LTC1563-2/LTC1563-3

Extremely Easy to Use--A Single Resistor Value
Sets the Cutoff Frequency (2.56kHz < f

< 256kHz)

Extremely Flexible--Different Resistor Values
Allow Arbitrary Transfer Functions with or without
Gain (2.56kHz < f

< 256kHz)

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: 36

RMS

for f

= 25.6kHz, 60

RMS

for

= 256kHz

Accuracy <

2% (Typ)

DC Offset < 1mV

Cascadable to Form 8th Order Lowpass Filters

Low Power Mode, f

< 25.6kHz, I

SUPPLY

=1mA (Typ)

High Speed Mode, f

< 256kHz, I

SUPPLY

= 10mA (Typ)

Shutdown Mode, I

SUPPLY

= 1

A (Typ)

Continuous Time, Active RC Filter, No Clock

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

); f

= Cutoff Frequency

where f

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 (SO-8 footprint).

Replaces Discrete RC Active Filters and Modules

Antialiasing Filters

Smoothing or Reconstruction Filters

Linear Phase Filtering for Data Communication

Phase Locked Loops

Single 3.3V, 2.56kHz to 256kHz Butterworth Lowpass Filter

Active RC, 4th Order

Lowpass Filter Family

January 2000

FEATURES

DESCRIPTIO

APPLICATIO

TYPICAL APPLICATIO

, LTC and LT are registered trademarks of Linear Technology Corporation.

Final Electrical Specifications

0.1

3.3V

OUT

= 256kHz

1563 TA01

LTC1563-2

INVA

LPA

AGND

LPB

INVB

10k

( )

FREQUENCY (Hz)

10k

GAIN (dB)

100k

1563 TA02

R = 1M
f

= 2.56kHz

R = 10k

= 256kHz

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.

Frequency Response

LTC1563-2/LTC1563-3

LTC1563-2CGN
LTC1563-3CGN
LTC1563-2IGN
LTC1563-3IGN

JMAX

= 150

= 135

C/ W

ORDER PART

NUMBER

Total Supply Voltage (V

to V

) ............................... 11V

Maximum Input Voltage at
Any Pin ....................... (V

0.3V)

+ 0.3V)

Power Dissipation .............................................. 500mW
Operating Temperature Range

LTC1563C ............................................... 0

C to 70

LTC1563I ............................................ 40

C to 85

Storage Temperature Range ................. 65

C to 150

Lead Temperature (Soldering, 10 sec).................. 300

(Note 1)

ABSOLUTE

AXI

RATINGS

PACKAGE/ORDER I

FOR

ATIO

ELECTRICAL CHARACTERISTICS

TOP VIEW

GN PACKAGE

16-LEAD NARROW PLASTIC SSOP

INVA

LPA

AGND

LPB

INVB

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

= Single 4.75V, EN pin to logic "low," Gain = 1, R

FIL

= R11 = R21 = R31 = R12 = R22 = R32, specifications apply to both the high

speed (HS) and low power (LP) modes unless otherwise noted.

Consult factory for Military grade parts.

PARAMETER

CONDITIONS

MIN

TYP

MAX

UNITS

Specifications for Both LTC1563-2 and LTC1563-3

Total Supply Voltage (V

), HS Mode

Total Supply Voltage (V

), LP Mode

2.7

Positive Output Voltage Swing (LPB Pin)

= 3V, f

= 25.6kHz, R

FIL

= 100k, R

= 10k to GND

2.9

2.95

HS Mode

= 4.75V, f

= 25.6kHz, R

FIL

= 100k, R

= 10k to GND

4.55

4.7

5V, f

= 25.6kHz, R

FIL

= 100k, R

= 10k to GND

4.8

4.9

Negative Output Voltage Swing (LPB Pin)

= 3V, f

= 25.6kHz, R

FIL

= 100k, R

= 10k to GND

0.015

0.05

HS Mode

= 4.75V, f

= 25.6kHz, R

FIL

= 100k, R

= 10k to GND

0.02

0.05

5V, f

= 25.6kHz, R

FIL

= 100k, R

= 10k to GND

4.95

4.9

Positive Output Swing (LPB Pin)

= 2.7V, f

= 25.6kHz, R

FIL

= 100k, R

= 10k to GND

2.6

2.65

LP Mode

= 4.75V, f

= 25.6kHz, R

FIL

= 100k, R

= 10k to GND

4.55

4.65

5V, f

= 25.6kHz, R

FIL

= 100k, R

= 10k to GND

4.8

4.9

Negative Output Swing (LPB Pin)

= 2.7V, f

= 25.6kHz, R

FIL

= 100k, R

= 10k to GND

0.01

0.05

LP Mode

= 4.75V, f

= 25.6kHz, R

FIL

= 100k, R

= 10k to GND

0.015

0.05

5V, f

= 25.6kHz, R

FIL

= 100k, R

= 10k to GND

4.95

4.9

DC Offset Voltage, HS Mode

= 3V, f

= 25.6kHz, R

FIL

= 100k

1.5

(Section A Only)

= 4.75V, f

= 25.6kHz, R

FIL

= 100k

1.0

5V, f

= 25.6kHz, R

FIL

= 100k

1.5

DC Offset Voltage, LP Mode

= 2.7V, f

= 25.6kHz, R

FIL

= 100k

(Section A Only)

= 4.75V, f

= 25.6kHz, R

FIL

= 100k

5V, f

= 25.6kHz, R

FIL

= 100k

DC Offset Voltage, HS Mode

= 3V, f

= 25.6kHz, R

FIL

= 100k

1.5

(Input to Output, Sections A, B Cascaded)

= 4.75V, f

= 25.6kHz, R

FIL

= 100k

1.0

5V, f

= 25.6kHz, R

FIL

= 100k

1.5

DC Offset Voltage, LP Mode

= 2.7V, f

= 25.6kHz, R

FIL

= 100k

(Input to Output, Sections A, B Cascaded)

= 4.75V, f

= 25.6kHz, R

FIL

= 100k

5V, f

= 25.6kHz, R

FIL

= 100k

LTC1563-2/LTC1563-3

ELECTRICAL CHARACTERISTICS

PARAMETER

CONDITIONS

MIN

TYP

MAX

UNITS

DC Offset Voltage Drift, HS Mode

= 3V, f

= 25.6kHz, R

FIL

= 100k

(Input to Output, Sections A, B)

= 4.75V, f

= 25.6kHz, R

FIL

= 100k

5V, f

= 25.6kHz, R

FIL

= 100k

DC Offset Voltage Drift, LP Mode

= 2.7V, f

= 25.6kHz, R

FIL

= 100k

(Input to Output, Sections A, B)

= 4.75V, f

= 25.6kHz, R

FIL

= 100k

5V, f

= 25.6kHz, R

FIL

= 100k

AGND Voltage

= 4.75V, f

= 25.6kHz, R

FIL

= 100k

2.35

2.375

2.40

Power Supply Current, HS Mode

= 3V, f

= 25.6kHz, R

FIL

= 100k

8.0

= 4.75V, f

= 25.6kHz, R

FIL

= 100k

10.5

5V, f

= 25.6kHz, R

FIL

= 100k

Power Supply Current, LP Mode

= 2.7V, f

= 25.6kHz, R

FIL

= 100k

1.0

1.8

= 4.75V, f

= 25.6kHz, R

FIL

= 100k

1.4

2.5

5V, f

= 25.6kHz, R

FIL

= 100k

2.3

3.5

Shutdown Mode Supply Current

= 4.75V, f

= 25.6kHz, R

FIL

= 100k

EN Input

= 3V

0.8

Logic Low Level

= 4.75V

EN Input

= 3V

2.5

Logic High Level

= 4.75V

4.3

4.4

= 3V

0.8

Logic Low Level

= 4.75V

= 3V

2.5

Logic High Level

= 4.75V

4.3

4.4

LTC1563-2 Transfer Function Characteristics

Cutoff Frequency Range, f

= 3V

256

kHz

HS Mode

= 4.75V

256

kHz

256

kHz

Cutoff Frequency Range, f

= 2.7V

25.6

kHz

LP Mode

= 4.75V

25.6

kHz

25.6

kHz

Cutoff Frequency Accuracy, HS Mode

= 3V, R

FIL

= 100k

1.5

3.5

= 25.6kHz

= 4.75V, R

FIL

= 100k

1.5

3.5

5V, R

FIL

= 100k

1.5

3.5

Cutoff Frequency Accuracy, HS Mode

= 3V, R

FIL

= 10k

1.5

= 256kHz

= 4.75V, R

FIL

= 10k

1.5

5V, R

FIL

= 10k

1.5

Cutoff Frequency Accuracy, LP Mode

= 2.7V, R

FIL

= 100k

1.5

= 25.6kHz

= 4.75V, R

FIL

= 100k

1.5

5V, R

FIL

= 100k

1.5

Cutoff Frequency Temperature Coefficient

ppm/

Passband Gain, HS Mode, f

= 25.6kHz

Test Frequency = 2.56kHz (0.1 ˇ f

)

0.2

= 4.75V, R

FIL

= 100k

Test Frequency = 12.8kHz (0.5 ˇ f

)

0.3

The

denotes specifications which apply over the full operating temperature range, otherwise specifications are TA = 25

= Single 4.75V, EN pin to logic "low," Gain = 1, R

FIL

= R11 = R21 = R31 = R12 = R22 = R32, specifications apply to both the high

speed (HS) and low power (LP) modes unless otherwise noted.

LTC1563-2/LTC1563-3

ELECTRICAL CHARACTERISTICS

PARAMETER

CONDITIONS

MIN

TYP

MAX

UNITS

Stopband Gain, HS Mode, f

= 25.6kHz

Test Frequency = 51.2kHz (2 ˇ f

)

21.5

d B

= 4.75V, R

FIL

= 100k

Test Frequency = 102.4kHz (4 ˇ f

)

Passband Gain, HS Mode, f

= 256kHz

Test Frequency = 25.6kHz (0.1 ˇ f

)

0.2

= 4.75V, R

FIL

= 10k

Test Frequency = 128kHz (0.5 ˇ f

)

0.5

Stopband Gain, HS Mode, f

= 256kHz

Test Frequency = 400kHz (1.56 ˇ f

)

15.7

13.5

= 4.75V, R

FIL

= 10k

Test Frequency = 500kHz (1.95 ˇ f

)

23.3

21.5

Passband Gain, LP Mode, f

= 25.6kHz

Test Frequency = 2.56kHz (0.1 ˇ f

)

0.25

= 4.75V, R

FIL

= 100k

Test Frequency = 12.8kHz (0.5 ˇ f

)

0.6

0.02

0.6

Stopband Gain, LP Mode, f

= 25.6kHz

Test Frequency = 51.2kHz (2 ˇ f

)

= 4.75V, R

FIL

= 100k

Test Frequency = 102.4kHz (4 ˇ f

)

46.5

LTC1563-3 Transfer Function Characteristics

Cutoff Frequency Range, f

= 3V

256

kHz

HS Mode

= 4.75V

256

kHz

256

kHz

Cutoff Frequency Range, f

= 2.7V

25.6

kHz

LP Mode

= 4.75V

25.6

kHz

25.6

kHz

Cutoff Frequency Accuracy, HS Mode

= 3V, R

FIL

= 100k

5.5

= 25.6kHz

= 4.75V, R

FIL

= 100k

5.5

5V, R

FIL

= 100k

5.5

Cutoff Frequency Accuracy, HS Mode

= 3V, R

FIL

= 10k

= 256kHz

= 4.75V, R

FIL

= 10

5V, R

FIL

= 10k

Cutoff Frequency Accuracy, LP Mode

= 2.7V, R

FIL

= 100k

= 25.6kHz

= 4.75V, R

FIL

= 100k

5V, R

FIL

= 100k

Cutoff Frequency Temperature Coefficient

ppm/

Passband Gain, HS Mode, f

= 25.6kHz

Test Frequency = 2.56kHz (0.1 ˇ f

)

0.2

0.03

0.2

= 4.75V, R

FIL

= 100k

Test Frequency = 12.8kHz (0.5 ˇ f

)

1.0

0.72

0.25

Stopband Gain, HS Mode, f

= 25.6kHz

Test Frequency = 51.2kHz (2 ˇ f

)

13.6

= 4.75V, R

FIL

= 100k

Test Frequency = 102.4kHz (4 ˇ f

)

34.7

Passband Gain, HS Mode, f

= 256kHz

Test Frequency = 25.6kHz (0.1 ˇ f

)

0.2

0.03

0.2

= 4.75V, R

FIL

= 10k

Test Frequency = 128kHz (0.5 ˇ f

)

1.1

0.72

0.5

Stopband Gain, HS Mode, f

= 256kHz

Test Frequency = 400kHz (1.56 ˇ f

)

8.3

= 4.75V, R

FIL

= 10k

Test Frequency = 500kHz (1.95 ˇ f

)

10.5

Passband Gain, LP Mode, f

= 25.6kHz

Test Frequency = 2.56kHz (0.1 ˇ f

)

0.2

0.03

0.2

= 4.75V, R

FIL

= 100k

Test Frequency = 12.8kHz (0.5 ˇ f

)

1.0

0.72

0.25

Stopband Gain, LP Mode, f

= 25.6kHz

Test Frequency = 51.2kHz (2 ˇ f

)

13.6

= 4.75V, R

FIL

= 100k

Test Frequency = 102.4Hz (4 ˇ f

)

34.7

Note 1: Absolute Maximum Ratings are those value beyond which the life
of a device may be impaired.

The

denotes specifications which apply over the full operating temperature range, otherwise specifications are TA = 25

= Single 4.75V, EN pin to logic "low," Gain = 1, R

FIL

= R11 = R21 = R31 = R12 = R22 = R32, specifications apply to both the high

speed (HS) and low power (LP) modes unless otherwise noted.

LTC1563-2/LTC1563-3

LP (Pin 1): Low Power. The LTC1563-X has two operating
modes. Most applications use the part's High Speed
operating mode. Some lower frequency, lower gain appli-
cations 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.

LPA, LPB (Pins 6, 15): Lowpass Output. These pins are
the rail-to-rail outputs of an op amp. Each output is

CTIO

designed to drive a nominal net load of 5k

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 10k

. 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

(Pins 8, 16): The V

and V

pins should be

bypassed with 0.1

F 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.

LTC1563-2/LTC1563-3

INVA

LPA

AGND

LPB

INVB

0.1

LTC1563-X

ANALOG
GROUND
PLANE

DIGITAL

GROUND PLANE

(IF ANY)

1563 F01

SINGLE POINT
SYSTEM GROUND

0.1

CTIO

INVA

LPA

AGND

LPB

INVB

LTC1563-X

ANALOG
GROUND
PLANE

DIGITAL

GROUND PLANE

(IF ANY)

1563 F02

SINGLE POINT
SYSTEM GROUND

0.1

Figure 1. Dual Supply Power and Ground Connections

Figure 2. Single Supply Power and Ground Connections

BLOCK DIAGRA

SHUTDOWN

SWITCH

SHUTDOWN

SWITCH

20k

AGND

LPA

INVA

R31

R21

R11

C2A

AGND

C1A

LPB

LTC1563-X

PATENT PENDING

1563 BD

INVB

R32

R22

R12

C2B

AGND

OUT

C1B

LTC1563-2/LTC1563-3

APPLICATIO

S I

FOR

ATIO

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 f

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 and
other transfer functions are achieved. For these applica-
tions, 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 assis-
tance.

Cutoff Frequency (f

) and Gain limitations

The LTC563-X has both a maximum f

limit and a mini-

mum f

limit. The maximum f

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 f

the gain is also limited to unity.

A minimum f

is dictated by the practical limitation of

reliably obtaining large valued, precision resistors. As the
desired f

decreases, the resistor value required increases.

When f

is 2.56kHz, the resistors are 1M. Obtaining a

reliable, precise 1M resistance between two points on a
printed circuit board is somewhat difficult. For example, a
1M resistor with 20M

of stray, layout related resistance

in parallel, yields a net effective resistance of 952k and an
error of 5%. Note that the gain is also limited to unity at
the minimum f

At intermediate f

, 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 assis-
tance.

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.

Output Loading: Resistive and Capacitive

The op amps of the LTC1563-X have a rail-to-rail output
stage. To obtain maximum performance, the output load-
ing effects must be considered. Output loading issues can
be divided into resistive effects and capacitive effects.

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.

FilterCAD is trademark of Linear Technology Corporation.

LTC1563-2/LTC1563-3

APPLICATIO

S I

FOR

ATIO

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.

Layout Precautions

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 par-
allel with an on-chip capacitor, or to an AC ground, can
alter the transfer function.

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
near the cutoff frequency. Poor layout can give 0.5dB to
1dB of excess peaking.

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.

LTC1563-2/LTC1563-3

Figure 3. 4th Order Filter Connections (Power Supply, Ground,
EN and LP Connections Not Shown for Clarity). Table 1 Shows
Resistor Values

INVA

LPA

AGND

LPB

INVB

OUT

LTC1563-2

1563 F03

R31

R32

R22

R21

R11

R12

4th Order Filter Responses Using the LTC1563-2

FREQUENCY (Hz)

0.1

GAIN (dB)

1563 F03a

NORMALIZED TO f

= 1Hz

BUTTERWORTH
0.5dB RIPPLE
CHEBYSHEV

0.1dB RIPPLE
CHEBYSHEV

Figure 3a. Frequency Response

FREQUENCY (Hz)

0.1

GAIN (dB)

1563 F03b

BUTTERWORTH
0.5dB RIPPLE
CHEBYSHEV

0.1dB RIPPLE
CHEBYSHEV

NORMALIZED TO f

= 1Hz

Figure 3b. Passband Frequency Response

TIME (s)

OUTPUT VOLTAGE (V)

1.2

1.0

0.8

0.6

0.4

0.2

1.0

0.5

1.5

2.0

1563 F03C

2.5

3.0

BUTTERWORTH
0.5dB RIPPLE
CHEBYSHEV

0.1dB RIPPLE
CHEBYSHEV

NORMALIZED TO f

= 1Hz

Figure 3c. Step Response

Table 1. Resistor Values, Normalized to 256kHz Cutoff Frequency (f

), Figure 3. The Passband

Gain, of the 4th Order LTC1563-2 Lowpass Filter, Is Set to Unity. (Note 1)

0.1dB RIPPLE

0.5dB RIPPLE

BUTTERWORTH

CHEBYSHEV

LP Mode Max f

25.6kHz

15kHz

13kHz

HS Mode Max f

256kHz

135kHz

113kHz

R11 = R21 =

10k(256kHz/f

)

13.7k(256kHz/f

)

20.5k(256kHz/f

)

R31 =

10k(256kHz/f

)

10.7k(256kHz/f

)

12.4k(256kHz/f

)

R12 = R22 =

10k(256kHz/f

)

10k(256kHz/f

)

12.1k(256kHz/f

)

R32 =

10k(256kHz/f

)

6.81k(256kHz/f

)

6.98k(256kHz/f

)

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.

TYPICAL APPLICATIO S

LTC1563-2/LTC1563-3

Table 2. Resistor Values, Normalized to 256kHz Cutoff Frequency (f

), Figure 4. The Passband

Gain, of the 4th Order LTC1563-3 Lowpass Filter, Is Set to Unity. (Note 1)

TRANSITIONAL

BESSEL

GAUSSIAN TO 6dB

GAUSSIAN TO 12dB

LP Mode Max f

25.6kHz

20kHz

21kHz

HS Mode Max f

256kHz

175kHz

185kHz

R11 = R21 =

10k(256kHz/f

)

17.4k(256kHz/f

)

15k(256kHz/f

)

R31 =

10k(256kHz/f

)

13.3k(256kHz/f

)

11.8k(256kHz/f

)

R12 = R22 =

10k(256kHz/f

)

14.3k(256kHz/f

)

10.5k(256kHz/f

)

R32 =

10k(256kHz/f

)

6.04k(256kHz/f

)

6.19k(256kHz/f

)

INVA

LPA

AGND

LPB

INVB

OUT

LTC1563-3

1563 F04

R31

R32

R22

R21

R11

R12

Figure 4. 4th Order Filter Connections (Power Supply, Ground,
EN and LP Connections Not Shown for Clarity). Table 2 Shows
Resistor Values

FREQUENCY (Hz)

0.1

GAIN (dB)

1563 F04a

NORMALIZED TO f

= 1Hz

BESSEL
TRANSITIONAL
GAUSSIAN TO 12dB

TRANSITIONAL
GAUSSIAN TO 6dB

4th Order Filter Responses Using the LTC1563-3

Figure 4a. Frequency Response

Figure 4b. Step Response

Figure 4c. Step Response--Settling

TIME (s)

OUTPUT VOLTAGE (V)

1.2

1.0

0.8

0.6

0.4

0.2

1.0

0.5

1.5

2.0

1563 F04b

2.5

3.0

BESSEL
TRANSITIONAL
GAUSSIAN TO 12dB

TRANSITIONAL
GAUSSIAN TO 6dB

NORMALIZED TO f

= 1Hz

TIME (s)

OUTPUT VOLTAGE (V)

2.0

1563 F04c

0.5

1.0

1.5

1.05

1.00

0.95

BESSEL
TRANSITIONAL
GAUSSIAN TO 12dB

TRANSITIONAL
GAUSSIAN TO 6dB

NORMALIZED TO f

= 1Hz

TYPICAL APPLICATIO S

LTC1563-2/LTC1563-3

FREQUENCY (kHz)

GAIN (dB)

100

1563 TA04

INVA

LPA

AGND

LPB

INVB

OUT

ENABLE

1563 TA03

162k

93.1k

158k

267k

158k

0.1

LTC1563-2

0.1

5V, 2.3mA Supply Current, 20kHz, 4th Order,

0.5dB Ripple Chebyshev Lowpass Filter

Frequency Response

INVA

LPA

AGND

LPB

INVB

ENABLE

113k

191k

80.6k

205k

LTC1563-2

133k

113k

80.6k

INVA

LPA

AGND

LPB

INVB

OUT

3.3V

1563 TA05

73.2k

97.6k

154k

205k

154k

0.1

Single 3.3V, 2mA Supply Current, 20kHz 8th Order Butterworth Lowpass Filter

FREQUENCY (kHz)

GAIN (dB)

100

1563 TA06

Frequency Response

TYPICAL APPLICATIO S

LTC1563-2/LTC1563-3

INVA

LPA

AGND

LPB

INVB

OUT

3.3V

ENABLE

1563 TA07

10k

LTC1563-3

0.1

FREQUENCY (Hz)

10k

GAIN (dB)

100k

1563 TA08

Single 3.3V, 256kHz Bessel Lowpass Filter

Frequency Response

156323i LT/TP 0100 4K ˇ PRINTED IN USA

LINEAR TECHNOLOGY CORPORATION 2000

Linear Technology Corporation

1630 McCarthy Blvd., Milpitas, CA 95035-7417

(408) 432-1900

FAX: (408) 434-0507

www.linear-tech.com

RELATED PARTS

PART NUMBER

DESCRIPTION

COMMENTS

LTC1560-1

5-Pole Elliptic Lowpass, f

= 1MHz/0.5MHz

No External Components, SO-8

LTC1562

Universal Quad 2-Pole Active RC

10kHz < f

< 150kHz

LTC1562-2

Universal Quad 2-Pole Active RC

20kHz < f

< 300kHz

LTC1569-6

Low Power 10-Pole Delay Equalized Elliptic Lowpass

< 80kHz, One Resistor Sets f

, SO-8

LTC1569-7

10-Pole Delay Equalized Elliptic Lowpass

< 256kHz, One Resistor Sets f

, SO-8

GN Package

16-Lead Plastic SSOP (Narrow 0.150)

(LTC DWG # 05-08-1641)

PACKAGE DESCRIPTIO

GN16 (SSOP) 1098

* 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

0.016 0.050

(0.406 1.270)

0.015

0.004

(0.38

0.10)

TYP

0.007 0.0098

(0.178 0.249)

0.053 0.068

(1.351 1.727)

0.008 0.012

(0.203 0.305)

0.004 0.0098

(0.102 0.249)

0.0250

(0.635)

BSC

0.229 0.244

(5.817 6.198)

0.150 0.157**

(3.810 3.988)

16 15 14 13

0.189 0.196*

(4.801 4.978)

12 11 10 9

0.009

(0.229)

REF

TYPICAL APPLICATIO S

Part Number LTC1563-3