LTC1069-7
Linear Phase
8th Order Lowpass Filter
FEATURES
s
s
s
s
s
s
s
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 shap-
ing 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 specifica-
tions can be obtained. Please contact LTC Marketing.
, LTC and LT are registered trademarks of Linear Technology Corporation.
APPLICATIONS
s
s
s
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
10
Single 5V Supply, Linear Phase 100kHz Lowpass Filter
AGND
5V
0.47µF
0.1µF
NC
V
IN
V
IN
V
+
LTC1069-7
NC
CLK
f
CLK
= 2.5MHz
1069-7 TA01
V
OUT
V
–
GAIN (dB)
U
U
U
0
–10
–20
– 30
– 40
– 50
– 60
–70
10
100
FREQUENCY (kHz)
1000
1069-7 TA02
V
OUT
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
PACKAGE/ORDER INFORMATION
TOP VIEW
AGND 1
V
+
2
NC 3
V
IN
4
8
7
6
5
V
OUT
V
–
NC
CLK
ORDER PART
NUMBER
LTC1069-7CS8
LTC1069-7IS8
S8 PART MARKING
10697
10697I
S8 PACKAGE
8-LEAD PLASTIC SO
T
JMAX
= 125°C,
θ
JA
= 110°C/ W
Consult factory for Military grade parts.
ELECTRICAL CHARACTERISTICS
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.
PARAMETER
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
Gain at 1.5f
CUTOFF
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
q
MIN
TYP
– 0.10
– 0.10
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
dB
dB
dB
dB
dB
dB
dB
dB
q
– 0.30
q
q
q
q
q
q
q
q
q
q
q
q
– 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
– 16.5
– 19
– 18.1
– 20
– 43
– 55
– 41
– 48
0.15
– 0.35
0
– 0.80
– 0.25
– 2.7
– 2.4
– 14
– 17
– 38
– 39
2
U
W
U
U
W W
W
LTC1069-7
ELECTRICAL CHARACTERISTICS
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.
PARAMETER
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
CONDITIONS
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
q
q
q
MIN
– 70
TYP
–59
– 2.1
MAX
– 55
UNITS
dB
dB
– 35
– 240
– 30.5
– 235
– 3.0
50
25
– 25
– 230
Deg
Deg
Deg
mV
mV
V
V
P-P
125
±3.5
2.6
±4.0
3.6
18
13
26
29
15
16.5
mA
mA
mA
mA
V
S
= 4.75V, f
CLK
= 400kHz
q
The
q
denotes specifications which apply over the full operating
temperature range.
Note 1:
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)
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°
TYPICAL PERFORMANCE CHARACTERISTICS
Passband Gain vs Frequency
1.0
0.5
0
–0.5
10
V
S
=
±5V
f
CLK
= 500kHz
f
C
= 20kHz
V
IN
= 2V
RMS
0
–10
GAIN (dB)
GAIN (dB)
–1.5
–2.0
–2.5
–3.0
–3.5
–4.0
–20
–30
–40
–50
GAIN (dB)
–1.0
1
3
5
7 9 11 13 15 17 19 21
FREQUENCY (kHz)
LTC1069-7 • TPC01
U W
Transition Band Gain vs Frequency
V
S
=
±5V
f
CLK
= 500kHz
f
C
= 20kHz
V
IN
= 2V
RMS
–40
–42
–44
–46
–48
–50
–52
–54
–56
–58
Stopband Gain vs Frequency
V
S
=
±5V
f
CLK
= 500kHz
f
C
= 20kHz
V
IN
= 2V
RMS
21 23 25 27 29 31 33 35 37 39 41
FREQUENCY (kHz)
LTC1069-7 • TPC02
–60
41 45 49 53 57 61 65 69 73 77 81
FREQUENCY (kHz)
LTC1069-7 • TPC03
3
LTC1069-7
TYPICAL PERFORMANCE CHARACTERISTICS
Gain vs Frequency
10
0
–10
GAIN (dB)
V
S
=
±5V
f
CLK
= 250kHz
f
C
= 10kHz
V
IN
= 1V
RMS
GAIN (dB)
–20
–30
–40
–50
–60
1
10
FREQUENCY (kHz)
100
LTC1069-7 • TPC04
–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)
LTC1069-7 • TPC05
GAIN (dB)
Gain vs Supply Voltage
10
0
–10
f
CLK
= 2MHz
f
C
= 80kHz
V
IN
= 0.5V
RMS
GAIN (dB)
GAIN (dB)
–20
–30
–40
–50
–60
10 30 50 70 90 110 130 150 170 190 210
FREQUENCY (kHz)
LTC1069-7 • TPC07
–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)
LTC1069-7 • TPC08
GAIN (dB)
V
S
=
±5V
Passband Gain and Phase vs
Frequency
2
1
0
–1
GAIN (dB)
GAIN
GAIN (dB)
–2
–3
–4
–5
–6
–7
–8
0
PHASE
–270
10 20 30 40 50 60 70 80 90 100
FREQUENCY (kHz)
LTC1069-7 • TPC10
4
U W
V
S
= 5V
Passband Gain vs
Clock Frequency
3
0
–3
f
CLK
= 5MHz
Passband Gain vs Frequency
1.0
0.5
0
–0.5
–1.0
–1.5
–2.0
–2.5
–3.0
–3.5
–4.0
10
40
100
70
FREQUENCY (kHz)
130
160
T
A
= –40°C
T
A
= 25°C
T
A
= 85°C
V
S
=
±5V
f
CLK
= 4MHz
f
C
= 160kHz
V
IN
= 2V
RMS
LTC1069-7 • TPC06
Passband Gain vs
Clock Frequency
3
0
–3
f
CLK
= 3MHz
V
S
= 5V
V
IN
= 1V
RMS
1.0
0.5
0
–0.5
–1.0
–1.5
–2.0
–2.5
–3.0
–3.5
–4.0
Passband Gain vs Frequency
T
A
= 85°C
T
A
= –40°C
T
A
= 25°C
V
S
= 5V
f
CLK
= 2.5MHz
f
C
= 100kHz
V
IN
= 1V
RMS
10 20
30
40 50 60 70
FREQUENCY (kHz)
80
90 100
LTC1069-7 • TPC09
Passband Gain and Delay vs
Frequency
180
135
90
45
PHASE (DEG)
2
1
0
–1
GAIN
–2
–3
–4
–5
–6
–7
–8
0
DELAY
V
S
=
±5V
f
CLK
= 2.5MHz
f
C
= 100kHz
V
S
=
±5V
f
CLK
= 2.5MHz
f
C
= 100kHz
13.5
13.0
DELAY (µs)
0
–45
–90
–135
–180
–225
12.5
12.0
11.5
11.0
10 20 30 40 50 60 70 80 90 100
FREQUENCY (kHz)
LTC1069-7 • TPC12
LTC1069-7
TYPICAL PERFORMANCE CHARACTERISTICS
Phase Matching vs Frequency
2.50
2.25
PHASE DIFFERENCE (DEG)
70°C
2.00
THD + NOISE (dB)
25°C
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)
LTC1069-7 • TPC11
Transient Response
–10
–15
OUTPUT OFFSET (mV)
1V/DIV
V
S
= 5V
–25
–30
–35
–40
–45
–50
0.25
V
S
=
±5V
VOLTAGE SWING (V)
V
S
=
±5V
0.1ms/DIV
f
CLK
= 500kHz
f
CUTOFF
= 20kHz
V
IN
= 4V
P-P
SQUARE WAVE AT 1kHz
Output Voltage Swing vs
Temperature
4.2
4.1
SUPPLY CURRENT (mA)
VOLTAGE SWING (V)
20
15
10
5
0
–40°C
SUPPLY CURRENT (mA)
4.0
–4.5
V
S
=
±5V
f
CLK
= 2.5MHz
f
CUTOFF
= 100kHz
R
L
= 10k
I
SOURCE
/I
SINK
= 1mA
–4.6
–4.7
–40 –20
40
20
0
60
TEMPERATURE (°C)
U W
80
LTC1069-7 • TPC18
THD + Noise vs Input (V
P-P
)
–40
–45
–50
–55
–60
–65
–70
–75
0.1
1
INPUT (V
P-P
)
10
LTC1609-7 • TPC13
THD + Noise vs Frequency
–40
–45
–50
–55
–60
–65
–70
V
S
= 5V, V
IN
= 1V
P-P
f
CLK
= 2.5MHz
f
C
= 100kHz
f
CLK
= 1MHz
f
C
= 40kHz
f
IN
= 1kHz
V
S
= 5V
V
S
=
±5V
–75
–80
1
V
S
=
±5V,
V
IN
= 2V
P-P
10
FREQUENCY (kHz)
100
LTC1069-7 • TPC14
Output Offset vs Clock Frequency
4.3
Output Voltage Swing vs
Temperature
–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
LTC1069-7 • TPC15
1.1
1.25
3.25
4.25
2.25
CLOCK FREQUENCY (MHz)
5.25
1.0
–40 –20
40
20
60
0
TEMPERATURE (°C)
80
100
LTC1069-7 • TPC16
LTC1069-7 • TPC17
Supply Current vs
Supply Voltage
22
Supply Current vs
Clock Frequency
21
25
f
CLK
= 10Hz
25°C
85°C
20
19
18
17
16
15
14
13
12
11
V
S
= 5V
1.25
2.25
3.25
4.25
CLOCK FREQUENCY (MHz)
5.25
10
0.25
V
S
=
±5V
100
0
1
4
2
3
SUPPLY VOLTAGE (±V)
5
6
LTC1069-7 • TPC19
LTC1263 • TPC20
5
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