LTC1069-6
Single Supply, Very Low
Power, Elliptic Lowpass Filter
FEATURES
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DESCRIPTION
The LTC
®
1069-6 is a monolithic low power, 8th order lowpass
filter optimized for single 3V or single 5V supply operation.
The LTC1069-6 typically consumes 1mA under single 3V
supply operation and 1.2mA under 5V operation.
The cutoff frequency of the LTC1069-6 is clock tunable and it is
equal to the clock frequency divided by 50. The input signal is
sampled twice per clock cycle to lower the risk of aliasing.
The typical passband ripple is ± 0.1dB up to 0.9f
CUTOFF
.
The gain at f
CUTOFF
is –0.7dB. The transition band of the
LTC1069-6 features progressive attenuation reaching
42dB at 1.3f
CUTOFF
and 70dB at 2.1f
CUTOFF
. The maximum
stopband attenuation is 72dB.
The LTC1069-6 can be clock tuned for cutoff frequencies
up to 20kHz (single 5V supply) and for cutoff frequencies
up to 14kHz (single 3V supply).
The low power feature of the LTC1069-6 does not penalize
the device’s dynamic range. With single 5V supply and
an input range of 0.4V
RMS
to 1.4V
RMS
, the Signal-to-
(Noise + THD) ratio is ≥70dB. The wideband noise of the
LTC1069-6 is 125μV
RMS
.
Other filter responses with higher speed can be obtained.
Please contact LTC Marketing for details.
The LTC1069-6 is available in an 8-pin SO package.
8th Order Elliptic Filter in SO-8 Package
Single 3V Operation: Supply Current: 1mA (Typ)
f
CUTOFF
: 14kHz (Max) S/N Ratio: 72dB
Single 5V Operation: Supply Current: 1.2mA (Typ)
f
CUTOFF
: 20kHz (Max) S/N Ratio: 79dB
± 0.1dB Passband Ripple Up to 0.9f
CUTOFF
(Typ)
42dB Attenuation at 1.3f
CUTOFF
66dB Attenuation at 2.0f
CUTOFF
70dB Attenuation at 2.1f
CUTOFF
Wide Dynamic Range, 75dB or More (S/N + THD),
Under Single 5V Operation
Wideband Noise: 120µV
RMS
Clock-to-f
CUTOFF
Ratio: 50:1
Internal Sample Rate: 100:1
APPLICATIONS
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Handheld Instruments
Telecommunication Filters
Antialiasing Filters
Smoothing Filters
Audio
Multimedia
L,
LT, LTC and LTM are registered trademarks of Linear Technology Corporation.
TYPICAL APPLICATION
10
0
Frequency Response
V
IN
= 500mV
RMS
Single 3V Supply 10kHz Elliptic Lowpass Filter
GAIN (dB)
f
CLK
= 500kHz
1069-6 TA01
–10
–20
–30
–40
–50
–60
AGND
3V
0.47μF
0.1μF
NC
V
IN
V
+
V
OUT
V
–
LTC1069-6
NC
CLK
–70
–80
5
10
20
15
FREQUENCY (kHz)
25
1069-6 TA02
10696fa
1
LTC1069-6
ABSOLUTE MAXIMUM RATINGS
Total Supply Voltage (V
+
to V
–
) ................................12V
Operating Temperature Range
LTC1069-6C ............................................. 0°C to 70°C
LTC1069-6I ..........................................– 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
LTC1069-6CS8#PBF
LTC1069-6IS8#PBF
TAPE AND REEL
LTC1069-6CS8#TRPBF
LTC1069-6IS8#TRPBF
PART MARKING
10696
10696I
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/
ELECTRICAL CHARACTERISTICS
SYMBOL
Passband Gain (f
IN
≤ 0.2f
CUTOFF
)
CONDITIONS
The
l
denotes the specifications which apply over the full operating
temperature range.
f
CUTOFF
is the filter’s cutoff frequency and is equal to f
CLK
/50. The f
CLK
signal level is TTL or CMOS (clock rise or
fall time
≤
1µs) R
L
= 10k, V
S
= 5V, T
A
= 25°C, unless otherwise specified. All AC gains are measured relative to the passband gain.
MIN
l
l
l
l
l
l
l
l
l
l
TYP
0.1
0.1
0.1
0.1
0.07
0.07
0.07
0.07
0
0
0
0
0.1
0.1
0.1
0.1
0.05
0.05
0.05
0.05
MAX
0.45
0.50
0.45
0.50
0.25
0.30
0.25
0.30
0.25
0.30
0.25
0.30
0.45
0.45
0.45
0.50
0.25
0.25
0.25
0.35
UNITS
db
db
db
db
db
db
db
db
db
db
db
db
db
db
db
db
db
db
db
db
V
S
= 5V, f
CLK
= 200kHz
f
TEST
= 0.25kHz, V
IN
= 1V
RMS
V
S
= 3V, f
CLK
= 200kHz
f
TEST
= 0.25kHz, V
IN
= 0.5V
RMS
– 0.25
– 0.30
– 0.25
– 0.30
– 0.10
– 0.15
– 0.15
– 0.20
– 0.25
– 0.30
– 0.25
– 0.30
– 0.25
– 0.25
– 0.25
– 0.30
– 0.35
– 0.45
– 0.45
– 0.55
Gain at 0.50f
CUTOFF
V
S
= 5V, f
CLK
= 200kHz
f
TEST
= 2.0kHz, V
IN
= 1V
RMS
V
S
= 3V, f
CLK
= 200kHz
f
TEST
= 2.0kHz, V
IN
= 0.5V
RMS
Gain at 0.75f
CUTOFF
V
S
= 5V, f
CLK
= 200kHz
f
TEST
= 3.0kHz, V
IN
= 1V
RMS
V
S
= 3V, f
CLK
= 200kHz
f
TEST
= 3.0kHz, V
IN
= 0.5V
RMS
Gain at 0.90f
CUTOFF
V
S
= 5V, f
CLK
= 200kHz
f
TEST
= 3.6kHz, V
IN
= 1V
RMS
V
S
= 3V, f
CLK
= 200kHz
f
TEST
= 3.6kHz, V
IN
= 0.5V
RMS
Gain at 0.95f
CUTOFF
V
S
= 5V, f
CLK
= 200kHz
f
TEST
= 3.8kHz, V
IN
= 1V
RMS
V
S
= 3V, f
CLK
= 200kHz
f
TEST
= 3.8kHz, V
IN
= 0.5V
RMS
10696fa
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LTC1069-6
ELECTRICAL CHARACTERISTICS
SYMBOL
Gain at f
CUTOFF
CONDITIONS
V
S
= 5V, f
CLK
= 200kHz
f
TEST
= 4.0kHz, V
IN
= 1V
RMS
V
S
= 3V, f
CLK
= 200kHz
f
TEST
= 4.0kHz, V
IN
= 0.5V
RMS
Gain at 1.30f
CUTOFF
V
S
= 5V, f
CLK
= 200kHz
f
TEST
= 5.2kHz, V
IN
= 1V
RMS
V
S
= 3V, f
CLK
= 200kHz
f
TEST
= 5.2kHz, V
IN
= 0.5V
RMS
Gain at 2.00f
CUTOFF
V
S
= 5V, f
CLK
= 200kHz
f
TEST
= 8.0kHz, V
IN
= 1V
RMS
V
S
= 3V, f
CLK
= 200kHz
f
TEST
= 8.0kHz, V
IN
= 0.5V
RMS
Gain at 0.95f
CUTOFF
Output DC Offset (Note 1)
Output DC Offset Tempco
Output Voltage Swing (Note 2)
V
S
= 5V, f
CLK
= 400kHz, f
TEST
= 7.6kHz, V
IN
= 1V
RMS
V
S
= 3V, f
CLK
= 400kHz, f
TEST
= 7.6kHz, V
IN
= 0.5V
RMS
V
S
= 5V, f
CLK
= 100kHz
V
S
= 3V, f
CLK
= 100kHz
V
S
= 5V, V
S
= 3V
V
S
= 5V, f
CLK
= 100kHz
V
S
= 3V, f
CLK
= 100kHz
Power Supply Current
V
S
= 5V, f
CLK
= 100kHz
V
S
= 3V, f
CLK
= 100kHz
Maximum Clock Frequency
Input Frequency Range
Input Resistance
Operating Supply Voltage (Note 3)
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:
The input offset voltage is measured with respect to AGND (Pin 1).
The input (Pin 4) is also shorted to the AGND pin. The analog ground pin
potential is internally set to (0.437)(V
SUPPLY
).
V
S
= 5V
V
S
= 3V
0
35
3
50
l
l
l
l
l
l
l
l
l
l
The
l
denotes the specifications which apply over the full operating
temperature range.
f
CUTOFF
is the filter’s cutoff frequency and is equal to f
CLK
/50. The f
CLK
signal level is TTL or CMOS (clock rise or
fall time
≤
1µs) R
L
= 10k, V
S
= 5V, T
A
= 25°C, unless otherwise specified. All AC gains are measured relative to the passband gain.
MIN
– 1.50
– 1.65
– 1.5
– 1.7
TYP
–0.07
–0.07
–0.07
–0.07
–42
–42
–41
–41
–66
–66
–66
–66
– 0.5
– 0.5
0.15
0
50
30
30
3.4
3.2
1.6
1.6
4.2
4.2
2.0
2.0
1.2
1
1
0.7
<(f
CLK
– 2f
C
)
80
10
kΩ
V
1.60
1.65
1.40
1.55
MAX
–0.20
–0.25
0
0
–40
–39
–38
–37
–61
–60
–60
–59
0.5
0.5
175
135
UNITS
db
db
db
db
db
db
db
db
db
db
db
dB
db
db
mV
mV
μV/°C
V
P-P
V
P-P
V
P-P
V
P-P
mA
mA
mA
mA
MHz
MHz
Note 3:
The input voltage can swing to either rail (V
+
or ground); the
output typically swings 50mV from ground and 0.8V from V
+
.
Note 4:
The LTC1069-6 is optimized for 3V and 5V operation. Although
the device can operate with a single 10V supply or ±5V, the total harmonic
distortion will be degraded. For single 10V or ±5V supply operation we
recommend to use the LTC1069-1.
10696fa
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LTC1069-6
TYPICAL PERFORMANCE CHARACTERISTICS
Passband Gain vs Frequency
2
V
S
= SINGLE 3V
f
CLK
= 500kHz
f
CUTOFF
= 10kHz
V
IN
= 0.5V
RMS
GAIN (dB)
10
0
–10
–20
GAIN (dB)
–30
–40
–50
–60
–70
–80
–2
1
3
7
5
FREQUENCY (kHz)
9
11
1069-6 G01
Transition Band Gain
vs Frequency
–60
V
S
= SINGLE 3V
f
CLK
= 500kHz
f
CUTOFF
= 10kHz
V
IN
= 0.5V
RMS
GAIN (dB)
–62
–64
–66
–68
–70
–72
–74
–76
–78
–80
10
12
16
14
FREQUENCY (kHz)
18
20
1069-6 G02
Stopband Gain vs Frequency
V
S
= SINGLE 3V
f
CLK
= 500kHz
f
CUTOFF
= 10kHz
V
IN
= 0.5V
RMS
1
0
–1
–90
20
40
80
60
FREQUENCY (kHz)
100
1069-6 G03
Passband Gain vs Clock Frequency
2
V
S
= SINGLE 3V
V
IN
= 0.5V
RMS
1
GAIN (dB)
f
CLK
= 750kHz
f
CUTOFF
= 15kHz
GAIN (dB)
1
2
Passband Gain vs Clock Frequency
10
V
S
= SINGLE 5V
V
IN
= 1V
RMS
0
–10
–20
GAIN (db)
–30
–40
–50
–60
f
CLK
500kHz
f
CUTOFF
10kHz
1
3
5
f
CLK
750kHz
f
CUTOFF
15kHz
f
CLK
1MHz
f
CUTOFF
20kHz
–70
–80
–90
7 9 11 13 15 17 19 21
FREQUENCY (kHz)
1069-6 G05
Amplitude Response
vs Supply Voltage
f
CLK
= 500kHz
V
IN
= 0.5V
RMS
0
0
–1
f
CLK
= 500kHz
f
CUTOFF
= 10kHz
–1
SINGLE 5V
SINGLE 3V
–2
1
3
5
7 9 11 13 15 17 19 21
FREQUENCY (kHz)
1069-6 G04
–2
1
10
FREQUENCY (kHz)
100
1069-6 G06
Phase vs Frequency
90
0
–90
–180
PHASE (DEG)
–270
–360
–450
–540
–630
–720
–810
–900
0
2
4
8
6
10
FREQUENCY (kHz)
12
14
5.00E-05
0.00E+00
V
S
= SINGLE 5V
f
CLK
= 500kHz
f
CUTOFF
= 10kHz
GROUP DELAY (SEC)
4.00E-04
3.50E-04
3.00E-04
2.50E-04
2.00E-04
1.50E-04
1.00E-04
Group Delay vs Frequency
V
S
= SINGLE 5V
f
CLK
= 500kHz
f
CUTOFF
= 10kHz
0.5V/DIV
Transient Response
0
2
8
6
FREQUENCY (kHz)
4
10
12
V
S
= SINGLE 5V 0.1ms/DIV
f
CLK
= 1MHz
f
IN
= 1kHz
2V
p-p
SQUARE WAVE
1069-6 G09
1069-6 G07
1069-6 G08
10696fa
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LTC1069-6
TYPICAL PERFORMANCE CHARACTERISTICS
Dynamic Range THD + Noise
vs Input/Output Voltage
f
CLK
= 170kHz
–45 f
CUTOFF
= 3.4kHz
f = 1kHz
–50
IN
THD + NOISE (dB)
THD + NOISE (dB)
–55
–60
–65
–70
–75
–80
–85
–90
0.1
1
INPUT/OUTPUT VOLTAGE (V
P-P
)
3
1069-6 G14
Dynamic Range THD + Noise
vs Input Voltage
–40
–40
f
CLK
= 500kHz
–45 f
IN
= 1kHz
–50
V
S
= SINGLE 3V
V
S
=
SINGLE 5V
THD + NOISE (dB)
THD + Noise vs Frequency
f
CLK
= 500kHz
–45 f
CUTOFF
= 10kHz
–50
–55
–60
–65
–70
–75
–80
–85
–90
V
S
= SINGLE 5V
V
IN
= 1V
RMS
V
S
= SINGLE 3V
V
IN
= 0.5V
RMS
–40
V
IN
= 2.945V
P-P
–55
–60
–65
–70
–75
–80
–85
–90
0.1
0.5 0.76 1 1.43
INPUT VOLTAGE (V
RMS
)
5
1069-6 G10
1
5
FREQUENCY (kHz)
10
1069-6 G11
Supply Current vs Supply Voltage
POSITIVE SWING (V)
5
4.5
4.0
2.5
2.0
Output Voltage Swing
vs Temperature
R
L
= 10k
V
S
= SINGLE 5V
4
SUPPLY CURRENT (mA)
3
85°C
25°C
V
S
= SINGLE 3V
NEGATIVE SWING (mV)
2
80
60
40
20
0
–40
V
S
= SINGLE 5V
–20
0
20
40
60
AMBIENT TEMPERATURE (°C)
80
1069-6 G13
1
–40°C
V
S
= SINGLE 3V
0
0
2
8
6
4
10 12 14
TOTAL SUPPLY VOLTAGE (V)
16
1069-6 G12
PIN FUNCTIONS
AGND (Pin 1):
Analog Ground. The quality of the analog
signal ground can affect the filter performance. For either
single or dual supply operation, an analog ground plane
surrounding the package is recommended. The analog
ground plane should be connected to any digital ground
at a single point. For single supply operation, Pin 1 should
be bypassed to the analog ground plane with a 0.47μF
capacitor or larger. An internal resistive divider biases
Pin 1 to 0.4366 times the total power supply of the device
(Figure 1). That is, with a single 5V supply, the potential
at Pin 1 is 2.183V ±1%. As the LTC1069-6 is optimized
1
AGND
2 V
+
3
4
V
OUT
8
V
–
7
6
5
11.325k 8.775k
NC
LTC1069-6
V
IN
CLK
1069-6 F01
NC
Figure 1. Internal Biasing of the Analog Ground (Pin 1)
10696fa
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