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PDF LTC1563I Data sheet ( Hoja de datos )
| Número de pieza | LTC1563I | |
| Descripción | Active RC/ 4th Order Lowpass Filter Family | |
| Fabricantes | Linear Technology | |
| Logotipo |  |
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FEATURES
s Extremely Easy to Use—A Single Resistor Value
Sets the Cutoff Frequency (2.56kHz < fC < 256kHz)
s Extremely Flexible—Different Resistor Values
Allow Arbitrary Transfer Functions with or without
Gain (2.56kHz < fC < 256kHz)
s LTC1563-2: Unity-Gain Butterworth Response Uses a
Single Resistor Value, Different Resistor Values
Allow Other Responses with or without Gain
s LTC1563-3: Unity-Gain Bessel Response Uses a
Single Resistor Value, Different Resistor Values
Allow Other Responses with or without Gain
s Rail-to-Rail Input and Output Voltages
s Operates from a Single 3V (2.7V Min) to ±5V Supply
s Low Noise: 36µVRMS for fC = 25.6kHz, 60µVRMS for
fC = 256kHz
s fC Accuracy < ±2% (Typ)
s DC Offset < 1mV
s Cascadable to Form 8th Order Lowpass Filters
s Low Power Mode, fC < 25.6kHz, ISUPPLY =1mA (Typ)
s High Speed Mode, fC < 256kHz, ISUPPLY = 10mA (Typ)
s Shutdown Mode, ISUPPLY = 1µA (Typ)
s Continuous Time, Active RC Filter, No Clock
U
APPLICATIONS
s Replaces Discrete RC Active Filters and Modules
s Antialiasing Filters
s Smoothing or Reconstruction Filters
s Linear Phase Filtering for Data Communication
s Phase Locked Loops
Final Electrical Specifications
LTC1563-2/LTC1563-3
Active RC, 4th Order
Lowpass Filter Family
DESCRIPTION
January 2000
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/fC); 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 (SO-8 footprint).
, LTC and LT are registered trademarks of Linear Technology Corporation.
TYPICAL APPLICATION
Single 3.3V, 2.56kHz to 256kHz Butterworth Lowpass Filter
3.3V
0.1µF
R
R
R
VIN
1µF
LTC1563-2
1
LP
V+ 16
2
SA
3
NC
4
INVA
15
LPB
14
NC
13
INVB
5
NC
6
LPA
7
AGND
12
NC
11
SB
10
NC
8 V–
9
EN
( )fC = 256kHz
10k
R
VOUT
R
R
R
1563 TA01
10
0
–10
–20
–30
–40
–50
–60
–70
–80
1k
Frequency Response
R = 10k
fC = 256kHz
R = 1M
fC = 2.56kHz
10k 100k
FREQUENCY (Hz)
1M
1563 TA02
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.
1
1 page  
LTC1563-2/LTC1563-3
PIN FUNCTIONS
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
designed to drive a nominal net load of 5kΩ 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 0.1µF 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 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.
5
5 Page 
LTC1563-2/LTC1563-3
TYPICAL APPLICATIO S
±5V, 2.3mA Supply Current, 20kHz, 4th Order,
0.5dB Ripple Chebyshev Lowpass Filter
Frequency Response
162k
267k
VIN
267k
–5V
0.1µF
LTC1563-2
1 LP
2
SA
3
NC
4
INVA
5
NC
6
LPA
7
AGND
8 V–
V+ 16
15
LPB
14
NC
13
INVB
12
NC
11
SB
10
NC
9
EN
158k
93.1k
VOUT
5V
0.1µF
158k
ENABLE
1563 TA03
10
0
–10
–20
–30
–40
–50
–60
–70
–80
–90
1
10
FREQUENCY (kHz)
100
1563 TA04
Single 3.3V, 2mA Supply Current, 20kHz 8th Order Butterworth Lowpass Filter
113k
133k
113k
VIN
ENABLE
1µF
LTC1563-2
1 LP
2 SA
3
NC
4
INVA
5
NC
6
LPA
7
AGND
8 V–
V+ 16
15
LPB
14
NC
13
INVB
12
NC
11
SB
10
NC
9
EN
0.1µF
205k
80.6k
191k
80.6k
73.2k
205k
1µF
LTC1563-2
1 LP
2 SA
3
NC
4
INVA
5
NC
6
LPA
7
AGND
8 V–
V+ 16
15
LPB
14
NC
13
INVB
12
NC
11
SB
10
NC
9
EN
3.3V
0.1µF
154k
VOUT
97.6k
154k
1563 TA05
10
0
–10
–20
–30
–40
–50
–60
–70
–80
–90
1
Frequency Response
10
FREQUENCY (kHz)
100
1563 TA06
11
11 Page | ||
| Páginas | Total 12 Páginas | |
| PDF Descargar | [ Datasheet LTC1563I.PDF ] | |
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