LTC1565-31CS8 [Linear]
650kHz Continuous Time, Linear Phase Lowpass Filter; 650kHz的连续时间，线性相位低通滤波器
| 型号： | LTC1565-31CS8 |
| 厂家： | 
Linear |
| 描述： | 650kHz Continuous Time, Linear Phase Lowpass Filter |
| 文件： | 总8页 (文件大小：140K) |
| 中文： | 中文翻译 | 下载： | 下载PDF数据表文档文件 |
Final Electrical Specifications
LTC1565-31
650kHz Continuous Time,
Linear Phase Lowpass Filter
March 2000
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FEATURES
DESCRIPTIO
The LTC®1565-31 is a 7th order, continuous time, linear
phase lowpass filter. The selectivity of the LTC1565-31,
combined with its linear phase and dynamic range, make it
suitable for filtering in data communications or data acqui-
sition systems. The filter attenuation is 37dB at 2× fCUTOFF
and at least 72dB for frequencies above 3× fCUTOFF. Unlike
comparable LC filters, the LTC1565-31 achieves this selec-
tivity with a linear phase response in the passband.
■
7th Order, 650kHz Linear Phase Filter in an SO-8
■
Differential Inputs and Outputs
■
Operates on a Single 5V or a ±5V Supply
Low Offset: 5mV Typical
75dB THD and SNR
78dB SNR
Shutdown Mode
Requires No External Components
Requires No External Clock Signal
■
■
■
■
■
■
With 5% accuracy of the cutoff frequency, the LTC1565-31
canbeusedinapplicationsrequiringpairsofmatchedfilters,
such as transceiver I and Q channels. Furthermore, the
differential inputs and outputs provide a simple interface for
these wireless systems.
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APPLICATIO S
■
CDMA Base Stations
■
Data Communications
With a single 5V supply and a 2VP-P input, the LTC1565-31
featuresanimpressivespuriousfreedynamicrangeof75dB.
Themaximumsignal-to-noiseratiois78dBanditisachieved
with a 2.5VP-P input signal.
■
Antialiasing Filters
Smoothing or Reconstruction Filters
Matched Filter Pairs
Replacement for LC Filters
■
■
■
The LTC1565-31 features a shutdown mode where power
supply current is reduced to less than 10µA.
Other cutoff frequencies and single-ended I/O can be pro-
vided upon request. Please contact LTC Marketing.
, LTC and LT are registered trademarks of Linear Technology Corporation.
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TYPICAL APPLICATIO
Frequency Response
20
0
2.0
1.8
1.6
1.4
1.2
1.0
0.8
GAIN
Single 5V Supply, Differential 650kHz Lowpass Filter
1
2
8
7
+
–
+
–
V
V
V
V
+IN
–IN
+OUT
–OUT
IN
IN
OUT
OUT
–20
–40
–60
–80
–100
GROUP DELAY
LTC1565-31
5V
5V
3
4
6
5
0.1µF
+
GND
V
0.1µF
–
V
SHDN
15645-31 TA01
4
5
6
7
10
10
10
10
FREQUENCY (Hz)
1565-31 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-
tationthattheinterconnectionofitscircuitsasdescribedhereinwillnotinfringeonexistingpatentrights.
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LTC1565-31
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ABSOLUTE MAXIMUM RATINGS
PACKAGE/ORDER INFORMATION
(Note 1)
ORDER PART
Total Supply Voltage............................................... 11V
Power Dissipation............................................. 500mW
Operating Temperature Range
LTC1565-31CS8 ..................................... 0°C to 70°C
LTC1565-31IS8 ................................. –40°C to 85°C
Storage Temperature Range ................ –65°C to 150°C
Lead Temperature (Soldering, 10 sec)................. 300°C
TOP VIEW
NUMBER
+IN
–IN
1
2
3
4
8
7
6
5
+OUT
–OUT
LTC1565-31CS8
LTC1565-31IS8
+
GND
V
–
V
SHDN
S8 PART MARKING
S8 PACKAGE
8-LEAD PLASTIC SO
156531
56531I
TJMAX = 150°C, θJA = 80°C/ W (NOTE 5)
Consult factory for Military grade parts.
ELECTRICAL CHARACTERISTICS
The ● denotes the specifications which apply over the full operating
temperature range, otherwise specifications are at TA = 25°C. VS = 5V (V+ = 5V, V– = 0V), RLOAD = 10k from each output to AC ground,
and Pin 5 open unless otherwise specified.
PARAMETER
CONDITIONS
MIN
TYP
MAX
UNITS
Operating Supply Voltage
Filter Gain
4.75
11
V
V
= 1V , f = 25kHz
●
●
●
●
●
●
●
–0.3
–0.2
–0.7
–2.2
–4
0
0
0.3
0.1
–0.1
–1.0
–2
–7
–31
dB
dB
dB
dB
dB
dB
dB
dB
IN
P-P IN
f
f
f
f
f
f
f
= 200kHz (Gain Relative to 25kHz)
= 300kHz (Gain Relative to 25kHz)
= 500kHz (Gain Relative to 25kHz)
= 650kHz (Gain Relative to 25kHz)
= 900kHz (Gain Relative to 25kHz)
= 1.3MHz (Gain Relative to 25kHz)
= 2.3MHz (Gain Relative to 25kHz)
IN
IN
IN
IN
IN
IN
IN
–0.4
–1.6
–3
–11
–36
–72
Filter Phase
V
= 1V , f = 25kHz
–13
–101
–150
113
60
36
–92
Deg
Deg
Deg
Deg
Deg
Deg
Deg
IN
P-P IN
f
f
f
f
f
f
= 200kHz
= 300kHz
= 500kHz
= 600kHz
= 650kHz
= 900kHz
IN
IN
IN
IN
IN
IN
●
●
–162
34
–138
85
Phase Linearity
Wideband Noise
THD
Ratio of 600kHz Phase/300kHz Phase
Noise BW = DC to 2 • f
●
1.97
2
2.03
115
85
µV
RMS
CUTOFF
f
= 100kHz, 1V (Note 2)
dB
IN
P-P
Filter Differential DC Swing
Maximum Difference Between Pins 7 and 8
V = 5V
V = ±5V
S
●
●
±1.4
±2.2
±1.7
±2.3
±1.9
±2.5
V
V
S
P
P
+
Filter DC Common Mode Range (Note 4)
Upper
Lower
V – 1.5
V
V
–
V + 0.8
Input Bias Current
Input Offset Current
Input Resistance
0.1
0.3
25
0.6
µA
nA
Common Mode, V = 1.5V to 3.5V
Differential
>50
>50
MΩ
MΩ
IN
Input Capacitance
2
pF
Output DC Offset (Note 3)
V = 5V
V = ±5V (Note 6)
S
±5
±5
±12
±12
mV
mV
S
2
LTC1565-31
ELECTRICAL CHARACTERISTICS
and Pin 5 open unless otherwise specified.
The ● denotes the specifications which apply over the full operating
temperature range, otherwise specifications are at TA = 25°C. VS = 5V (V+ = 5V, V– = 0V), RLOAD = 10k from each output to AC ground,
PARAMETER
CONDITIONS
V = 5V
V = ±5V
S
MIN
TYP
MAX
UNITS
Output DC Offset Drift
–400
–400
µV/°C
µV/°C
S
Ground Voltage (Pin 3) in
Single Supply Applications
V = 5V
S
●
2.49
2.51
2.52
V
SHDN Pin Logic Thresholds
V = 5V, Minimum Logical “1”
V = 5V, Maximum Logical “0”
S
4.2
3.3
V
V
S
V = ±5V, Minimum Logical “1”
V = ±5V, Maximum Logical “0”
S
2.75
2.50
V
V
S
SHDN Pin Pull-Up Current
V = 5V
V = ±5V
S
5
9
µA
µA
S
Power Supply Current
V = 5V
V = ±5V
S
●
●
24
25
31
33
mA
mA
S
Power Supply Current in Shutdown Mode
Shutdown. Includes SHDN Pull-Up Current
V = 5V
●
●
4
10
8
20
16
40
µA
µA
S
V = ±5V
S
Note 1: Absolute Maximum Ratings are those values beyond which the life
of a device may be impaired.
voltage.” The “common mode range” is the range of common mode
voltages for which the 250mV differential output has better than 65dB
P-P
2nd or 3rd harmonic distortion.
Note 2: Input and output voltages expressed as peak-to-peak numbers are
assumed to be fully differential.
Note 5: Thermal resistance varies depending upon the amount of PC board
metal attached to the device. θ is specified for a 3.8 square inch test
board covered with 2 oz copper on both sides.
Note 3: Output DC offset is measured between Pin 8 and Pin 7 with Pin 1
and Pin 2 connected to Pin 3.
JA
Note 6: Output DC offset measurements are performed by automatic test
equipment approximately 0.5 seconds after application of power.
Note 4: A 250mV , 100kHz differential signal is applied to Pins 1 and 2.
The DC voltages at Pins 1 and 2 are equal. This is the “common mode
P-P
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PIN FUNCTIONS
+IN, –IN (Pins 1, 2): Input Pins. Signals can be applied to
either or both input pins. The DC gain from differential
inputs (Pin 1 to Pin 2) to the differential outputs (Pin 8 to
Pin 7) is 1.0V/V. The input range is described in the
Applications Information section.
The impedance seen at Pin 3 is 2.5kΩ in normal mode. In
shutdown, the pin is internally biased to the same levels
as normal mode. The impedance in shutdown mode is
typically 500kΩ but varies with supply voltage and
temperature.
V–, V+ (Pins 4, 6): Power Supply Pins. For a single 5V
supply (Pin 4 grounded), a quality 0.1µF ceramic bypass
capacitor is required from the positive supply pin (Pin 6)
tothenegativesupplypin(Pin4). Thebypassshouldbeas
close as possible to the IC. For dual supply applications
(Pin 3 is grounded), bypass Pin 6 to Pin 3 and Pin 4 to Pin
3 with a quality 0.1µF ceramic capacitor.
GND (Pin 3): Ground. The ground pin is the reference
voltage for the filter and is internally biased to one-half the
total power supply voltage of the filter, maximizing the
dynamic range of the filter. For single supply operation,
the ground pin should be bypassed with a quality 0.1µF
ceramic capacitor to Pin 4. For dual supply operation,
connect Pin 3 to a high quality DC ground. A ground plane
should be used. A poor ground will increase noise and
distortion.
The maximum voltage difference between the ground pin
(Pin 3) and the positive supply pin (Pin 6) should not
exceed 5.5V.
3
LTC1565-31
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PIN FUNCTIONS
SHDN (Pin 5): Shutdown. When the Pin 5 voltage is low,
the LTC1565-31 goes into the current saving shutdown
mode. Pin 5 has a 4µA pull-up current. Leaving Pin 5 open
will place the LTC1565-31 in its normal operating mode.
–OUT, +OUT(Pins7, 8):OutputPins. Pins7and8arethe
filter differential output. Each pin can drive 1kΩ or 300pF
loads. The common mode voltage at the output pins is the
same as the voltage at Pin 3.
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BLOCK DIAGRA
+IN
1
+
–
+OUT
8
7
R
R
OUTPUT
BUFFER
7th ORDER
LINEAR
+
–
PHASE
FILTER
NETWORK
OUTPUT
BUFFER
–
+
+
–OUT
INPUT BUFFERS
WITH COMMON MODE
TRANSLATION CIRCUIT
–IN
2
3
4
V
SHUTDOWN
SWITCH
~1M
5k
+
GND
6
V
5k
SHUTDOWN
SWITCH
~1M
+
V
–
V
4µA
–
V
SHUTDOWN
5
SHDN
1565-31 BD
4
LTC1565-31
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APPLICATIONS INFORMATION
Interfacing to the LTC1565-31
Input Common Mode and Differential Voltage Range
The difference between the voltages at Pin 1 and Pin 2 is
the“differentialinputvoltage.”Theaverageofthevoltages
at Pin 1 and Pin 2 is the “common mode input voltage.”
The difference between the voltages at Pin 7 and Pin 8 is
the “differential output voltage.” The average of the volt-
ages at Pin 7 and Pin 8 is the “common mode output
voltage.” The input and output common mode voltages
are independent. The input common mode voltage is set
by the signal source, if DC coupled, or by the biasing
network if AC coupled (Figures 1 and 2). The output
common mode voltage is equal to the voltage of Pin 3, the
GND pin. The GND pin is biased to one-half of the supply
voltage by an internal resistive divider (see Block Dia-
gram). To alter the common mode output voltage, Pin 3
can be driven with an external voltage source or resistor
network. If external resistors are used, it is important to
note that the internal 5k resistors can vary ±20% (their
ratioonlyvaries±2%). TheoutputcanalsobeACcoupled.
The range of voltage each input can support while operat-
ing in its linear region is typically 0.8V to 3.5V for a single
5V supply and –4.2V to 3.2V for a ±5V supply. Therefore,
the filter can accept a variety of common mode input
voltages. Figures 3 and 4 show the THD of the filter versus
commonmodeinputvoltagewitha2VP-P differentialinput
signal.
–30
–40
–50
–60
–70
V
V
IN
= 2V
P-P
–80
–90
IN
S
= ±5V
f
= 100kHz
–5 –4 –3 –2 –1
0
1
2
3
4
5
INPUT COMMON MODE VOLTAGE (V)
1
2
8
7
+
–
V
V
+IN
–IN
+OUT
–OUT
OUT
OUT
1565-31 F03
Figure 3. THD vs Common Mode Input Voltage
+
–
+
–
+
V
V
IN
IN
5V
–
LTC1565-31
3
4
6
5
–30
+
GND
V
0.1µF
0.1µF
–
V
SHDN
–40
–50
15645-31 F01
DC COUPLED INPUT
+
–
V
+ V
IN
V
IN
V
V
(COMMON MODE) =
IN
2
+
–
+
+ V
2
V
OUT
OUT
–60
(COMMON MODE) =
=
OUT
2
Figure 1
–70
–80
V
V
IN
= 2V
P-P
IN
S
= ±5V
f
= 100kHz
0.1µF
0.5
1.0
2.0
2.5
3.0
3.5
1.5
1
2
8
7
+
–
V
V
+IN
–IN
+OUT
–OUT
OUT
INPUT COMMON MODE VOLTAGE (V)
1565-31 F04
OUT
+
–
+
+
–
V
IN
V
IN
0.1µF
100k
100k
5V
–
LTC1565-31
Figure 4. THD vs Common Mode Input Voltage
3
4
6
5
+
GND
V
1µF
0.1µF
–
Figure 5 shows the THD and S/N ratio versus differential
input voltage level for both a single 5V supply and a ±5V
supply. The common mode voltage of the input signal is
one-half the total power supply voltage of the filter. The
spurious free dynamic range, where the THD and S/N ratio
are equal, is 75dB to 77dB when the differential input
voltage level is 2VP-P; that is, for a single 5V supply, the
V
SHDN
15645-31 F02
AC COUPLED INPUT
(COMMON MODE) = V
V
IN
(COMMON MODE)
OUT
+
V
=
2
Figure 2
5
LTC1565-31
APPLICATIONS INFORMATION
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–30
Output Common Mode and Differential Voltage Range
THD: V = 5V
S
THD: V = ±5V
S
–40
–50
–60
–70
–80
–90
SNR
Theoutputisafullydifferentialsignalwithacommonmode
level equal to the voltage at Pin 3. The specifications in the
ElectricalCharacteristicstableassumetheinputsaredriven
differentially and the output is observed differentially.
However, Pin 8 can be used as a single-ended output by
simply floating Pin 7. Pin 7 can be used as an inverting
single-ended output by floating Pin 8. Using Pins 7 or 8 as
single-ended outputs will decrease the performance.
f
= 100kHz
IN
0.5
1.5
2.0
2.5
3.0
3.5
1.0
The common mode output voltage can be adjusted by
overdriving the voltage present on Pin 3. The best perfor-
mance is achieved using a common mode output voltage
that is equal to mid supply (the default Pin 3 voltage). Fig-
ures7and8illustratetheTHDversusoutputcommonmode
voltagefora2VP-P differentialinputvoltageandacommon
mode input voltage that is 0.5V below mid supply.
DIFFERENTIAL INPUT (
)
P-P
1565-31 F05
Figure 5. Dynamic Range Diff-In, Diff-Out
input voltages are Pin 1 = 2.5V DC ±0.5V and Pin 2 = 2.5V
DC ±0.5V. Also note Figure 5 shows a 78dB SNR ratio for
higher THD levels.
0
V
V
V
= 2V 100kHz
P-P
IN
S
As seen in Figures 3 and 4, the spurious free dynamic
rangecanbeoptimizedbysettingtheinputcommonmode
voltage slightly below one-half of the power supply volt-
age, i.e., 2V for a single 5V supply and –0.5V to –1V for a
±5V supply. Figure 6 shows the THD and SNR ratio versus
differential input voltage level for both a single 5V supply
and a ±5V supply when the common mode input voltage
is 2V and –0.5V respectively.
= 5V
–10
–20
–30
= 2V
IN(CM)
–40
–50
–60
–70
–80
For best performance, the inputs should be driven differ-
entially. For single-ended signals, connect the unused
input to Pin 3 or a common mode reference.
2.0
2.5
3.5
1.5
4.0
3.0
COMMON MODE OUTPUT VOLTAGE (V)
1565-31 F07
Figure 7. THD vs Common Mode Output Voltage
–40
THD: V = 5V
S
THD: V = ±5V
S
0
SNR
= 100kHz
V
V
V
= 2V 100kHz
P-P
IN
S
–50
–60
–70
f
= ±5V
IN
–10
–20
–30
–40
–50
–60
–70
–80
–90
= –0.5V
IN(CM)
–80
–90
0.5
1.5
2.0
2.5
3.0
3.5
1.0
DIFFERENTIAL INPUT VOLTAGE (V
)
P-P
–4
–2
0
2
4
1565-31 F06
COMMON MODE OUTPUT VOLTAGE (V)
1565-31 F08
Figure 6. THD vs VIN for a Common Mode
Input Voltage 0.5V Below Mid Supply
Figure 8. THD vs Common Mode Output Voltage
6
LTC1565-31
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APPLICATIONS INFORMATION
Table 1. Wideband Noise vs Bandwidth, Single 5V Supply
BANDWIDTH TOTAL INTEGRATED NOISE
DC to f
Output Drive
Pin 7 and Pin 8 can drive a 1kΩ or 300pF load connected
to AC ground with a ±0.5V signal (corresponding to a
2VP-P differential signal). For differential loads (loads
connected from Pin 7 to Pin 8) the outputs can produce
a 2VP-P differential signal across 2kΩ or 150pF. For
smaller signal amplitudes the outputs can drive corre-
spondingly larger loads.
110µV
115µV
CUTOFF
RMS
RMS
DC to 2 • f
CUTOFF
Table 2. Wideband Noise vs Supply Voltage, fCUTOFF = 650kHz
TOTAL INTEGRATED NOISE
POWER SUPPLY
DC TO 2 • f
CUTOFF
5V
115µV
117µV
RMS
RMS
±5V
Noise
The wideband noise of the filter is the RMS value of the
device’s output noise spectral density. The wideband
noise data is used to determine the operating signal-to-
noise at a given distortion level. Most of the noise is
concentratedinthefilterpassbandandcannotberemoved
withpostfiltering(Table1). Table2liststhetypicalchange
in wideband noise with supply voltage.
DC Offset
The output DC offset of the LTC1565-31 is trimmed to less
than ±5mV. The trimming is done with VS = ±2.5V. The
output DC offset will typically change by ±1mV when the
power supply varies from 5V to ±5V.
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PACKAGE DESCRIPTION
Dimensions in inches (millimeters) unless otherwise noted.
S8 Package
8-Lead Plastic Small Outline (Narrow 0.150)
(LTC DWG # 05-08-1610)
0.189 – 0.197*
(4.801 – 5.004)
7
5
8
6
0.150 – 0.157**
(3.810 – 3.988)
0.228 – 0.244
(5.791 – 6.197)
1
3
4
2
0.010 – 0.020
(0.254 – 0.508)
× 45°
0.053 – 0.069
(1.346 – 1.752)
0.004 – 0.010
(0.101 – 0.254)
0.008 – 0.010
(0.203 – 0.254)
0°– 8° TYP
0.016 – 0.050
(0.406 – 1.270)
0.050
(1.270)
BSC
0.014 – 0.019
(0.355 – 0.483)
TYP
*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
SO8 1298
7
LTC1565-31
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TYPICAL APPLICATIO
Narrowband Cellular Base Station Receiver
LTC1565-31
LPF
ADC
ADC
0°
I
RF/IF
SECTION
90°
DSP
LO
Q
90°
LTC1565-31
LPF
1565-31 TA03
RELATED PARTS
PART NUMBER
LTC1560-1
DESCRIPTION
COMMENTS
1MHz/500kHz Continuous Time, Low Noise, Lowpass Elliptic Filter
Universal 8th Order Active RC Filters
f
= 500kHz or 1MHz
CUTOFF
LTC1562/LTC1562-2
f
f
= 150kHz (LTC1562),
= 300kHz (LTC1562-2)
CUTOFF(MAX)
CUTOFF(MAX)
LTC1563-2/LTC1563-3 4th Order Active RC Lowpass Filters
f
= 256kHz
CUTOFF(MAX)
LTC1569-6/LTC1569-7 Self Clocked, 10th Order Linear Phase Lowpass Filters
f
f
/f
= 64/1, f
= 32/1, f
= 75kHz (LTC1569-6)
= 300kHz (LTC1569-7)
CLK CUTOFF
CUTOFF(MAX)
CUTOFF(MAX)
/f
CLK CUTOFF
156531i LT/TP 0300 4K • PRINTED IN USA
LINEAR TECHNOLOGY CORPORATION 2000
LinearTechnology Corporation
1630 McCarthy Blvd., Milpitas, CA 95035-7417
8
●
●
(408)432-1900 FAX:(408)434-0507 www.linear-tech.com
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