LTC1064-1
Low Noise, 8th Order, Clock
Sweepable Elliptic Lowpass Filter
FEATURES
■
■
■
■
■
■
■
■
DESCRIPTIO
8th Order Filter in a 14-Pin Package
No External Components
100:1 Clock to Center Ratio
150µV
RMS
Total Wideband Noise
0.03% THD or Better
50kHz Maximum Corner Frequency
Operates from
±2.37V
to
±8V
Power Supplies
Passband Ripple Guaranteed Over Full Military
Temperature Range
The LTC
®
1064-1 is an 8th order, clock sweepable elliptic
(Cauer) lowpass switched capacitor filter. The passband
ripple is typically
±0.15dB,
and the stopband attenuation
at 1.5 times the cutoff frequency is 68dB or more.
An external TTL or CMOS clock programs the value of the
filter’s cutoff frequency. The clock to cutoff frequency ratio
is 100:1.
No external components are needed for cutoff frequencies
up to 20kHz. For cutoff frequencies over 20kHz two low
value capacitors are required to maintain passband flatness.
The LTC1064-1 features low wideband noise and low
harmonic distortion even for input voltages up to 3V
RMS
.
In fact the LTC1064-1 overall performance completes with
equivalent multiple op amp RC active realizations.
The LTC1064-1 is available in a 14-pin DIP or 16-pin
surface mounted SW package.
The LTC1064-1 is pin compatible with the LTC1064-2.
, LTC and LT are registered trademarks of Linear Technology Corporation.
APPLICATIO S
■
■
Antialiasing Filters
Telecom PCM Filters
TYPICAL APPLICATIO
1
V
IN
2
3
8V
0.1µF
14
13
8th Order Clock Sweepable Lowpass
Elliptic Antialiasing Filter
15
0
–15
INV C
V
IN
R(h, I)
COMP2*
V
OUT
/V
IN
(dB)
AGND
4
+
LTC1064-1
11
CLOCK
f
CLK
V
(TTL,
≤5MHz)
5
10
NC
AGND
6
7
COMP1*
INV A
V
OUT
NC
9
8
V
OUT
12
V
–
–8V
0.1µF
–30
–45
–60
–75
–90
–105
0
5
10
15 20 25 30
FREQUENCY (kHz)
35
40
1064 TA01
NOTE: THE POWER SUPPLIES SHOULD BE BYPASSED BY A 0.1µF
CAPACITOR CLOSE TO THE PACKAGE.
FOR SERVO OFFSET NULLING APPLICATIONS, PIN 1 IS THE 2ND
STAGE SUMMING JUNCTION.
*FOR CUTOFF FREQUENCY ABOVE 20kHz, USE COMPENSATION
CAPACITORS (5pF TO 56pF) BETWEEN PIN 13 AND PIN 1
AND PIN 6 AND PIN 7.
8th ORDER CLOCK SWEEPABLE LOWPASS ELLIPTIC ANTIALIASING
FILTER MAINTAINS, FOR 0.1Hz
≤
f
CUTOFF
≤
10kHz, A
±0.15dB
PASSBAND
RIPPLE AND 72dB STOPBAND ATTENUATION AT 1.5
×
f
CUTOFF
.
TOTAL WIDEBAND NOISE = 150µV
RMS
, THD = 0.03% FOR V
IN
= 1V
RMS
10641fa
U
Frequency Response
1064 TA02
U
U
1
LTC1064-1
ABSOLUTE
AXI U RATI GS
Total Supply Voltage (V
+
to V
–
) ............................ 16.5V
Power Dissipation .............................................. 400mW
Storage Temperature Range ................. – 65°C to 150°C
Lead Temperature (Soldering, 10 sec).................. 300°C
PACKAGE/ORDER I FOR ATIO
TOP VIEW
INV C
V
IN
AGND
V
+
AGND
COMP1
INV A
1
2
3
4
5
6
7
14 R(h, l)
13 COMP2
12
V
–
ORDER PART
NUMBER
INV C 1
11 f
CLK
10 NC
9
8
V
OUT
NC
LTC1064-1CN
LTC1064-1ACN
N PACKAGE
14-LEAD PDIP
T
JMAX
= 110°C,
θ
JA
= 70°C/W
J PACKAGE
14-LEAD CERDIP
OBSOLETE PACKAGE
Consider the N14 Package for Alternate Source
LTC1064-1MJ
LTC1064-1CJ
Consult LTC Marketing for parts specified with wider operating temperature ranges.
ELECTRICAL CHARACTERISTICS
PARAMETER
Passband Gain, LTC1064-1, 1A
Gain TempCo
Passband Edge Frequency, f
C
Gain at f
C
LTC1064-1
LTC1064-1A
–3dB Frequency
Passband Ripple (Note 1)
LTC1064-1
LTC1064-1A
Ripple TempCo
Stopband Attenuation
LTC1064-1
LTC1064-1A
Stopband Attenuation
LTC1064-1
LTC1064-1A
CONDITIONS
The
●
denotes the specifications which apply over the full operating
temperature range, otherwise specifications are at T
A
= 25°C. V
S
=
±7.5V,
f
CLK
= 1MHz, R1 = 10k, C1 = 10pF, TTL or CMOS clock input
level unless otherwise specified.
MIN
●
Referenced to 0dB, 1Hz to 0.1f
C
Referenced to Passband Gain
●
●
0.1f
C
to 0.85f
C
Referenced to Passband Gain,
Measured at 6.25kHz and 8.5kHz
At 1.5f
C
Referenced to 0dB
●
●
At 2f
C
Referenced to 0dB
●
●
2
U
U
W
W W
U
W
(Note 1)
Operating Temperature Range
LTC1064-1M
(OBSOLETE)
............... – 55°C to 125°C
LTC1064-1C/AC .................................. – 40°C to 85°C
TOP VIEW
16 R(h, l)
15 COMP2
14 V
–
13 NC
12 f
CLK
11 NC
10 NC
9
V
OUT
ORDER PART
NUMBER
LTC1064-1CSW
V
IN
2
AGND 3
V
+
4
AGND 5
NC 6
COMP1 7
INV A 8
SW PACKAGE
16-LEAD PLASTIC (WIDE) SO
T
JMAX
= 150°C,
θ
JA
= 90°C/W
TYP
±
0.1
0.0002
10
±
1%
MAX
±
0.35
UNITS
dB
dB/°C
kHz
–1.25
– 0.75
10.7
0.85
0.65
dB
dB
kHz
●
●
±
0.15
±
0.1
0.0004
66
68
67
68
72
72
72
72
±
0.32
±
0.19
dB
dB
dB/°C
dB
dB
dB
dB
10641fa
LTC1064-1
The
●
denotes the specifications which apply over the full operating
temperature range, otherwise specifications are at T
A
= 25°C. V
S
=
±7.5V,
f
CLK
= 1MHz, R1 = 10k, C1 = 10pF, TTL or CMOS clock input
level unless otherwise specified.
PARAMETER
Input Frequency Range
Output Voltage Swing and
Operating Input Voltage Range
Total Harmonic Distortion
Wideband Noise
Output DC Offset
LTC1064-1
LTC1064-1A
Output DC Offset TempCo
Input Impedance
Output Impedance
Output Short-Circuit Current
Clock Feedthrough
Maximum Clock Frequency
Power Supply Current
50% Duty Cycle, V
S
=
±7.5V
V
S
=
±2.37V
V
S
=
±5V
●
●
ELECTRICAL CHARACTERISTICS
CONDITIONS
V
S
=
±2.37V
V
S
=
±5V
V
S
=
±7.5V
MIN
0
●
●
●
TYP
MAX
f
CLK
/2
UNITS
kHz
V
V
V
±1
±3
±5
0.015
0.03
150
165
50
50
–100
10
20
2
3/1
200
5
10
12
16
22
23
26
28
32
±8
175
125
V
S
=
±5V,
Input = 1V
RMS
at 1kHz
V
S
=
±7.5V,
Input = 3V
RMS
at 1kHz
V
S
=
±5V,
Input = GND 1Hz to 999kHz
V
S
=
±7.5V,
Input = GND 1Hz to 999kHz
V
S
=
±7.5V,
Pin 2 Grounded
%
%
µV
RMS
µV
RMS
mV
mV
µV/°C
kΩ
Ω
mA
µV
RMS
MHz
mA
mA
mA
mA
mA
V
V
S
=
±5V
f
OUT
= 10kHz
Source/Sink
V
S
=
±7.5V,
f
CLK
= 1MHz
●
Power Supply Voltage Range
Note 1:
Absolute Maximum Ratings are those values beyond which the life
of a device may be impaired.
●
±2.37
Note 2:
For tighter specifications please contact LTC Marketing.
TYPICAL PERFOR A CE CHARACTERISTICS
Gain vs Frequency
15
0
–15
GAIN (dB)
–30
–45
–60
–75
–90
V
S
=
±5V
T
A
= 25°C
f
CLK
= 1MHz
f
C
= 10kHz
±
0.1dB
f
–3dB
= 10.7kHz
1
10
FREQUENCY (kHz)
100
1064 G01
–180
–225
–270
–315
–360
–405
–450
0
1
2
3
4 5 6 7 8
FREQUENCY (kHz)
9 10 11
1064 G02
GROUP DELAY (µs)
PHASE (DEG)
–105
U W
Phase vs Frequency
0
–45
–90
–135
V
S
=
±5V
T
A
= 25°C
f
CLK
= 1MHz
f
C
= 10kHz
500
Group Delay
V
S
=
±5V
450 T
A
= 25°C
400 f
CLK
= 1MHz
f
C
= 10kHz
350
300
250
200
150
100
50
0
0
1
2
3
5 6 7 8 9 10 11 12
FREQUENCY (kHz)
1064 G03
4
10641fa
3
LTC1064-1
TYPICAL PERFOR A CE CHARACTERISTICS
Gain vs Frequency
15
0
–15
f
CLK
= 2MHz, f
C
= 20kHz
COMP1 NOT USED,
COMP2 = 20pF
f
CLK
= 3MHz, f
C
= 30kHz
COMP1 = 24pF
COMP2 = 36pF
f
CLK
= 4MHz, f
C
= 40kHz
COMP1 = 36pF
COMP2 = 47pF
V
S
=
±5V
T
A
= 25°C
1
10
FREQUENCY (kHz)
100
1064 G04
GAIN (dB)
GAIN (dB)
–45
–60
–75
–90
–45
–60
–75
–90
f
CLK
= 4MHz, f
C
= 40kHz
COMP1 = 20pF
COMP2 = 30pF
f
CLK
= 5MHz, f
C
= 50kHz
COMP1 = 30pF
COMP2 = 47pF
V
S
=
±7.5V
T
A
= 25°C
1
10
FREQUENCY (kHz)
100
1064 G05
GAIN (dB)
–30
–105
Typical Wideband Noise
(151µV
RMS
) V
S
=
±
5V, T
A
= 25°C
f
CLK
= 1MHz, f
C
= 10kHz Input
Grounded
POWER SUPPLY CURRENT (mA)
PI FU CTIO S
(Pin Numbers Refer to the 14-Pin Package)
COMP1, INV A, COMP2, INV C (Pins 1,6,7, and 13):
For
filter cutoff frequencies higher than 20kHz, in order to
minimize the passband ripple, compensation capacitors
should be added between Pin 6 and Pin 7 (COMP1) and
Pin 1 and Pin 13 (COMP2). For COMP1 (COMP2), add 1pF
(1.5pF) mica capacitor for each kHz increase in cutoff
frequency above 20kHz. For more detail refer to Gain vs
Frequency graphs.
V
IN
, V
OUT
(Pins 2, 9):
The input Pin 2 is connected to an
18k resistor tied to the inverting input of an op amp. Pin 2
4
U W
Gain vs Frequency
15
0
–15
–30
f
CLK
= 3MHz, f
C
= 30kHz
COMP1 = 10pF
COMP2 = 15pF
5
0
–5
–10
–15
–20
Gain vs Frequency
25°C GAIN PEAK =
0.4dB AT 30kHz
–105
V
S
=
±7.5V
f
CLK
= 5MHz 125°C GAIN PEAK =
f = 50kHz
1dB AT 35kHz
–30
C
COMP1 = 33pF
COMP2 = 56pF
–35
1
10
FREQUENCY (kHz)
–25
100
1064 G06
Total Harmonic Distortion
(0.025%) V
S
=
±
7.5V, T
A
= 25°C
f
CLK
= 1MHz, f
C
= 10kHz
Input = 1kHz at 3V
RMS
48
44
40
36
32
28
24
20
16
12
8
4
0
Power Supply Current vs Power
Supply Voltage
f
CLK
= 1MHz
T
A
= –55°C
T
A
= 25°C
T
A
= 125°C
0 2
4 6 8 10 12 14 16 18 20 22 24
TOTAL POWER SUPPLY VOLTAGE (V)
1064 G09
U
U
U
is protected against static discharge. The device’s output,
Pin 9, is the output of an op amp which can typically source/
sink 3mA/1mA. Although the internal op amps are unity
gain stable, driving long coax cables is not recommended.
When testing the device for noise and distortion, the
output, Pin 9, should be buffered (Figure 4).
The op amp
power supply wire (or trace) should be connected
directly to the power source.
AGND (Pins 3, 5):
For dual supply operation these pins
should be connected to a ground plane. For single supply
10641fa
LTC1064-1
PI FU CTIO S
operation both pins should be tied to one half supply
(Figure 2). Also Pin 8 and Pin 10, although they are not
internally connected should be tied to analog ground or
system ground. This improves the clock feedthrough
performance.
V
+
, V
–
(Pins 4, 12):
The V
+
and V
–
pins should be
bypassed with a 0.1µF capacitor to an adequate analog
ground. Low noise, nonswitching power supplies are
recommended.
To avoid latchup when the power supplies
exhibit high turn-on transients, a 1N5817 Schottky diode
should be added from the V
+
and V
–
pins to ground
(Figure 1).
INV A, R(h, I) (Pins 7, 14):
A very short connection
between Pin 14 and Pin 7 is recommended. This connec-
tion should be preferably done under the IC package. In a
TYPICAL APPLICATIO S
1
V
IN
2
3
V
+
1N5817
0.1µF
INV C
V
IN
R(h, I)
COMP2*
14
13
V
–
1N5817
0.1µF
12
V
–
AGND
4
+
LTC1064-1
11
f
CLK
V
5
6
7
AGND
COMP1*
INV A
NC
V
OUT
NC
10
9
8
Figure 1. Using Schottky Diodes to Protect
the IC from Power Supply Spikes
1
V
IN
2
3
V
+
5k
INV C
V
IN
R(h, I)
COMP2*
14
13
12
V
–
AGND
LTC1064-1
4
+
11
f
CLK
V
5
6
AGND
COMP1*
INV A
NC
V
OUT
NC
10
9
8
0.1µF
5k
7
Figure 3. Level Shifting the Input T
2
L Clock
for Single Supply Operation, V+ >6V.
U
U
U
U
(Pin Numbers Refer to the 14-Pin Package)
breadboard, use a one inch, or less, shielded coaxial cable;
the shield should be grounded. In a PC board, use a one
inch trace or less; surround the trace by a ground plane.
NC (Pins 8, 10):
The “no connection” pins preferably
should be grounded.
f
CLK
(Pin 11):
For
±5V
supplies the logic threshold level is
1.4V. For
±8V
and 0V to 5V supplies the logic threshold
levels are 2.2V and 3V respectively. The logic threshold
levels vary
±100mV
over the full military temperature
range. The recommended duty cycle of the input clock is
50% although for clock frequencies below 500kHz the
clock “on” time can be as low as 200ns. The maximum
clock frequency for
±5V
supplies is 4MHz. For
±7V
sup-
plies and above, the maximum clock frequency is 5MHz.
Do not allow the clock levels to exceed the power supplies.
For clock level shifting (see Figure 3).
1
V
IN
2
3
V
+
= 15V
0.1µF
5k
V
OUT
INV C
V
IN
R(h, I)
COMP2*
14
13
12
V
–
AGND
4
+
LTC1064-1
11
f
CLK
V
5
6
V
+
/2
0.1µF
5k
7
AGND
COMP1*
INV A
NC
V
OUT
NC
10
9
8
0V TO 10V
V
OUT
1064 F01
1064 F02
Figure 2. Single Supply Operation. If Fast Power Up
or Down Transients are Expected, Use a 1N5817
Schottky Diode Between Pin 4 and Pin 5.
1
V
IN
2
3
R(h, I) 14
COMP2*
13
POWER SOURCE
V
+
V
–
INV C
V
IN
V
+
2.2k
T
2
L
LEVEL
5k 1µF
V
OUT
12
V
–
AGND
LTC1064-1
4
+
11
f
CLK
V
0.1µF
5
6
AGND
COMP1*
NC
V
OUT
NC
10
9
8
10k
0.1µF
10k
0.1µF
–
V
OUT
7 INV A
+
1064 F03
RECOMMENDED OP AMPS:
LT1022, LT318, LT1056
1064 F04
0.1µF
Figure 4. Buffering the Filter Output. The Buffer Op Amp
Should Not Share the LTC1064-1 Power Lines.
10641fa
5
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