LTC1562-2
Very Low Noise, Low Distortion
Active RC Quad Universal Filter
FEATURES
s
s
DESCRIPTIO
s
s
s
s
s
s
s
s
s
s
Continuous Time—No Clock
Four 2nd Order Filter Sections, 20kHz to 300kHz
Center Frequency
Butterworth, Chebyshev, Elliptic or Equiripple
Delay Response
Lowpass, Bandpass, Highpass Responses
99dB Typical S/N,
±5V
Supply (Q = 1)
93dB Typical S/N, Single 5V Supply (Q = 1)
Rail-to-Rail Input and Output Voltages
DC Accurate to 3mV (Typ)
±0.5%
Typical Center Frequency Accuracy
“Zero-Power” Shutdown Mode
Single or Dual Supply, 5V to 10V Total
Resistor-Programmable f
O
, Q, Gain
APPLICATIO S
s
s
s
s
s
s
High Resolution Systems (14 Bits to 18 Bits)
Antialiasing/Reconstruction Filters
Data Communications, Equalizers
Dual or I-and-Q Channels (Two Matched 4th Order
Filters in One Package)
Linear Phase Filtering
Replacing LC Filter Modules
The LTC
®
1562-2 is a low noise, low distortion continuous
time filter with rail-to-rail inputs and outputs, optimized for a
center frequency (f
O
) of 20kHz to 300kHz. Unlike most
monolithic filters, no clock is needed. Four independent 2nd
order filter blocks can be cascaded in any combination, such
as one 8th order or two 4th order filters. Each block’s
response is programmed with three external resistors for
center frequency, Q and gain, using simple design formulas.
Each 2nd order block provides lowpass and bandpass out-
puts. Highpass response is available if an external capacitor
replaces one of the resistors. Allpass, notch and elliptic
responses can also be realized.
The LTC1562-2 is designed for applications where dynamic
range is important. For example, by cascading 2nd order
sections in pairs, the user can configure the IC as a dual 4th
order Butterworth lowpass filter with 90dB signal-to-noise
ratio from a single 5V power supply. Low level signals can
exploit the built-in gain capability of the LTC1562-2. Varying
the gain of a section can achieve a dynamic range as high as
114dB with a
±5V
supply.
Other cutoff frequency ranges can be provided upon request.
Please contact LTC Marketing.
, LTC and LT are registered trademarks of Linear Technology Corporation.
TYPICAL APPLICATIO
Dual 4th Order 200kHz Butterworth Lowpass Filter, SNR 96dB
R
IN2
7.87k
R
IN1
7.87k
V
IN1
R
Q1
4.22k
R21 7.87k
5V
0.1µF
R23 7.87k
R
Q3
4.22k
R
IN3
7.87k
V
IN2
*V
–
ALSO AT PINS 4, 7, 14 & 17
ALL RESISTORS 1% METAL FILM
1
2
3
5
6
8
9
10
20
19
18
16
15
13
12
11
R
IN4
7.87k
1562-2 TA01
10
V
OUT1
R
Q2
10.2k
R22 7.87k
– 5V*
0.1µF
R24 7.87k
R
Q4
10.2k
GAIN (dB)
0
–10
–20
–30
–40
–50
–60
–70
–80
50k
100k
FREQUENCY (Hz)
1562-2 TA02
INV B
V1 B
V2 B
V
+
INV C
V1 C
V2 C
LTC1562-2 V
–
AGND
V2 D
V1 D
INV D
SHDN
V2 A
V1 A
INV A
V
OUT2
U
Amplitude Response
1M
1.5M
15622fa
U
U
1
LTC1562-2
ABSOLUTE
(Note 1)
AXI U
RATI GS
PACKAGE/ORDER I FOR ATIO
TOP VIEW
INV B
V1 B
V2 B
V
–*
V
+
SHDN
V
–*
V2 A
V1 A
INV A
1
2
3
4
5
6
7
8
9
10
20
19
18
17
16
15
14
13
12
11
INV C
V1 C
V2 C
V
–*
V
–
AGND
V
–*
V2 D
V1 D
INV D
Total Supply Voltage (V
+
to V
–
) .............................. 11V
Maximum Input Voltage
at Any Pin ....................(V
–
– 0.3V)
≤
V
≤
(V
+
+ 0.3V)
Storage Temperature Range ................. – 65°C to 150°C
Operating Temperature Range
LTC1562C-2 ............................................ 0°C to 70°C
LTC1562I-2 ........................................ – 40°C to 85°C
Lead Temperature (Soldering, 10 sec).................. 300°C
ORDER PART
NUMBER
LTC1562CG-2
LTC1562IG-2
G PACKAGE
20-LEAD PLASTIC SSOP
*G PACKAGE PINS 4, 7, 14, 17 ARE
SUBSTRATE/SHIELD CONNECTIONS
AND MUST BE TIED TO V
–
T
JMAX
= 150°C,
θ
JA
= 136°C/W
Consult LTC Marketing for parts specified with wider operating temperature ranges.
ELECTRICAL CHARACTERISTICS
SYMBOL
V
S
I
S
PARAMETER
Total Supply Voltage
Supply Current
The
q
denotes specifications that apply over the full operating temperature
range, otherwise specifications are at T
A
= 25°C. V
S
=
±5V,
outputs unloaded, SHDN pin to logic “low”, unless otherwise noted. AC
specs are for a single 2nd order section, R
IN
= R2 = 10.4k
±0.1%,
R
Q
= 9.09k
±0.1%,
f
O
= 175kHz.
CONDITIONS
V
S
=
±2.375V,
R
L
= 5k, C
L
= 30pF, Outputs at 0V
V
S
=
±5V,
R
L
= 5k, C
L
= 30pF, Outputs at 0V
V
S
=
±2.375V,
R
L
= 5k, C
L
= 30pF, Outputs at 0V
V
S
=
±5V,
R
L
= 5k, C
L
= 30pF, Outputs at 0V
Output Voltage Swing, V2 Outputs
Output Voltage Swing, V1 Outputs
V
OS
DC Offset Magnitude, V2 Outputs
DC AGND Reference Point
Center Frequency (f
O
) Error (Notes 2, 3)
H
L
Lowpass Passband Gain at V2 Output
Q Accuracy
Wideband Output Noise
Input-Referred Noise, Gain = 100
V
S
=
±2.375V,
R
L
= 5k, C
L
= 30pF
V
S
=
±5V,
R
L
= 5k, C
L
= 30pF
V
S
=
±2.375V,
R
L
= 5k, C
L
= 30pF, f = 250kHz
V
S
=
±5V,
R
L
= 5k, C
L
= 30pF, f = 250kHz
V
S
=
±2.375V,
Input at AGND Voltage
V
S
=
±5V,
Input at AGND Voltage
V
S
= Single 5V Supply
V
S
=
±5V,
V2 Output Has R
L
= 5k, C
L
= 30pF
V
S
=
±2.375V,
f
IN
= 10kHz,
V2 Output Has R
L
= 5k, C
L
= 30pF
V
S
=
±2.375V,
V2 Output Has R
L
= 5k, C
L
= 30pF
V
S
=
±2.375V,
BW = 400kHz, Input AC GND
V
S
=
±5V,
BW = 400kHz, Input AC GND
BW = 400kHz, f
O
= 200kHz, Q = 1, Input AC GND
q
q
q
q
q
MIN
4.75
TYP
21
22.5
MAX
10.5
23.5
25
28
30
UNITS
V
mA
mA
mA
mA
V
P-P
V
P-P
V
P-P
V
P-P
4.2
9.3
8.4
4.6
9.8
4.5
9.7
3
3
2.5
0.5
1.7
+ 0.1
17
17
0
+ 0.05
+2
39
39
7.3
µV
RMS
µV
RMS
µV
RMS
15622fa
2
U
mV
mV
V
%
dB
%
W
U
U
W W
W
LTC1562-2
The
q
denotes specifications that apply over the full operating temperature
range, otherwise specifications are at T
A
= 25°C. V
S
=
±5V,
outputs unloaded, SHDN pin to logic “low”, unless otherwise noted. AC
specs are for a single 2nd order section, R
IN
= R2 = 10.4k
±0.1%,
R
Q
= 9.09k
±0.1%,
f
O
= 175kHz.
SYMBOL
THD
PARAMETER
Total Harmonic Distortion, V2 Output
CONDITIONS
f
IN
= 20kHz, 2.8V
P-P
, V1 and V2 Outputs Have
R
L
= 5k, C
L
= 30pF
f
IN
= 20kHz, 9V
P-P
, V1 and V2 Outputs Have
R
L
= 5k, C
L
= 30pF
Shutdown Supply Current
Shutdown-Input Logic Threshold
Shutdown-Input Bias Current
Shutdown Delay
Shutdown Recovery Delay
Inverting Input Bias Current, Each Biquad
Note 1:
Absolute Maximum Ratings are those values beyond which the life
of a device may be impaired.
Note 2:
f
O
change from
±5V
to
±2.375
supplies is – 0.2% typical,
f
O
temperature coefficient magnitude, 25°C to 85°C, is
50ppm/°C typical.
As with the LTC1562, f
O
decreases with increasing temperature.
SHDN Pin to 0V
SHDN Pin Steps from 0V to V
+
SHDN Pin Steps from
V
+
to 0V
SHDN Pin to V
+
SHDN Pin to V
+
, V
S
=
±2.375V
MIN
TYP
– 100
– 82
1.5
1.0
2.5
– 10
20
100
5
Note 3:
Tighter frequency tolerance is available, consult factory.
– 20
15
MAX
UNITS
dB
dB
µA
µA
V
µA
µs
µs
pA
ELECTRICAL CHARACTERISTICS
TYPICAL PERFOR A CE CHARACTERISTICS
f
O
Error vs Nominal f
O
(V
S
=
±5V)
3.0
3.0
T = 25°C
2.5 R
A
= R
IN
Q
2.0
1.5
f
O
ERROR (%)
f
O
ERROR (%)
Q ERROR (%)
1.0
0.5
0
– 0.5
–1.0
–1.5
–2.0
–2.5
–3.0
120 140 160 180 200 220 240 260 280
NOMINAL f
O
(kHz)
1562-2 G01
Q=5
Q = 2.5
U W
Q=1
f
O
Error vs Nominal f
O
(V
S
=
±2.5V)
45
40
35
30
Q=5
25
20
15
10
5
Q=1
0
T = 25°C
2.5 R
A
= R
IN
Q
2.0
1.5
1.0
0.5
0
– 0.5
–1.0
–1.5
–2.0
–2.5
Q = 2.5
Q Error vs Nominal f
O
(V
S
=
±5V)
T
A
= 70°C
T
A
= 25°C
R
IN
= R
Q
Q=5
Q = 2.5
Q=1
–3.0
120 140 160 180 200 220 240 260 280
NOMINAL f
O
(kHz)
1562-2 G02
–5
100 120 140 160 180 200 220 240 260 280 300
NOMINAL f
O
(kHz)
1562-2 G03
15622fa
3
LTC1562-2
TYPICAL PERFOR A CE CHARACTERISTICS
Q Error vs Nominal f
O
(V
S
=
±2.5V)
55
50
45
40
Q ERROR (%)
3.00
T
A
= 70°C
T
A
= 25°C
R
IN
= R
Q
Q=5
PEAK BP GAIN (dB)
35
30
25
20
15
10
5
0
–5
100 120 140 160 180 200 220 240 260 280 300
NOMINAL f
O
(kHz)
1562-2 G04
2.00
1.75
1.50
1.25
1.00
0.75
0.50
0.25
0
100 120 140 160 180 200 220 240 260 280 300
NOMINAL f
O
(kHz)
1562-2 G5
Q = 2.5
Q=1
Q = 2.5
Q=1
PEAK BP GAIN (dB)
LP Noise vs Nominal f
O
(V
S
=
±5V,
25°C) (Figure 3,
V2 Output) (R
IN
= R2)
100
90
80
100
90
80
BP NOISE (µV
RMS
)
THD (AMPLITUDE BELOW FUNDAMENTAL) (dB)
LP NOISE (µV
RMS
)
70
60
50
40
30
20
Q=5
Q = 2.5
Q=1
10
120 140 160 180 200 220 240 260 280
NOMINAL f
O
(kHz)
1562-2 G07
PIN FUNCTIONS
Power Supply Pins:
The V
+
and V
–
pins should be
bypassed with 0.1µF capacitors to an adequate analog
ground or ground plane. These capacitors should be
connected as closely as possible to the supply pins. Pins
4, 7, 14 and 17 are internally connected to V
–
(Pin 16) and
should also be tied to the same point as Pin 16 for best
shielding. Low noise linear supplies are recommended.
Switching supplies are not recommended as they will
lower the filter dynamic range.
Analog Ground (AGND):
The AGND pin is the midpoint of
a resistive voltage divider, developing a potential halfway
between the V
+
and V
–
pins, with an equivalent series
resistance nominally 7k. This serves as an internal ground
reference. Filter performance will reflect the quality of the
analog signal ground and 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 dual supply operation, the AGND pin
15622fa
4
U W
Peak BP Gain vs Nominal f
O
(V
S
=
±5V)
(Figure 3, V1 Output)
2.75
2.50
2.25
T
A
= 70°C
T
A
= 25°C
R
IN
= R
Q
Q=5
Peak BP Gain vs Nominal f
O
(V
S
=
±2.5V)
(Figure 3, V1 Output)
4.00
T
A
= 70°C
3.75
T
A
= 25°C
3.50
3.25 R
IN
= R
Q
3.00
Q=5
2.75
2.50
2.25
2.00
1.75
1.50
Q = 2.5
1.25
1.00
0.75
Q=1
0.50
0.25
0
100 120 140 160 180 200 220 240 260 280 300
NOMINAL f
O
(kHz)
1562-2 G6
BP Noise vs Nominal f
O
(V
S
=
±5V,
25°C) (Figure 3,
V1 Output) (R
IN
= R
Q
)
0
–10
–20
–30
– 40
– 50
– 60
–70
– 80
– 90
Distortion vs External Load
Resistance and Frequency
(V
S
=
±5V,
25°C) (Figure 8)
2nd ORDER LOWPASS
f
O
= 200kHz
Q = 0.7
OUTPUT LEVEL 1V
RMS
(2.83V
P-P
)
±
5V SUPPLIES
100
THD (AMPLITUDE BELOW FUNDAMENTAL) (%)
10
70
60
50
40
30
20
10
120 140 160 180 200 220 240 260 280
NOMINAL f
O
(kHz)
1562-2 G08
Q=5
Q = 2.5
Q=1
1
0.1
f
IN
= 100kHz
f
IN
= 50kHz
f
IN
= 20kHz
2k
5k
EXTERNAL LOAD RESISTANCE (Ω)
1k
0.01
–100
10k
0.001
1562-2 G09
U
U
U
LTC1562-2
PIN FUNCTIONS
should be connected to the ground plane (Figure 1). For
single supply operation, the AGND pin should be bypassed
to the ground plane with at least a 0.1µF capacitor (at least
1µF for best AC performance) (Figure 2).
ANALOG
GROUND
PLANE
1
2
3
4
V
+
0.1µF
5
6
7
8
9
10
SINGLE-POINT
SYSTEM GROUND
Figure 1. Dual Supply Ground Plane Connection
(Including Substrate Pins 4, 7, 14, 17)
3
4
V
+
0.1µF
5
6
7
8
9
10
LTC1562-2
18
17
16
15
14
13
12
11
V
+
/2
REFERENCE
RESPONSE RESPONSE
Z
IN
TYPE
AT V1
AT V2
R
BANDPASS LOWPASS
C
HIGHPASS BANDPASS
V2
R2
INV
R
Q
V1
1µF
Z
IN
+
–
V
IN
IN EACH CASE,
f
O
= (200kHz)
SINGLE-POINT
SYSTEM GROUND
DIGITAL
GROUND PLANE
(IF ANY)
1562-2 F01
Q = RQ 200kHz
R2
f
O
Figure 3. Equivalent Circuit of a Single 2nd Order Section
(Inside Dashed Line) Shown in Typical Connection. Form of
Z
IN
Determines Response Types at the Two Outputs (See Table)
Figure 2. Single Supply Ground Plane Connection
(Including Substrate Pins 4, 7, 14, 17)
15622fa
+
ANALOG
GROUND
PLANE
1
2
20
19
–
U
U
U
20
19
18
17
LTC1562-2
16
15
14
13
12
11
V
–
0.1µF
Shutdown (SHDN):
When the SHDN input goes high or is
open-circuited, the LTC1562-2 enters a “zero-power”
shutdown state and only junction leakage currents flow.
The AGND pin and the amplifier outputs (see Figure 3)
assume a high impedance state and the amplifiers effec-
tively disappear from the circuit. (If an input signal is
applied to a complete filter circuit while the LTC1562-2 is
in shutdown, some signal will normally flow to the output
through passive components around the inactive op amps.)
A small pull-up current source at the SHDN input
defaults
the LTC1562-2 to the shutdown state if the SHDN pin is left
floating.
Therefore, the user
must
connect the SHDN pin
to a logic “low” (0V for
±5V
supplies, V
–
for 5V total
supply) for normal operation of the LTC1562-2. (This
convention permits true “zero-power” shutdown since not
even the driving logic must deliver current while the part
is in shutdown.) With a single supply voltage, use V
–
for
logic “low,” do not connect SHDN to the AGND pin.
DIGITAL
GROUND PLANE
(IF ANY)
1562-2 F01
1/4 LTC1562-2
1
sR1C*
*R1 AND C ARE PRECISION
INTERNAL COMPONENTS
C
( )
(
7958Ω
R2
)
1562-2 F03
5
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