LTC1062fd.pm7
1
LTC1062
1062fd
10Hz 5th Order Butterworth Lowpass Filter
Filter Amplitude Response and Noise
Lowpass Filter with No DC Error
Low Passband Noise
Operates DC to 20kHz
Operates On a Single 5V Supply or Up to ±8V
5th Order Filter
Maximally Flat Response
Internal or External Clock
Cascadable for Faster Rolloff
Buffer Available
The LTC
®
1062 is a 5th order all pole maximally flat
lowpass filter with no DC error. Its unusual architecture
puts the filter outside the DC path so DC offset and low
frequency noise problems are eliminated. This makes the
LTC1062 very useful for lowpass filters where DC accuracy
is important.
The filter input and output are simultaneously taken across
an external resistor. The LTC1062 is coupled to the signal
through an external capacitor. This RC reacts with the
internal switched capacitor network to form a 5th order
rolloff at the output.
The filter cutoff frequency is set by an internal clock that
can be externally driven. The clock-to-cutoff frequency
ratio is typically 100:1, allowing the clock ripple to be
easily removed.
Two LTC1062s can be cascaded to form a 10th order quasi
max flat lowpass filter. The device can be operated with
single or dual supplies ranging from ±2.5V to ±9V.
The LTC1062 is manufactured using Linear Technology's
enhanced LTCMOS
TM
silicon gate process.
60Hz Lowpass Filters
Antialiasing Filter
Low Level Filtering
Rolling Off AC Signals from High DC Voltages
Digital Voltmeters
Scales
Strain Gauges
LTCMOS is a trademark of Linear Technology Corporation.
FB
AGND
V
DIVIDER
RATIO
B
OUT
OUT
V
+
C
OSC
1
2
3
4
8
7
6
5
LTC1062
C
OSC=
3900pF
1062 TA01
1µF
V
IN
25.8k
V
+
= 5V
V
= 5V
DC ACCURATE
OUTPUT
BUFFERED
OUTPUT
NOTE: TO ADJUST OSCILLATOR FREQUENCY,
USE A 6800pF CAPACITOR IN SERIES
WITH A 50k POT FROM PIN 5 TO GROUND
INPUT FREQUENCY (Hz)
1
100
AMPLITUDE RESPONSE (dB) 80
60
40
20
10
100
1062 TA02
0
90
70
50
0
FILTER OUTPUT NOISE (
µ
V/
Hz)
20
40
10
30
50
30
10
C
OSC
= 3900pF
FEATURES
DESCRIPTIO
U
APPLICATIO S
U
TYPICAL APPLICATIO
U
, LTC and LT are registered trademarks of Linear Technology Corporation.
5th Order Lowpass Filter
2
LTC1062
1062fd
Total Supply Voltage (V
+
to V
) ............................... 18V
Input Voltage at Any Pin ..... V
0.3V V
IN
V
+
+ 0.3V
Operating Temperature Range
LTC1062M (OBSOLETE) ............. 55°C T
A
125°C
LTC1062C ................................... 40°C T
A
85°C
Storage Temperature Range ................. 65°C to 150°C
Lead Temperature (Soldering, 10 sec)................. 300°C
(Note 1)
The
denotes specifications which apply over the full operating tempera-
ture range, otherwise specifications are at T
A
= 25°C. V
+
= 5V, V
= 5V, unless otherwise specified. AC output measured at Pin 7,
Figure 1.
Consult LTC Marketing for parts specified with wider operating temperature ranges.
PARAMETER
CONDITIONS
MIN
TYP
MAX
UNITS
Power Supply Current
C
OSC
(Pin 5 to V
, Pin 11 in SW16) = 100pF
4.5
7
mA
10
mA
Input Frequency Range
0 to 20
kHz
Filter Gain at f
IN
= 0
f
CLK
= 100kHz, Pin 4 (Pin 6 in SW16) at V
+
,
0.00
dB
f
IN
= 0.5f
C
(Note 2)
C = 0.01µF, R = 25.78k
0.02 0.3
dB
f
IN
= f
C
2
3.00
dB
f
IN
= 2f
C
28
30.00
dB
f
IN
= 4f
C
52
60.00
dB
Clock-to-Cutoff Frequency Ratio, f
CLK
/f
C
f
CLK
= 100kHz, Pin 4 (Pin 6 in SW16) at V
+
,
100 ±1
%
C = 0.01µF, R = 25.78k
Filter Gain at f
IN
= 16kHz
f
CLK
= 400kHz, Pin 4 at V
+
, C = 0.01µF, R = 6.5k
43
52
dB
f
CLK
/f
C
Tempco
f
CLK
= 400kHz, Pin 4 at V
+
, C = 0.01µF, R = 6.5k
10
ppm/°C
Filter Output (Pin 7, Pin 13 in SW16) DC Swing
Pin 7/Pin13 (SW16) Buffered with an External Op Amp
±3.5
±3.8
V
Clock Feedthrough
1
mV
P-P
PACKAGE/ORDER I FOR ATIO
U
U
W
ORDER PART
NUMBER
LTC1062CN8
T
J MAX
= 100°C,
JA
= 130°C/W
T
J MAX
= 150°C,
JA
= 90°C/W
LTC1062CSW
ORDER PART
NUMBER
1
2
3
4
5
6
7
8
TOP VIEW
SW PACKAGE
16-LEAD PLASTIC SO
16
15
14
13
12
11
10
9
NC
NC
FB
AGND
V
NC
NC
NC
NC
B
OUT
OUT
V
+
C
OSC
NC
NC
DIVIDER
RATIO
1
2
3
4
8
7
6
5
TOP VIEW
FB
AGND
V
DIVIDER
RATIO
B
OUT
OUT
V
+
C
OSC
N8 PACKAGE
8-LEAD PDIP
J8 PACKAGE 8-LEAD CERDIP
T
J MAX
= 150°C,
JA
= 100°C/W
LTC1062MJ8
LTC1062CJ8
OBSOLETE PACKAGE
Consider the N8 Package as an Alternate Source
ELECTRICAL CHARACTERISTICS
ABSOLUTE AXI U RATI GS
W
W
W
U
3
LTC1062
1062fd
The
denotes specifications which apply over the full operating tempera-
ture range, otherwise specifications are at T
A
= 25°C. V
+
= 5V, V
= 5V, unless otherwise specified, AC output measured at Pin 7,
Figure 1.
PARAMETER
CONDITIONS
MIN
TYP
MAX
UNITS
Internal Buffer
Bias Current
2
50
pA
170
1000
pA
Offset Voltage
2
20
mV
Voltage Swing
R
LOAD
= 20k
±3.5
±3.8
V
Short-Circuit Current Source/Sink
40/3
mA
Clock (Note 3)
Internal Oscillator Frequency
C
OSC
(Pin 5 to V
, Pin 11 in SW16) = 100pF
25
32
50
kHz
15
65
kHz
Max Clock Frequency
4
MHz
Pin 5 (Pin 11 in SW16) Source or Sink Current
40
80
µA
Note 1: Absolute Maximum Ratings are those values beyond which the life of
a device may be impaired.
Note 2: f
C
is the frequency where the gain is 3dB with respect to the input
signal.
Note 3: The external or driven clock frequency is divided by either 1, 2 or 4
depending upon the voltage at Pin 4. For the N8 package, when Pin 4 = V
+
,
ratio = 1; when Pin 4 = GND, ratio = 2; when Pin 4 = V
, ratio = 4.
Amplitude Response Normalized
to the Cutoff Frequency
f
IN
/f
C
0.1
100
RESPONSE (dB)
80
60
40
20
1
10
1062 G01
0
90
70
50
30
10
1
2RC
=
V
S
= ±2.5V
T
A
= 25°C
f
C
1.62
f
CLK
= 500kHz, f
C
= 5kHz
f
CLK
= 250kHz, f
C
= 2.5kHz
f
CLK
= 100kHz, f
C
= 1kHz
f
CLK
= 1kHz, f
C
= 10Hz
f
CLK
= 10kHz, f
C
= 100Hz
f
IN
/f
C
0.1
100
RESPONSE (dB)
80
60
40
20
1
10
1062 G01
0
90
70
50
30
10
1
2RC
=
V
S
= ±2.5V
T
A
= 25°C
f
C
1.62
f
CLK
= 500kHz, f
C
= 5kHz
f
CLK
= 250kHz, f
C
= 2.5kHz
f
CLK
= 100kHz, f
C
= 1kHz
f
CLK
= 1kHz, f
C
= 10Hz
f
CLK
= 10kHz, f
C
= 100Hz
f
IN
/f
C
1.0
0.4
0.6
0.8
0.4
0.2
0
0.2
1062 G03
PASSBAND GAIN (dB)
0.1
0.2
0.4
0.6
0.8
1
V
S
= ±5V
T
A
= 25°C
f
CLK
= 100kHz
1
2RC
=
f
C
1.6
1
2RC
=
f
C
1.62
1
2RC
=
f
C
1.64
Amplitude Response Normalized
to the Cutoff Frequency
Passband Gain
vs Input Frequency
ELECTRICAL CHARACTERISTICS
TYPICAL PERFOR A CE CHARACTERISTICS
U
W
4
LTC1062
1062fd
Passband Gain
vs Input Frequency and Temperature
Passband Phase Shift
vs Input Frequency
Filter Noise Spectral Density
f
IN
/f
C
1.0
0.4
0.6
0.8
0.4
0.2
0
0.2
1062 G04
PASSBAND GAIN (dB)
0.1
0.2
0.4
0.6
0.8
1
V
S
= ±5V
f
CLK
= 100kHz
1
2RC
=
f
C
1.62
T
A
= 125°C
T
A
= 55°C
f
IN
/f
C
210
120
150
180
0
30
60
90
1062 G05
PHASE SHIFT (DEG)
0.1
0.2
0.4
0.6
0.8
1
V
S
= ±5V
f
CLK
= 100kHz
1
2RC
=
f
C
1.62
T
A
= 25°C
CUTOFF FREQUENCY (Hz)
20
FILTER OUTPUT NOISE (
µ
V/
Hz)
30
50
70
80
0.1
10
100
10k
1062 G06
10
1
1k
60
40
0
V
S
= ±5V
T
A
= 25°C
f
C
= 10Hz
f
C
= 1kHz
f
C
= 100Hz
Normalized Oscillator Frequency,
f
OSC
vs Supply Voltage
Oscillator Frequency, f
OSC
vs Ambient Temperature
V
SUPPLY
(V)
4
OSCILLATOR FREQUENCY NORMALIZED
TO f
OSC
AT 5V SUPPLY 1.1
1.2
1.3
20
1062 G07
1.0
0.9
0.7
8
12
16
18
6
10
14
0.8
1.6
1.5
1.4
AMBIENT TEMPERATURE (°C)
50
60
OSCILLATOR FREQUENCY (kHz)
80
120
140
160
260
200
0
50
75
1062 G08
100
220
240
180
25
25
100
125
C
OSC
= 0pF
V
+
= 10V
V
= 0V
V
+
= 5V
V
= 0V
Power Supply Current
vs Power Supply Voltage
POWER SUPPLY VOLTAGE (V)
4
SUPPLY CURRENT (mA)
8
12
20
1062 G09
4
0
8
12
16
6
10
14
18
16
6
10
2
14
T
A
= 55°C
T
A
= 25°C
T
A
= 125°C
TYPICAL PERFOR A CE CHARACTERISTICS
U
W
5
LTC1062
1062fd
8
7
6
5
1
2
3
4
SWITCHED
CAPACITOR
NETWORK
CLOCK GEN
÷ 1, 2, 4
OSC
B
OUT
OUT
V
+
C
OSC
1062 BD
÷
V
AGND
FB
f
CLK
×1
BY CONNECTING PIN 4 TO V
+
, AGND OR V
, THE
OUTPUT FREQUENCY OF THE INTERNAL CLOCK
GENERATOR IS THE OSCILLATOR FREQUENCY DI-
VIDED BY 1, 2, 4. THE (f
CLK
/f
C
) RATIO OF 100:1 IS
WITH RESPECT TO THE INTERNAL CLOCK GENERA-
TOR OUTPUT FREQUENCY. PIN 5 CAN BE DRIVEN
WITH AN EXTERNAL CMOS LEVEL CLOCK. THE
LTC1062 CAN ALSO BE SELF-CLOCKED BY CON-
NECTING AN EXTERNAL CAPACITOR (C
OSC
) TO
GROUND (OR TO V
IF C
OSC
IS POLARIZED). UNDER
THIS CONDITION AND WITH ±5V SUPPLIES, THE
INTERNAL OSCILLATOR FREQUENCY IS:
f
OSC
140kHz [33pF/(33pF + C
OSC
)]
AC TEST CIRCUIT
FB
AGND
V
DIVIDER
RATIO
B
OUT
OUT
V
+
C
OSC
1
2
3
4
8
7
6
5
LTC1062
0.1µF
MEASURED
OUTPUT
7
4
8
1
6
0.1µF
1062 F01
C = 0.01µF
V
IN
R = 25.8k
50
5V
5V
2
3
5V
5V
f
CLK
= 100kHz
5V
V
= 5V
R
+
LTC1052
1
2RC
FOR BEST MAX FLAT APPROXIMATION,
THE INPUT RC SHOULD BE SUCH AS:
A 0.5k RESISTOR, R, SHOULD BE USED IF
THE BIPOLAR EXTERNAL CLOCK IS APPLIED
BEFORE THE POWER SUPPLIES TURN ON
1
1.63
f
CLK
100
=
·
For Adjusting Oscillator Frequency, Insert a 50k Pot in Series with C
OSC
. Use Two Times Calculated C
OSC
Figure 1
BLOCK DIAGRA
W
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