LTC1069-7
Linear Phase
8th Order Lowpass Filter
FEATURES
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8th Order, Linear Phase Filter in SO-8 Package
Raised Cosine Amplitude Response
– 43dB Attenuation at 2× f
CUTOFF
Wideband Noise: 140μV
RMS
Operates from Single 5V Supply to
±5V Power Supplies
Clock-Tunable to 200kHz with ±5V Supplies
Clock-Tunable to 120kHz with Single 5V Supply
cutoff frequency of the LTC1069-7 is set by an external
clock and is equal to the clock frequency divided by 25.
The ratio of the internal sampling frequency to the cutoff
frequency is 50:1 that is, the input signal is sampled
twice per clock cycle to lower the risk of aliasing. The
LTC1069-7 can be operated from a single 5V supply up
to dual ±5V supplies.
The gain and phase response of the LTC1069-7 can be
used in digital communication systems where pulse
shaping and channel bandwidth limiting must be carried
out. Any system that requires an analog filter with linear
phase and sharper roll off than conventional Bessel filters
can use the LTC1069-7.
The LTC1069-7 has a wide dynamic range. With ±5V
supplies and an input range of 0.1V
RMS
to 2V
RMS
, the
signal-to-(noise + THD) ratio is ≥ 60dB. The wideband noise
of the LTC1069-7 is 140μV
RMS
.
Unlike other LTC1069-X filters,
the typical passband gain of the LTC1069-7 is equal to –1V/V.
The LTC1069-7 is available in an SO-8 package.
Other filter responses with lower power/speed specifications
can be obtained. Please contact LTC Marketing.
L,
LT, LTC and LTM are registered trademarks of Linear Technology Corporation.
APPLICATIONS
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Digital Communication Filter
Antialiasing Filter with Linear Phase
Smoothing Filters
DESCRIPTION
The LTC
®
1069-7 is a monolithic, clock-tunable, linear
phase, 8th order lowpass filter. The amplitude response
of the filter approximates a raised cosine filter with an
alpha of one. The gain at the cutoff frequency is – 3dB and
the attenuation at twice the cutoff frequency is 43dB. The
TYPICAL APPLICATION
Frequency Response
Single 5V Supply, Linear Phase 100kHz Lowpass Filter
AGND
5V
0.1μF
NC
V
IN
V
IN
LTC1069-7
NC
CLK
f
CLK
= 2.5MHz
1069-7 TA01
10
0
V
OUT
V
–
V
OUT
GAIN (dB)
–10
–20
–30
–40
–50
–60
–70
10
100
FREQUENCY (kHz)
1000
1069-7 TA02
0.47μF
V
+
10697fa
1
LTC1069-7
ABSOLUTE MAXIMUM RATINGS
Total Supply Voltage (V
+
to V
–
) ............................... 12V
Power Dissipation .............................................. 400mW
Operating Temperature Range
LTC1069-7C ............................................ 0°C to 70°C
LTC1069-7I ......................................... – 40°C to 85°C
Storage Temperature..............................–65°C to 150°C
Lead Temperature (Soldering, 10 sec) .................. 300°C
PIN CONFIGURATION
TOP VIEW
AGND 1
V
+
2
NC 3
V
IN
4
8
7
6
5
V
OUT
V
–
NC
CLK
S8 PACKAGE
8-LEAD PLASTIC SO
T
JMAX
= 125°C,
θ
JA
= 130°C/W
ORDER INFORMATION
LEAD FREE FINISH
LTC1069-7CS8#PBF
LTC1069-7IS8#PBF
TAPE AND REEL
LTC1069-7CS8#TRPBF
LTC1069-7IS8#TRPBF
PART MARKING
10697
10697I
PACKAGE DESCRIPTION
8-Lead Plastic SO
8-Lead Plastic SO
TEMPERATURE RANGE
0°C to 70°C
–40°C to 85°C
Consult LTC Marketing for parts specified with wider operating temperature ranges.
Consult LTC Marketing for information on non-standard lead based finish parts.
For more information on lead free part marking, go to:
http://www.linear.com/leadfree/
For more information on tape and reel specifications, go to:
http://www.linear.com/tapeandreel/
The
l
denotes specifications which apply over the full operating
temperature range. f
CUTOFF
is the filter’s cutoff frequency and is equal to f
CLK
/25. The f
CLK
signal level is TTL or CMOS (max clock rise
or fall time ≤ 1μs), R
L
= 10k, T
A
= 25°C, unless otherwise specified. All AC gains are measured relative to the passband gain.
SYMBOL
Passband Gain (f
IN
≤ 0.2f
CUTOFF
)
CONDITIONS
V
S
= ± 5V, f
CLK
= 2.5MHz
f
TEST
= 1kHz, V
IN
= 1V
RMS
V
S
= 4.75V, f
CLK
= 500kHz
f
TEST
= 1kHz, V
IN
= 0.5V
RMS
Gain at 0.25f
CUTOFF
V
S
= ± 5V, f
CLK
= 2.5MHz
f
TEST
= 25kHz, V
IN
= 1V
RMS
V
S
= 4.75V, f
CLK
= 500kHz
f
TEST
= 5kHz, V
IN
= 0.5V
RMS
Gain at 0.50f
CUTOFF
V
S
= ± 5V, f
CLK
= 2.5MHz
f
TEST
= 50kHz, V
IN
= 1V
RMS
V
S
= 4.75V, f
CLK
= 500kHz
f
TEST
= 10kHz, V
IN
= 0.5V
RMS
Gain at 0.75f
CUTOFF
V
S
= ± 5V, f
CLK
= 2.5MHz
f
TEST
= 75kHz, V
IN
= 1V
RMS
V
S
= 4.75V, f
CLK
= 500kHz
f
TEST
= 15kHz, V
IN
= 0.5V
RMS
Gain at f
CUTOFF
V
S
= ± 5V, f
CLK
= 2.5MHz
f
TEST
= 100kHz, V
IN
= 1V
RMS
V
S
= 4.75V, f
CLK
= 500kHz
f
TEST
= 20kHz, V
IN
= 0.5V
RMS
l
l
l
l
l
l
l
l
l
l
ELECTRICAL CHARACTERISTICS
MIN
TYP
–0.10
–0.10
–0.30
MAX
±0.75
±0.90
±0.75
±0.90
–0.1
UNITS
dB
dB
dB
dB
dB
dB
dB
dB
dB
dB
dB
dB
dB
dB
dB
dB
dB
dB
dB
dB
10697fa
–0.55
–0.05
–0.30
–1.0
–1.40
–0.30
–0.60
–1.65
–2.1
–0.75
–1.15
–3.5
–4.0
–2.9
–3.3
0.15
–0.35
0
–0.80
–0.25
–2.7
–2.4
2
LTC1069-7
The
l
denotes specifications which apply over the full operating
temperature range. f
CUTOFF
is the filter’s cutoff frequency and is equal to f
CLK
/25. The f
CLK
signal level is TTL or CMOS (max clock rise
or fall time ≤ 1μs), R
L
= 10k, T
A
= 25°C, unless otherwise specified. All AC gains are measured relative to the passband gain.
SYMBOL
Gain at 1.5f
CUTOFF
CONDITIONS
V
S
= ± 5V, f
CLK
= 2.5MHz
f
TEST
= 150kHz, V
IN
= 1V
RMS
V
S
= 4.75V, f
CLK
= 500kHz
f
TEST
= 30kHz, V
IN
= 0.5V
RMS
Gain at 2.0f
CUTOFF
V
S
= ± 5V, f
CLK
= 2.5MHz
f
TEST
= 200kHz, V
IN
= 1V
RMS
V
S
= 4.75V, f
CLK
= 500kHz
f
TEST
= 40kHz, V
IN
= 0.5V
RMS
Gain at 5.0f
CUTOFF
Gain at f
CUTOFF
(160kHz)
Phase at 0.5f
CUTOFF
Phase at f
CUTOFF
Passband Phase Deviation from
Linear Phase (Note 1)
Output DC Offset (Input at GND)
Output Voltage Swing
Power Supply Current
V
S
= 4.75V, f
CLK
= 500kHz
f
TEST
= 100kHz, V
IN
= 0.5V
RMS
V
S
= ±5V, f
CLK
= 4MHz
f
TEST
= 160kHz, V
IN
= 1V
RMS
V
S
= ±5V, f
CLK
= 2.5MHz
f
TEST
= 50kHz
V
S
= ±5V, f
CLK
= 2.5MHz
f
TEST
= 100kHz
V
S
= ±5V, f
CLK
= 500kHz
V
S
= ±5V, f
CLK
= 500kHz
V
S
= 4.75V, f
CLK
= 400kHz
V
S
= ±5V, I
SOURCE
/I
SINK
≤ 1mA, R
L
= 10k
V
S
= 4.75V, I
SOURCE
/I
SINK
≤ 1mA, R
L
= 10k
V
S
= ± 5V, f
CLK
= 500kHz
V
S
= 4.75V, f
CLK
= 400kHz
Note 1:
Stresses beyond those listed under Absolute Maximum Ratings
may cause permanent damage to the device. Exposure to any Absolute
Maximum Rating condition for extended periods may affect device
reliability and lifetime.
Note 2:
Phase Deviation = 1/2(Phase at 0Hz – Phase at f
CUTOFF
) – (Phase
at 0Hz – Phase at 0.5f
CUTOFF
)
Phase at 0Hz = 180° (guaranteed by design)
l
l
l
l
ELECTRICAL CHARACTERISTICS
MIN
–19
TYP
–16.5
MAX
–14
UNITS
dB
dB
dB
dB
dB
dB
dB
dB
dB
dB
–18.1
–20
–43
–55
–41
–48
–70
–59
–2.1
–35
–240
–30.5
–235
–3.0
50
25
±3.5
2.6
±4.0
3.6
18
13
26
29
15
16.5
–25
–230
–39
–55
–38
–17
Deg
Deg
Deg
mV
mV
V
V
P-P
mA
mA
mA
mA
125
Example: An LTC1069-7 has Phase at 0.5f
CUTOFF
= – 30.5° and Phase at
f
CUTOFF
= –235°.
Passband Phase Deviation from Linear Phase
= 1/2[180° – (–235°)] – [(180° – (–30.5°)] = –3°
10697fa
3
LTC1069-7
TYPICAL PERFORMANCE CHARACTERISTICS
Passband Gain vs Frequency
1.0
0.5
0
–0.5
V
S
= ±5V
f
CLK
= 500kHz
f
C
= 20kHz
V
IN
= 2V
RMS
Transition Band Gain vs Frequency
10
0
–10
GAIN (dB)
V
S
= ±5V
f
CLK
= 500kHz
f
C
= 20kHz
V
IN
= 2V
RMS
–40
–42
–44
–46
Stopband Gain vs Frequency
V
S
= ±5V
f
CLK
= 500kHz
f
C
= 20kHz
V
IN
= 2V
RMS
GAIN (dB)
–1.5
–2.0
–2.5
–3.0
–3.5
–4.0
1
3
5
7 9 11 13 15 17 19 21
FREQUENCY (kHz)
1069-7 G01
GAIN (dB)
21 23 25 27 29 31 33 35 37 39 41
FREQUENCY (kHz)
1069-7 G02
–1.0
–48
–50
–52
–54
–56
–58
–20
–30
–40
–50
–60
41 45 49 53 57 61 65 69 73 77 81
FREQUENCY (kHz)
1069-7 G03
Gain vs Frequency
10
0
–10
GAIN (dB)
–20
–30
–40
–50
–60
1
10
FREQUENCY (kHz)
100
1069-7 G04
Passband Gain
vs Clock Frequency
V
S
= ±5V
f
CLK
= 250kHz
f
C
= 10kHz
V
IN
= 1V
RMS
GAIN (dB)
3
0
–3
–6
–9
–12
–15
–18
20
f
CLK
= 2.5MHz
f
CLK
= 4.5MHz
f
CLK
= 4MHz
f
CLK
= 3.5MHz
f
CLK
= 3MHz
V
S
= ±5V
V
IN
= 2V
RMS
40
60
80 100 120 140 160 180 200
FREQUENCY (kHz)
1069-7 G05
Passband Gain vs Frequency
1.0
0.5
f
CLK
= 5MHz
0
–0.5
GAIN (dB)
–1.0
–1.5
–2.0
–2.5
–3.0
–3.5
–4.0
10
40
100
70
FREQUENCY (kHz)
130
160
1069-7 G06
V
S
= ±5V
f
CLK
= 4MHz
f
C
= 160kHz
V
IN
= 2V
RMS
T
A
= 85°C
T
A
= –40°C
T
A
= 25°C
Gain vs Supply Voltage
10
0
–10
GAIN (dB)
GAIN (dB)
–20
–30
–40
–50
–60
10 30 50 70 90 110 130 150 170 190 210
FREQUENCY (kHz)
1069-7 G07
Passband Gain
vs Clock Frequency
3
1.0
V
S
= 5V
V
IN
= 1V
RMS
0.5
0
–3
f
CLK
= 3MHz
–6
–9
–12
–15
–18
20
f
CLK
= 2.5MHz
f
CLK
= 2MHz
f
CLK
= 1.5MHz
40
60
80 100 120 140 160 180 200
FREQUENCY (kHz)
1069-7 G08
Passband Gain vs Frequency
f
CLK
= 2MHz
f
C
= 80kHz
V
IN
= 0.5V
RMS
0
–0.5
GAIN (dB)
–1.0
–1.5
–2.0
–2.5
–3.0
–3.5
–4.0
10 20
30
V
S
= 5V
f
CLK
= 2.5MHz
f
C
= 100kHz
V
IN
= 1V
RMS
T
A
= –40°C
T
A
= 25°C
T
A
= 85°C
V
S
= 5V
V
S
= ±5V
40 50 60 70
FREQUENCY (kHz)
80
90 100
1069-7 G09
10697fa
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LTC1069-7
TYPICAL PERFORMANCE CHARACTERISTICS
Passband Gain and Phase
vs Frequency
2
1
0
–1
GAIN (dB)
–2
–3
–4
–5
–6
–7
–8
0
PHASE
GAIN
V
S
= ±5V
f
CLK
= 2.5MHz
f
C
= 100kHz
180
135
90
45
PHASE (DEG)
GAIN (dB)
0
–45
–90
–135
–180
–225
–270
10 20 30 40 50 60 70 80 90 100
FREQUENCY (kHz)
1069-7 G10
Passband Gain and Delay
vs Frequency
2
1
0
–1
–2
–3
–4
–5
–6
–7
–8
0
11.0
10 20 30 40 50 60 70 80 90 100
FREQUENCY (kHz)
1069-7 G12
13.5
V
S
= ±5V
f
CLK
= 2.5MHz
f
C
= 100kHz
GAIN
13.0
DELAY (μs)
12.5
12.0
DELAY
11.5
Phase Matching vs Frequency
2.50
2.25
PHASE DIFFERENCE (DEG)
2.00
THD + NOISE (dB)
1.75
1.50
1.25
1.00
0.75
0.50
0.25
0
V
S
= ±5V
f
CLK
≤ 2.5MHz
PHASE DIFFERENCE BETWEEN
ANY TWO UNITS (SAMPLE OF
20 REPRESENTATIVE UNITS)
0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 1.0
FREQUENCY (f
CUTOFF
/FREQUENCY)
1069-7 G11
THD + Noise vs Input (V
P-P
)
–40
–40
f
CLK
= 1MHz
f
C
= 40kHz
f
IN
= 1kHz
THD + NOISE (dB)
–45
–50
–55
–60
–65
–70
V
S
= ±5V
–75
–80
0.1
1
INPUT (V
P-P
)
10
1609-7 G13
THD + Noise vs Frequency
f
CLK
= 2.5MHz
f
C
= 100kHz
70°C
–45
–50
–55
–60
–65
–70
–75
25°C
V
S
= 5V
V
S
= 5V, V
IN
= 1V
P-P
V
S
= ±5V, V
IN
= 2V
P-P
1
10
FREQUENCY (kHz)
100
1069-7 G14
Transient Response
–10
–15
OUTPUT OFFSET (mV)
Output Offset vs Clock Frequency
4.3
Output Voltage Swing
vs Temperature
1V/DIV
V
S
= 5V
–25
–30
–35
–40
–45
–50
0.25
V
S
= ±5V
VOLTAGE SWING (V)
–20
4.2
V
S
= 5V (AGND AT 2.5V)
f
CLK
= 500kHz
f
CUTOFF
= 20kHz
R
L
= 10k
I
SOURCE
/I
SINK
≤ 1mA
4.1
1.2
1.1
V
S
= ±5V
0.1ms/DIV
f
CLK
= 500kHz
f
CUTOFF
= 20kHz
V
IN
= 4V
P-P SQUARE WAVE AT 1kHZ
1069-7 G15
1.25
3.25
4.25
2.25
CLOCK FREQUENCY (MHz)
5.25
1.0
–40
–20
40
20
0
60
TEMPERATURE (°C)
80
100
1069-7 G16
1069-7 G17
10697fa
5
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