LTC1065
DC Accurate, Clock-Tunable
Linear Phase 5th Order Bessel
Lowpass Filter
FEATURES
s
s
s
s
s
s
s
s
s
s
s
s
DESCRIPTIO
Clock-Tunable Cutoff Frequency
1mV DC Offset (Typical)
80dB CMR (Typical)
Internal or External Clock
50µV
RMS
Clock Feedthrough
100:1 Clock-to-Cutoff Frequency Ratio
80µV
RMS
Total Wideband Noise
0.004% Noise + THD at 2V
RMS
Output Level
50kHz Maximum Cutoff Frequency
Cascadable for Faster Roll-Off
Operates from
±2.375
to
±8V
Power Supplies
Self-Clocking with 1 RC
The LTC1065 is the first monolithic filter providing both
clock-tunability with low DC output offset and over 12-bit
DC accuracy. The frequency response of the LTC1065
closely approximates a 5th order Bessel polynomial. With
appropriate PCB layout techniques the output DC offset is
typically 1mV and is constant over a wide range of clock
frequencies. With
±5V
supplies and
±4V
input voltage
range, the CMR of the device is typically 80dB.
The filter cutoff frequency is controlled either by an inter-
nal or external clock. The clock-to-cutoff frequency ratio is
100 : 1. The on-board clock is nearly power supply inde-
pendent and it is programmed via an external RC. The
50µV
RMS
clock feedthrough of the device is considerably
lower than other existing monolithic filters.
The LTC1065 wideband noise is 80µV
RMS
and it can
process large AC input signals with low distortion. With
±
7.5V supplies, for instance, the filter handles up to
4V
RMS
(94dB S/N ratio) while the standard 1kHz THD is
below 0.005%; 87dB dynamic range (S/N + THD) is ob-
tained with input levels between 2V
RMS
and 2.5V
RMS
.
The LTC1065 is available in 8-pin miniDIP and 16-pin SOL.
For a Butterworth response, see LTC1063 data sheet. The
LTC1065 is pin compatible with the LTC1063.
APPLICATI
s
s
s
s
s
s
s
S
Audio
Strain Gauge Amplifiers
Anti-Aliasing Filters
Low Level Filtering
Digital Voltmeters
Smoothing Filters
Reconstruction Filters
TYPICAL APPLICATI
5V
4.99k
V
IN
1
2
3.4kHz Single 5V Supply Bessel Lowpass Filter
10
0
8
7
LTC1065
6
5
V
OUT
5V
0.1µF
–10
–20
GAIN (dB)
+
1µF
TANT
4.53k
0.1µF 3
4
–30
–40
–50
–60
13k*
*
SELF-CLOCKING SCHEME
200pF*
1065 TA01
–70
–80
–90
1
10
FREQUENCY (kHz)
100
1065 TA02
U
Frequency Response
UO
UO
1
LTC1065
ABSOLUTE
AXI U
RATI GS
Operating Temperature Range
LTC1065C.......................................... – 40°C to 85°C
LTC1065M ....................................... – 55°C to 125°C
Lead Temperature (Soldering, 10 sec)................. 300°C
Total Supply Voltage (V
+
to V
–
) .......................... 16.5V
Power Dissipation............................................. 400mW
Voltage at Any Input .... (V
–
– 0.3V)
≤
V
IN
≤
(V
+
+ 0.3V)
Burn-In Voltage ...................................................... 16V
Storage Temperature Range ................ – 65°C to 150°C
PACKAGE/ORDER I FOR ATIO
TOP VIEW
V
IN
1
GND 2
V
–
3
CLK OUT 4
8
7
6
5
V
OS
ADJ
V
OUT
V
+
CLK IN
ORDER PART
NUMBER
LTC1065CN8
LTC1065MJ8
J8 PACKAGE
8-LEAD CERAMIC DIP
N8 PACKAGE
8-LEAD PLASTIC DIP
T
JMAX
= 150°C,
θ
JA
= 100°C/W (J)
T
JMAX
= 100°C,
θ
JA
= 110°C/W (N)
ELECTRICAL CHARACTERISTICS
PARAMETER
Clock-to-Cutoff Frequency Ratio (f
CLK
/ f
C
)
Maximum Clock Frequency (Note 1)
V
S
=
±5V,
f
CLK
= 500kHz, f
C
= 5kHz, R
L
= 10k, T
A
= 25°C, unless otherwise specified.
CONDITIONS
±2.375V ≤
V
S
≤ ±7.5V
V
S
=
±7.5V
V
S
=
±5V
V
S
=
±2.5V
±2.5V ≤
V
S
≤ ±7.5V,
T
A
< 85°C
V
S
=
±5V,
f
CLK
= 25kHz, f
C
= 250Hz
f
IN
= 250Hz
f
IN
= 1kHz
V
S
=
±5V,
f
CLK
= 500kHz, f
C
= 5kHz
f
IN
= 100Hz
f
IN
= 1kHz = 0.2f
C
f
IN
= 2.5kHz = 0.5f
C
f
IN
= 4kHz = 0.8f
C
f
IN
= 5kHz = f
C
f
IN
= 10kHz = 2f
C
f
IN
= 20kHz = 4f
C
MIN
TYP
100
±
0.5
5
4
3
30
MAX
UNITS
MHz
MHz
MHz
Hz
0.9f
CLK
– 3.1
– 41.0
0
– 0.175
– 0.972
– 2.13
– 3.1
– 14.15
– 41.15
– 2.7
– 39.0
dB
dB
dB
dB
dB
dB
dB
dB
dB
Minimum Clock Frequency (Note 2)
Input Frequency Range
Filter Gain
2
U
U
W
W W
U
W
TOP VIEW
NC 1
V
IN
2
GND 3
NC 4
V
–
5
NC 6
NC 7
CLK OUT 8
16 V
OS
ADJ
15 NC
14 V
OUT
13 NC
12 V
+
11 NC
10 NC
9
S PACKAGE
16-LEAD PLASTIC SOL
CLK IN
ORDER PART
NUMBER
LTC1065CS
T
JMAX
= 100°C,
θ
JA
= 85°C/W
0
q
q
– 3.5
– 43.0
q
q
q
q
q
q
– 0.215
– 1.1
– 2.35
– 3.35
– 14.63
– 43.0
– 0.135
– 0.84
– 1.9
– 2.83
– 13.7
– 39.0
LTC1065
V
S
=
±5V,
f
CLK
= 500kHz, f
C
= 5kHz, R
L
= 10k, T
A
= 25°C, unless otherwise specified.
PARAMETER
Filter Gain
CONDITIONS
V
S
=
±2.375V,
f
CLK
= 500kHz, f
C
= 5kHz
f
IN
= 1kHz
f
IN
= 2.5kHz
f
IN
= 4kHz
f
IN
= 5kHz
f
IN
= 10kHz
±2.375V ≤
V
S
≤ ±7.5V
±2.375V ≤
V
S
≤ ±7.5V,
1Hz < f < f
CLK
V
S
=
±7.5V,
f
C
= 20kHz, f
IN
= 1kHz,
2V
RMS
≤
V
IN
≤
2.5V
RMS
V
S
=
±2.375V
V
S
=
±5V
q
ELECTRICAL CHARACTERISTICS
MIN
q
q
q
q
q
TYP
– 0.185
– 1.0
– 2.15
– 3.1
–14.1
50
80
– 87
1.7/– 2.2
4.3/– 4.8
6.8/– 7.3
10
800
2
0
–4
10
20
25
MAX
– 0.145
– 0.83
– 1.9
– 2.83
–13.7
UNITS
dB
dB
dB
dB
dB
µV
RMS
µV
RMS
dB
V
V
V
V
V
V
nA
MΩ
mV
mV
mV
µV/°C
µV/°C
µV/°C
kHz
kHz
kHz
kHz
kHz
khz
kHz
kHz
kHz
V
V
V
V
V
V
mA
mA
mA
mA
mA
mA
mA
mA
mA
– 0.225
– 1.1
– 2.35
– 3.35
– 14.63
Clock Feedthrough
Wideband Noise (Note 3)
THD + Wideband Noise (Note 4)
Filter Output
±
DC Swing
q
V
S
=
±7.5V
q
1.5/– 2.0
1.3/– 1.8
4.0/– 4.5
3.8/– 4.3
6.5/– 7.0
6.3/– 6.8
Input Bias Current
Dynamic Input Impedance
Output DC Offset (Note 5)
Output DC Offset Drift
Self-Clocking Frequency (f
OSC
)
External CLK Pin Logic Thresholds
Power Supply Current
V
S
=
±2.375V
V
S
=
±5V
V
S
=
±7.5V
V
S
=
±2.375V
V
S
=
±5V
V
S
=
±7.5V
R (Pin 4 to 5) = 20k, C (Pin 5 to GND) = 470pF
V
S
=
±2.375V
LTC1065C
LTC1065M
V
S
=
±5V
LTC1065C
LTC1065M
V
S
=
±7.5V
LTC1065C
LTC1065M
V
S
=
±2.375V
Min Logical “1”
Max Logical “0”
V
S
=
±5V
Min Logical “1”
Max Logical “0”
V
S
=
±7.5V
Min Logical “1”
Max Logical “0”
V
S
=
±2.375V,
f
CLK
= 500kHz
LTC1065C
LTC1065M
V
S
=
±5V,
f
CLK
= 500kHz
LTC1065C
LTC1065M
V
S
=
±7.5V,
f
CLK
= 500kHz
LTC1065C
LTC1065M
±5
q
q
q
q
q
q
99
95
92
100
98
97
102
101
100
103
103
100
106
106
105
106
109
108
1.43
0.47
3
1
4.5
1.5
2.5
112
112
112
112
114
114
114
116
116
q
q
5.5
q
q
7.0
q
q
4.0
5.5
6.0
9
11
12
12.0
14.5
16.0
3
LTC1065
ELECTRICAL CHARACTERISTICS
The
q
denotes specifications which apply over the full operating
temperature range.
Note 1:
The maximum clock frequency is arbitrarily defined as: the
frequency at which the filter AC response exhibits
≥
1dB of gain peaking.
Note 2:
At limited temperature ranges (i.e., T
A
≤
50°C) the minimum clock
frequency can be as low as 10Hz. The typical minimum clock frequency is
arbitrarily defined as: the clock frequency at which the output DC offset
changes by more than 1mV.
Note 3:
The wideband noise specification does not include the clock
feedthrough.
Note 4:
To properly evaluate the filter’s harmonic distortion an inverting
output buffer is recommended. An output buffer (although recommended)
is not necessarily needed when measuring output DC offset or wideband
noise (see Figure 3).
Note 5:
The output DC offset is optimized for
±5V
supply. The output DC
offset shifts when the power supplies change; however this phenomenon
is repeatable and predictable.
TYPICAL PERFOR A CE CHARACTERISTICS
Self-Clocking Frequency vs R
110
100
LTC1065
90
4
R
OUTPUT OFFSET (mV)
R PINS 4 TO 5 (kΩ)
80
70
60
50
40
30
20
10
100
300
FREQUENCY (kHz)
500
1065 G01
35
30
25
20
15
10
5
0
10
OUTPUT OFFSET (mV)
C = 200pF
f
OSC
≅
1/RC
Gain vs Frequency; V
S
=
±2.5V
10
0
–10
–20
GAIN (dB)
GAIN (dB)
–40
–50
–60
–70
–80
–90
1
V
IN
= 750mV
RMS
T
A
= 25°C
A. f
CLK
= 0.5MHz
B. f
CLK
= 1MHz
C. f
CLK
= 2MHz
A
B
C
–40
–50
–60
–70
–80
–90
V
IN
= 1.4V
RMS
T
A
= 25°C
1
A. f
CLK
= 1MHz
B. f
CLK
= 2MHz
C. f
CLK
= 3MHz
D. f
CLK
= 4MHz
A
B C
D
GAIN (dB)
–30
10
INPUT FREQUENCY (kHz)
4
U W
5
C
Output Offset vs Clock,
Low Clock Rates
50
45
40
V
S
= ±5V
A. T
A
= 25°C
B. T
A
= 85°C
Output Offset vs Clock,
Medium Clock Rates
5
4
3
2
1
0
–1
–2
–3
V
S
= ±2.5V
V
S
= ±5V
V
S
= ±7.5V
B
A
110
EXTERNAL CLOCK FREQUENCY (Hz)
210
–4
–5
0
500
1000
EXTERNAL CLOCK FREQUENCY (kHz)
1065 G03
1065 G02
Gain vs Frequency; V
S
=
±5V
10
0
–10
–20
–30
10
0
Gain vs Frequency; V
S
=
±7.5V
D
–10
–20
–30
–40
–50
–60
–70
–80
–90
V
IN
= 1.4V
RMS
T
A
= 25°C
1
10
INPUT FREQUENCY (kHz)
100 200
1065 G06
A
B C
E
A. f
CLK
= 1MHz
B. f
CLK
= 2MHz
C. f
CLK
= 3MHz
D. f
CLK
= 4MHz
E.f
CLK
= 5MHz
100 200
1065 G04
10
INPUT FREQUENCY (kHz)
100 200
1065 G05
LTC1065
TYPICAL PERFOR A CE CHARACTERISTICS
THD + Noise vs Input Voltage;
V
S
= Single 5V, AGND = 2V
1
f
IN
= 1kHz, T
A
= 25°C
1
V
IN
= 0.75V
RMS
, S/N = 80dB
f
C
= 5kHz, f
CLK
= 500kHz
T
A
= 25°C
0.1
THD (%)
THD + NOISE (%)
0.1
THD + NOISE (%)
B
0.01
A
A. f
C
= 5kHz, f
CLK
= 0.5MHz
B. f
C
= 10kHz, f
CLK
= 1MHz
0.001
0.1
0.001
1
INPUT (V
RMS
)
THD vs Frequency; V
S
=
±5V
1
V
IN
= 1.5V
RMS
f
C
= 10kHz, f
CLK
= 1MHz
T
A
= 25°C
0.1
THD (%)
THD + NOISE (%)
0.01
0.01
B
A
A. f
C
= 10kHz, f
CLK
= 1MHz
B. f
C
= 20kHz, f
CLK
= 2MHz
THD (%)
0.001
1
5
FREQUENCY (kHz)
10
1065 G10
Passband Gain and Phase
vs Input Frequency
1
0
±2.5V
≤
V
S
≤
±7.5V, T
A
= 25°C
40
0
–40
PHASE MISMATCH (±DEG)
POWER SUPPLY CURRENT (mA)
PASSBAND GAIN (dB)
–1
–2
–3
–4
–5
–6
100
f
C
=1kHz
f
CLK
=100kHz
A
PHASE
A
B
PHASE
B
–160
f
C
=10kHz
f
CLK
=1MHz
–200
–240
100k
1065 G13
1k
10k
INPUT FREQUENCY (Hz)
U W
5
1065 G07
THD vs Frequency;
V
S
= Single 5V, AGND = 2V
1
THD + Noise vs Input Voltage;
V
S
=
±5V
f
IN
= 1kHz, T
A
= 25°C
0.1
B
0.01
0.01
A
A. f
C
= 10kHz, f
CLK
= 1MHz
B. f
C
= 20kHz, f
CLK
= 2MHz
1
2
3
FREQUENCY (kHz)
4
5
1065 G08
0.001
0.1
1
INPUT (V
RMS
)
5
1065 G09
THD + Noise vs Input Voltage;
V
S
=
±7.5V
1
f
IN
= 1kHz
T
A
= 25°C
THD vs Frequency;
V
S
=
±7.5V
1
V
IN
= 2.5V
RMS
, S/N = 90dB
f
C
= 10kHz, f
CLK
= 1MHz
T
A
= 25°C
0.1
0.1
0.01
0.001
0.1
1
INPUT (V
RMS
)
5
1065 G11
0.001
1
5
FREQUENCY (kHz)
10
1065 G12
Typical Phase Matching
Device to Device
0.6
0.5
0.4
0.3
0.2
0.1
0
V
S
= ± 7.5V
V
IN
= 1V
RMS
f
C
= 20kHz
f
CLK
= 2MHz
15
Power Supply Current vs
Power Supply Voltage
–40°C
12
25°C
9
85°C
6
PHASE (DEG)
–80
–120
3
0 2
4
6 8 10 12 14 16 18 20 22 24
INPUT FREQUENCY (kHz)
1065 G14
0
0
2 4 6 8 10 12 14 16 18 20
TOTAL POWER SUPPLY VOLTAGE (V)
1065 G15
5
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