B1 215k + + A IN+ AIN– VREF REFCOMP AGND AGND AGND AGND DV DD DGND V SS

11 TO 26

2.2µF 47µF 49.9Ω 10µF 10µF 10µF 10µF 5V OR 3V 16-BIT PARALLEL BUS µP CONTROL LINES 10Ω –5V –5V 10µF

1563 TA08

–20 –40 –60 –80 –100 –120 –140 0 36.58 73.15 109.73 146.30 FREQUENCY (kHz) AMPLITUDE (dB) fSAMPLE = 292.6kHz fIN = 20kHz SINAD = 85dB THD = –91.5dB

1563 TA08a

4th Order Bessel Lowpass at 128kHz with Two Highpass Poles at 11.7kHz Yields a Wideband Bandpass Centered at 50kHz 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: f HPA RC f HPB RCOO() = () =1 21 1 1 1 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 Coeffi- cients table. 4. In the Coefficients table, the first two rows are the LP Type with the f O 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 coeffi- cients table. After removing the highpass poles, click on the Implement button to go on to the filter implementa- tion 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: C R f HPA C R f HPBOO 11 1 21 1 12 1 21 2= LP SA NC INVA NC LPA AGND V LPB NC INVB NC SB NC EN VOUT VIN

1563 TA09

0.1µF LTC1563-3 0.1µF C12 680pF C11 680pF –5V –10 –20 –30 –40 –50 –60 1k 10k 100k 1M FREQUENCY (Hz) GAIN (dB)

1563 TA09a

150kHz, 0.5dB Ripple, 4th Order Chebyshev with 10dB of DC Gain 16-Lead Plastic SSOP (Narrow 0.150) (LTC DWG # 05-08-1641) PACKAGE DESCRIPTIO U Dimensions in inches (millimeters) unless otherwise noted. 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 represen- tation that the interconnection of its circuits as described herein will not infringe on existing patent rights. TYPICAL APPLICATIO SU GN16 (SSOP) 0204 12 3 4 5 6 7 8 .229 – .244 (5.817 – 6.198) .150 – .157** (3.810 – 3.988) 16 15 14 13 .189 – .196* (4.801 – 4.978) 12 11 10 9 .016 – .050 (0.406 – 1.270) .015 ± .004 (0.178 – 0.249) .0532 – .0688 (1.35 – 1.75) .008 – .012 (0.203 – 0.305) TYP .004 – .0098 (0.102 – 0.249) .0250 (0.635) BSC .009 (0.229) REF .254 MIN RECOMMENDED SOLDER PAD LAYOUT .150 – .165 .0250 BSC.0165 ± .0015 .045 ±.005 *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 INCHES (MILLIMETERS) NOTE: 1. CONTROLLING DIMENSION: INCHES 2. DIMENSIONS ARE IN 3. DRAWING NOT TO SCALE LP SA NC INVA NC LPA AGND V LPB NC INVB NC SB NC EN VOUT VIN –5V

1563 TA10

9.76k R32 12.7k R22 21k R21 76.8k R11 24.3k R12 21k 0.1µF LTC1563-2 0.1µF –10 –20 –30 –40 –50 –60 –70 10k 100k 1M FREQUENCY (Hz) GAIN (dB)

1563 TA10a

Single Supply, 10kHz, Bandpass Filter Maximum Fcenter = 120kHz (–3dB Bandwidth = Fcenter/10) Frequency Response LT 1205 REV A • PRINTED IN USA © LINEAR TECHNOLOGY CORPORATION 2005 Linear Technology Corporation 1630 McCarthy Blvd., Milpitas, CA 95035-7417 (408) 432-1900 ● FAX: (408) 434-0507 ● www.linear.com RELATED PARTS PART NUMBER DESCRIPTION COMMENTS LTC1560-1 5-Pole Elliptic Lowpass, f C = 1MHz/0.5MHz No External Components, SO-8 LTC1562 Universal Quad 2-Pole Active RC 10kHz < f O < 150kHz LTC1562-2 Universal Quad 2-Pole Active RC 20kHz < f O < 300kHz LTC1569-6 Low Power 10-Pole Delay Equalized Elliptic Lowpass f C < 80kHz, One Resistor Sets fC, SO-8 LTC1569-7 10-Pole Delay Equalized Elliptic Lowpass f C < 256kHz, One Resistor Sets fC, SO-8 LTC1565-31 650kHz Continuous Time, Linear Phase Lowpass f C = 650kHz, Differential In/Out LTC1568 Very Low Noise 4 th Order Filter Building Block f C < 10MHz TYPICAL APPLICATIO SU FREQUENCY (Hz) –36 –30GAIN (dB) –24 –12 –18 10K 100K 1M

1563 TA12a

–48 –54 –42 –60 Frequency Response FREQUENCY (kHz) –24 GAIN (dB) –21 –15 –12

1563 TA11a

–18 107.5 17.512.5 20 LP SA NC INVA NC LPA AGND V LPB NC INVB NC SB NC EN VOUT VIN

1563 TA11

31.6k 200k 200kR2 4.99k 0.1µF LTC1563-2 0.1µF GAIN AT fCENTER = MAXIMUM GAIN = 120kHz/fCENTER R2 = 4.99k R3 = R4 = R R = 31.6k 1021 fCENTER • (fCENTER2 + 5 • 1011) Single Supply, 100kHz, Elliptic Lowpass Filter Maximum Fcutoff = 120kHz LP SA NC INVA NC LPA AGND V LPB NC INVB NC SB NC EN VOUT VIN

1563 TA12

32.4k 32.4k 32.4k 21k 15k 32.4k 0.1µF LTC1563-2 CIN 27pF 0.1µF PASSBAND GAIN = 0dB STOPBAND ATTENUATION = 26dB AT 1.5X fCUTOFF CIN = 27pF R2 = R4 = R5 = R1 R1 = R3 = R6 = 3.24 • 109 fCUTOFF 2.16 1.54

Selected Specification

Linear Technology 15633I overview.

Summary

Active RC, 4th Order Lowpass Filter Family

Description

Active RC, 4th Order Lowpass Filter Family

Source title 15633I Datasheet(PDF) - Linear Technology

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