DEMO MANUAL DC675B
LT1568
Fourth Order Active
RC Filter IC
Description
Demonstration circuit DC675B is for the evaluation of
filter circuits using an LT®1568. The LT1568 is a dual 2nd
order active-RC filter building block with precision ±0.75%
capacitors and low noise op amps with 180MHz GBW
trimmed to ±10% maximum variation. The ±10% GBW
variation of the LT1568 op amps allows for minimizing
the higher frequency error by decreasing resistor values.
The cutoff or center frequency (fC) range of an LT1568
filter is 200kHz to 10MHz (5MHz for a bandpass filter).
The low limit of 200kHz was chosen only to minimize
resistor noise and DC offsets (using external capacitors
the fC frequency can be less than 200kHz).
For testing and evaluation, the DC675B assembly is configured as a single 4th order, 500kHz narrow passband
bandpass filter.
For other possible LT1568 configurations, the DC675B
has unused pads for 0805 surface mount resistors and
capacitors preconfigured with PCB traces to allow for the
following high accuracy LT1568 filter circuits:
1.4th order lowpass filter
2.5th order lowpass filter
3.4th order narrow passband bandpass
4.4th order wide passband bandpass
5.4th order highpass filter
Refer to the LT1568 data sheet for additional information
about filter circuit configurations.
Design files for this circuit board are available at
http://www.linear.com/demo/DC675B
L, LT, LTC, LTM, Linear Technology and the Linear logo are registered trademarks of Linear
Technology Corporation. All other trademarks are the property of their respective owners.
Performance
Summary
range, otherwise specifications are at TA = 25°C
The l denotes specifications which apply over the full operating temperature
SYMBOL
PARAMETER
VS
Total Supply Voltage
IS
Supply Current
VS = 3V
VS = 5V
VS = ±5V
l
l
l
Output Voltage Swing High
(OUTA, OUTA, OUTB, OUTB Pins)
VS = 3V, RL = 1k
VS = 5V, RL = 1k
VS = 5V, RL = 400Ω
VS = ±5V, RL = 1k
l
l
l
l
Output Voltage Swing Low
(OUTA, OUTA, OUTB, OUTB Pins)
VS = 3V, RL = 1k
VS = 5V, RL = 1k
VS = 5V, RL = 400Ω
VS = ±5V, RL = 1k
l
l
l
l
0.05
0.07
0.20
0.12
0.15
0.40
–4.7
V
V
V
V
l
0.5
–2
µA
IB
Op Amp Input Bias Current
VCM
Common Mode Input Voltage Range
(GNDA and GNDB Pins)
CONDITIONS
MIN
l
VS = 3V
VS = ±5V
TYP
2.7
24
26
28
2.75
4.60
4.50
4.60
MAX
11
V
35
36
38
mA
mA
mA
2.85
4.80
4.65
4.75
1 to 1.9
–3.4 to 2.7
UNITS
V
V
V
V
V
V
OA Input Voltage Noise Density
f = 100kHz
1.4
nV/√Hz
OA Input Voltage Noise Density
f = 100kHz
1.0
pA/√Hz
dc675bf
1
DEMO MANUAL DC675B
LT1568 Block Diagram
4pF STRAY
CAPACITANCE
SA
INVA
3
2
V+
C1
105.7pF
4 OUTA
GNDA
6
INVB
14
15
4pF STRAY
CAPACITANCE
–
5k
SB
+
C1
105.7pF
–
13 OUTB
GNDB
11
+
5k
V–
C2
141.3pF
C2
141.3pF
–1
–1
5 OUTA
12 OUTB
DC675B BD
TYPICAL CAPACITOR SPECIFICATIONS: C1, C2 AND C2/C1 RATIO ±0.75%
SIDE A TO SIDE B CAPACITOR MISMATCH ±1%
PART TO PART CAPACITOR VARIATION ±2%
2
dc675bf
DEMO MANUAL DC675B
Quick Start Procedure
See Figure 1 for proper measurement equipment setup
and follow the procedure below.
1.Place jumpers in the following positions: JP1-DUAL
SUPPLY, JP4-AB.
2.With power off, connect a dual 5V power supply to V+
and V–.
3.Connect a 500kHz, 2VP-P, sine wave at the VINA and
GND turrets.
4.Set the scaling of an oscilloscope to 1V/1µs per division.
5.Connect an SMA to BNC coax cable from VOUTB and
–VOUTB (VOUTB bar) to oscilloscope channel 1 and 2
respectively.
6.Power up the system and the oscilloscope should show
two 2VP-P sine waves of opposite polarity (180 degrees
phase shift).
7.To test stopband attenuation set the input frequency
to 100kHz or 2MHz and the output voltage drops to
≤ 20mVP-P.
Figure 1. Quick Start Test Equipment Setup
dc675bf
3
DEMO MANUAL DC675B
Quick Start Procedure
DC675B Default Configuration
For quick testing and evaluation, the DC675B default assembly is a single 4th order, 500kHz narrow passband
bandpass filter as shown in Figure 1. This schematic was
drawn and analyzed using LTspice1 and shows the DC675B
component designators.
Re-Configuring the DC675B
Removing the default passive components (ZA1, ZA3,
R2, RA1, R3, ZAB1, R5, RB1 and R4) a variety of other
LT1568 filter circuits can be implemented. The following
figures highlight easy to design and evaluate LT1568 4th
or 5th order filter circuits using a DC675B.
Figure 2 through Figure 9 show the LTspice schematic
with simple equations to calculate the external passive
components as a function of the filter’s cutoff or center
frequency (fC) or passband gain.
There are two fC and gain error sources, the passive
component tolerance (the internal and external passive
component variation) and the GBW variation of the
LTC1568 op amps.
Specifying ≤0.5% resistors and ≤ 2% capacitors minimizes
the fc and gain error due to the external passive components
(the tolerance of an AC coupling capacitor can be 5%).
The GBW fC error depends on the filter’s gain, stopband
attenuation and the steepness of the passband to stopband
transition (filter circuits with high gain, high attenuation
and very steep transition are very sensitive to the GBW
variation). The ±10% GBW variation of the LT1568 op amps
allows for reducing the fC error at higher fC frequencies
by adjusting the calculated values by a few percent (for
example: The typical fC error of a 2MHz bandpass filter is
–2.5%. Reducing the calculated resistor values by 2.5%
will reduce the fC error due to the GBW variation). The
typical fC and gain error can be evaluated by an LTspice
frequency response simulation. Since the internal C1 and
C2 capacitors in the LT1568 model are ideal, the errors
in an LTspice simulation are due to the LT1568 op amps
and the external passive components. Using LTspice, the
following can be used as an empirical guideline for an
LT1568 at fC > 500kHz: An fC error greater than 5% or a
passband gain peak greater than 2dB is an indication that
the circuit is operating beyond a reliable fC frequency.
1 LTspice is a high performance simulator, schematic capture and waveform viewer available for
free download at www.linear.com/LTspice.
4
dc675bf
DEMO MANUAL DC675B
LTspice Simulations
LT1568 NARROW PASSBAND, 4TH ORDER BANDPASS; –3dB PASSBAND = fC /5
GAIN AT fC = GnA • GnB
ZA3 = (10 • 109/fC)/GnA; GnA 1–10
FOR GAIN AT fC > 10 INCREASE THE ZAB1 CAPACITOR;
ZAB1 = GnB • 22pF; GnB 1–10
ZAB1
22pF
.ac oct 250 50k 5Meg
ZA1
82pF
VINA
V+
+
–
ZA3
(10g/fC)
SA
R3*
(2.12g/fC)
+
–
V3
–5
.param fC = 500k
RA1 = (0.82 • 109/fC)
R3 = (2.12 • 109/fC)
ZA1 > 0.8/(ZA3 • fC)
RB1 = (0.77 • 109/fC)
R4 = (1.91 • 109/fC)
V+
INVA
RA1 (0.82g/fC)
V–
V2
5
V+
R2 IN DC675B
MUST BE 0Ω
V1
AC1
INVB
LT1568
SB
OUTA
OUTB
OUTA
OUTB
GNDA
GNDB
NC
EN
–
V–
V
R5 IN DC675B
MUST BE 0Ω
RB1 (0.77g/fC)
R4*
(1.91g/fC)
VOUTB
V–
*MINIMUM R3 AND R4 IS 100Ω.
DC675B F02a
6
0
VVOUTB
–6
INTENSITY (dB)
+
–
V+
–12
–18
–24
–30
–36
–42
–48
–54
100
1000
FREQUENCY (kHz)
DC675B F02b
Figure 2. LT1568 Fourth Order Bandpass Filter: fC = 500kHz,
–3dB BW = 100kHz (fC /5). The Default DC675B Circuit
The LTspice file for this circuit is available at www.linear.com/demo/DC675B
dc675bf
5
DEMO MANUAL DC675B
LTspice Simulations
LT1568 4TH ORDER BANDPASS USING EXTERNAL CAPACITORS
–3dB PASSBAND = √C/(10+7.7)
CN1
2.7pF
GAIN AT fC (Gn) = C2/4900
C = 70 • √Gn, C in pF
CN1 (1pF TO 10pF) CAN BE USED TO
LOWER THE CENTER FREQUENCY 0.1%-2%
ZAB1 {C}
R2 = R3 = R4 = R5 = R
R = (34 • 109)/(√10 • C + 700 • fC)
C in pF
V+
.ac oct 250 10k 1Meg
ZA1
49.9Ω
VINA
+
–
V1
AC1
+
CSA {C}
V+
R2 {R}
RA1 IN DC675B MUST BE 0Ω
R3 {R}*
V
V2
5
+
–
V3
–5
V+
INVA
–
V
+
–
ZA3 {C}
FOR fC = 100kHz:
.param R= 9.09k
.param C = 68pF
SA
LT1568
SB
OUTA
OUTB
OUTA
OUTB
GNDA
GNDB
NC
EN
–
V–
V
R5 {R}
INVB
RB1 IN DC675B MUST BE 0Ω
R4 {R}*
CSB {C}
VOUTB
V–
*MINIMUM R3 AND R4 IS 100Ω.
DC675B F03a
6
0
VVOUTB
–6
INTENSITY (dB)
–12
–18
–24
–30
–36
–42
–48
–54
–60
10
100
FREQUENCY (kHz)
1000
DC675B F03b
Figure 3. LT1568 Fourth Order Bandpass Filter (Using External
Capacitors for Center Frequencies Less Than 200kHz)
The LTspice file for this circuit is available at www.linear.com/demo/DC675B
6
dc675bf
DEMO MANUAL DC675B
LTspice Simulations
LT1568 WIDE PASSBAND 4TH ORDER BANDPASS
–3dB PASSBAND fCHP TO fCLP (fCLP ≥ 3 • fCHP)
fCHP ≤ 50kHz, < fCLP AND fCLP ≤ 10MHz
PASSBAND GAIN AT √(fCHP • fCLP) = 0dB
ZAB1
100pF
.param fCHP = 50k
.param fCLP = 2M
.ac oct 250 1k 50Meg
ZA1
0.1µF
VINA
*R3 (1.24g/fCLP)
+
–
V3
–5
V+
INVA
RA1 ON DC675B MUST BE 0Ω
V–
V2
5
V+
R2
(1.21g/fCLP)
V1
AC1
V+
+
–
ZA3
(1.18g/fCLP)
ZA3 = (1.18 • 109/fCLP)
R2 = (1.21 • 109/fCLP)
R3 = (1.24 • 109/fCLP)
RB1 = (1.6 • 109/fcHP)
R4 = (0.78 • 109/fcHP)
SA
INVB
LT1568
SB
OUTA
OUTB
OUTA
OUTB
GNDA
GNDB
NC
EN
–
V–
V
R5 IN DC675B
MUST BE 0Ω
RB1 (1.6g/fCHP)
R4*
(0.78g/fCHP)
VOUTB
V–
*MINIMUM R3 AND R4 IS 100Ω.
DC675B F04a
6
0
VVOUTB
–6
INTENSITY (dB)
+
–
V+
–12
–18
–24
–30
–36
–42
–48
–54
1
10
100
1M
FREQUENCY (kHz)
10M
DC675B F04b
Figure 4. LT1568 Fourth Order Wide Passband Bandpass Filter
The LTspice file for this circuit is available at www.linear.com/demo/DC675B
dc675bf
7
DEMO MANUAL DC675B
LTspice Simulations
ZAB1
(1.82g/fC)
LT1568 4th ORDER BUTTERWORTH LOWPASS FILTER
V+
.ac oct 250 10k 10Meg
ZA3
(1.05g/fC)
VINA
+
–
+
–
*R3 (1.05g/fC)
V–
V2
5
+
–
V3
–5
V+
INVA
RA1 ON DC675B MUST BE 0Ω
V1
AC1
V+
V+
R2
(1.58g/fC)
.param fC = 1Meg
PASSBAND GAIN = 0dB
ZA3 = R3 = (1.05 • 109/fC)
R2 = (1.58 • 109/fC)
SA
R5
(0.88/fC)
INVB
LT1568
SB
OUTA
OUTB
OUTA
OUTB
GNDA
GNDB
NC
EN
V–
V–
RB1 IN DC675B MUST BE 0Ω
R4*
(1.82g/fC)
VOUTB
V–
ZAB1 = R4 = (1.82 • 109/fC)
R5 = (0.88 • 109/fC)
DC675B F05a
NOTE: ANY IMPEDANCE IN SERIES OR PARALLEL
WITH AN INPUT RESISTOR CHANGES THE
FILTER’S POLES AND PASSBAND GAIN.
*MINIMUM R3 AND R4 IS 100Ω.
10
0
VVOUTB
INTENSITY (dB)
–10
–20
–30
–40
–50
–60
–70
–80
10
100
1M
FREQUENCY (kHz)
10M
DC675B F05b
Figure 5. LT1568 Fourth Order Bandpass Lowpass Filter
The LTspice file for this circuit is available at www.linear.com/demo/DC675B
8
dc675bf
DEMO MANUAL DC675B
LTspice Simulations
ZAB1
(0.88g/fC)
LT1568 4th ORDER BUTTERWORTH LOWPASS FILTER
(LINEAR PASSBAND PHASE)
V+
.ac oct 250 10k 10Meg
ZA3
(0.72g/fC)
VINA
V+
+
–
*R3 (0.72g/fC)
V–
V2
5
+
–
V3
–5
V+
INVA
RA1 ON DC675B MUST BE 0Ω
V1
AC1
.param fc = 1Meg
PASSBAND GAIN = 0dB
ZA3 = R3 = (0.72 • 109/fC)
R2 = (1.14 • 109/fC)
SA
R5
(0.72/fC)
INVB
LT1568
SB
OUTA
OUTB
OUTA
OUTB
GNDA
GNDB
NC
EN
–
V–
V
RB1 IN DC675B MUST BE 0Ω
R4*
(0.88g/fC)
VOUTB
V–
ZAB1 = R4 = (0.88 • 109/fC)
R5 = (0.72 • 109/fC)
DC675B F06a
NOTE: ANY IMPEDANCE IN SERIES OR PARALLEL
WITH AN INPUT RESISTOR CHANGES THE
FILTER’S POLES AND PASSBAND GAIN.
*MINIMUM R3 AND R4 IS 100Ω.
10
0
VVOUTB
–10
INTENSITY (dB)
+
–
V+
R2
(1.14g/fC)
–20
–30
–40
–50
–60
–70
–80
10
100
1M
FREQUENCY (kHz)
10M
DC675B F06b
Figure 6. LT1568 Fourth Order Bessel Lowpass Filter (Linear Passband Phase)
The LTspice file for this circuit is available at www.linear.com/demo/DC675B
dc675bf
9
DEMO MANUAL DC675B
LTspice Simulations
LT1568 4th ORDER ELLIPTIC LOWPASS FILTER
PASSBAND ±0.3dB
STOPBAND ATTENUATION = –42dB AT 2.3 • fC
CN1
12pF
RN1
(1.9g/fC)
V+
.ac oct 250 10k 10Meg
ZA3
(1.24g/fC)
VINA
+
–
+
–
*R3 (1.24g/fC)
V–
V2
5
+
–
V3
–5
.param fc = 1Meg
PASSBAND GAIN = 0dB
ZA3 = R3 = (1.24 • 109/fC)
R2 = (1.66 • 109/fC)
RN1 = (1.9 • 109/fC)
R4 = (1.9 • 109/fC)
R5 = (0.64 • 109/fC)
V+
INVA
RA1 ON DC675B MUST BE 0Ω
V1
AC1
V+
V+
R2
(1.66g/fC)
SA
R5
(0.64g/fC)
INVB
LT1568
SB
OUTA
OUTB
OUTA
OUTB
GNDA
GNDB
NC
EN
V–
V–
RB1 IN DC675B MUST BE 0Ω
R4*
(1.9g/fC)
VOUTB
V–
NOTE: ANY IMPEDANCE IN SERIES OR PARALLEL
WITH AN INPUT RESISTOR CHANGES THE
FILTER’S POLES AND PASSBAND GAIN.
*MINIMUM R3 AND R4 IS 100Ω.
DC675B F07a
6
0
VVOUTB
–6
INTENSITY (dB)
–12
–18
–24
–30
–36
–42
–48
–54
–60
–66
10
100
1M
FREQUENCY (kHz)
10M
DC675B F07b
Figure 7. LT1568 Fourth Order Elliptic Lowpass Filter
The LTspice file for this circuit is available at www.linear.com/demo/DC675B
10
dc675bf
DEMO MANUAL DC675B
LTspice Simulations
ZAB1
(2g/fC)
LT1568 5th ORDER BUTTERWORTH LOWPASS FILTER
.ac oct 250 10k 10Meg
ZA1
(0.63g/fC)
VINA
V1
AC1
V+
+
–
ZA3
(0.63g/fC)
V+
R2
(0.77g/fC)
*R3 (1.26g/fC)
V–
V2
5
+
–
V3
–5
.param fc = 1Meg
PASSBAND GAIN = 0dB
ZA1 = ZA3 = (0.63 • 109/fC)
R3 = (1.26 • 109/fC)
R2 = (0.75 • 109/fC)
ZAB1 = R4 = (2 • 109/fC)
R5 = (0.73 • 109/fC)
V+
INVA
RA1 ON DC675B MUST BE 0Ω
ZA2
1nF
INVB
LT1568
SA
SB
OUTA
OUTB
OUTA
OUTB
GNDA
GNDB
NC
EN
–
V–
V
R5
(0.73g/fC)
RB1 IN DC675B MUST BE 0Ω
R4*
(2g/fC)
VOUTB
V–
NOTE: ANY IMPEDANCE IN SERIES OR PARALLEL
WITH AN INPUT RESISTOR CHANGES THE
FILTER’S POLES AND PASSBAND GAIN.
*MINIMUM R3 AND R4 IS 100Ω.
DC675B F08a
10
0
VVOUTB
–10
–20
INTENSITY (dB)
+
–
V+
–30
–40
–50
–60
–70
–80
–90
–100
10
100
1M
FREQUENCY (kHz)
10M
DC675B F08b
Figure 8. LT1568 Fourth Order Butterworth Lowpass Filter
The LTspice file for this circuit is available at www.linear.com/demo/DC675B
dc675bf
11
DEMO MANUAL DC675B
LTspice Simulations
ZAB1
(0.6g/fC)
LT1568 5th ORDER BESSEL LOWPASS FILTER
(LINEAR PASSBAND PHASE)
V+
.ac oct 250 10k 10Meg
ZA1
(0.4g/fC)
VINA
+
–
V1
AC1
V+
+
–
ZA3
(0.4g/fC)
V+
R2
(0.4g/fC)
INVA
RA1 ON DC675B MUST BE 0Ω
ZA2
1nF
*R3 (0.8g/fC)
V–
V2
5
+
–
V3
–5
.param fC = 1Meg
PASSBAND GAIN = 0dB
ZA1 = ZA3 = (0.4 • 109/fC)
R3 = (0.8 • 109/fC)
R2 = (0.4 • 109/fC)
ZAB1 = R4 = (0.6 • 109/fC)
R5 = (0.7 • 109/fC)
V+
INVB
LT1568
SA
R5
(0.7g/fC)
SB
OUTA
OUTB
OUTA
OUTB
GNDA
GNDB
NC
EN
V–
V–
RB1 IN DC675B MUST BE 0Ω
R4*
(0.6g/fC)
VOUTB
V–
NOTE: ANY IMPEDANCE IN SERIES OR PARALLEL
WITH AN INPUT RESISTOR CHANGES THE
FILTER’S POLES AND PASSBAND GAIN.
*MINIMUM R3 AND R4 IS 100Ω.
DC675B F09a
10
0
VVOUTB
INTENSITY (dB)
–10
–20
–30
–40
–50
–60
–70
–80
10
1M
100
FREQUENCY (kHz)
10M
DC675B F09b
Figure 9. LT1568 Fifth Order Bessel Lowpass Filter (Linear Passband Phase)
The LTspice file for this circuit is available at www.linear.com/demo/DC675B
12
dc675bf
DEMO MANUAL DC675B
LTspice Simulations
ZAB1
100pF
LT1568 4th ORDER HIGHPASS FILTER
V+
.ac oct 250 10k 10Meg
ZA1
75
VINA
V1
AC1
V+
+
–
V+
R2 ON DC675B MUST BE 0Ω
fIN ≤ 10MHz
RA1 (1.76g/fC)
V–
V2
5
+
–
V3
–5
V+
INVA
.param fC = 100k
PASSBAND GAIN = ZA3/100pF
RA1 = (1.76 • 109/fC)
R3 = (0.66 • 109/fC)
R5 IN DC675B MUST BE 0Ω
SB
OUTA
OUTB
OUTA
OUTB
GNDA
GNDB
NC
EN
–
V–
V
ZA1 = 1/(6.28 • ZA2 • 20MHz)
INVB
LT1568
SA
*R3 (0.66g/fC)
RB1 (1.76g/fC)
R4*
(1.42g/fC)
VOUTB
V–
RB1 = (1.76 • 109/fC)
R4 = (1.42 • 109/fC)
*MINIMUM R3 AND R4 IS 100Ω.
DC675B F10a
6
0
VVOUTB
–6
INTENSITY (dB)
+
–
ZA3
100pF
–12
–18
–24
–30
–36
–42
–48
10
100
1M
FREQUENCY (kHz)
10M
DC675B F10b
Figure 10. LT1568 Fourth Order Highpass Filter
The LTspice file for this circuit is available at www.linear.com/demo/DC675B
dc675bf
13
DEMO MANUAL DC675B
LTspice Simulations
SPECIAL FUNCTION LT1568 FILTER
A SQUAREWAVE TO DIFFERENTIAL SINEWAVE CONVERTER
fC RANGE: 50kHz TO 5MHz
CN1
27pF
.param fC = 1Meg
.tran 0 25u 20u
ZA3
68pF
ZA1*
(6.2g/fC)
VINA
+
–
V+
V1
AC1
V
+
–
R3 (1g/fC)
V2
5
CD3
0.1µF
* NOTE: THE RATIO ZA1/ZA2 SETS THE VP-P
OF THE DIFERENTIAL OUTPUT (O1-O2).
FOR V+ = 5V AND A
5V INPUT SQUAREWAVE:
FOR V+ = 3V AND A
3V INPUT SQUAREWAVE:
ZA1/ZA2
VP-P
ZA1/ZA2
VP-P
1
2
4.75
6.2
12.4
8
5
2.5
2
1
0.95
2
3.4
7.5
5
3
2
1
V+
INVA
RA1 IN DC675B MUST BE 0Ω
ZA2
(1g/fC)
+
V+
R2 (1g/fC)
SA
ZAB1
(1g/fC)
INVB
LT1568
R5 IN DC675B MUST BE 0Ω
SB
RB1 (1g/fC)
R4 (1g/fC)
OUTA
OUTB
OUTA
OUTB
O1
GNDA
GNDB
O2
NC
EN
V–
V–
DC675B F11a
5.5
5.0
VVINA
4.5
Y-AXIS TITLE? (Y)
4.0
3.5
VOUT1
3.0
2.5
2.0
VOUT2
1.5
1.0
0.5
0
–0.5
0
0.5
1
1.5
2
2.5
3
X-AXIS TITLE? (µs)
3.5
4
4.5
5
DC675B F11b
Figure 11
The LTspice file for this circuit is available at www.linear.com/demo/DC675B
14
dc675bf
Information furnished by Linear Technology Corporation is believed to be accurate and reliable.
However, no responsibility is assumed for its use. Linear Technology Corporation makes no representation that the interconnection of its circuits as described herein will not infringe on existing patent rights.
A
B
C
D
TP2
TP1
J2
J1
TP5
TP10
V-
CD5
10uF
1206
CD4
10uF
1206
3
RA3
RA2
CD7
1uF
1206
CD6
1uF
1206
49.9
49.9
ZA1
82pF+/-5%
D1
BAT54S
5
1. ALL CAPACITORS AND RESISTORS ARE 0805
NOTES: UNLESS OTHERWISE SPECIFIED,
VOUTA
VOUTA
GND
VINA
VTP3
-2.7V to -6V
GND
V+
2.7V to 6V
V+
2
1
5
1.65K,0.1%
3
4
2
1
DUAL SUPPLY
JP1
0
V-
V-
NC
GNDA
OUTA
OUTA
SA
U1
V+
OPT
9
10
11
12
13
14
15
16
RN1
B
JP4
3
GNDB
1
AB
2
R4
3
THIS CIRCUIT IS PROPRIETARY TO LINEAR TECHNOLOGY AND
SUPPLIED FOR USE WITH LINEAR TECHNOLOGY PARTS.
0
R6
OPT
0603
R1
5.11K
0603
CD8
0.1uF
0603
3.83K,0.1%
1.54K,0.1%
RB1
R5
CSB
OPT
SCALE = NONE
PHILIP K.
A.K.
APPROVALS
OPT
ZAB1 22pF+/-5%
CN1
RFF1 OPT
V-
V-
EN
GNDB
OUTB
OUTB
SB
INVB
LT1568CGN
INVA
V+
CUSTOMER NOTICE
CD2
0.1uF
0603
8
7
6
5
4
3
2
1
V+ CD1
0.1uF 0603
3
LINEAR TECHNOLOGY HAS MADE A BEST EFFORT TO DESIGN A
CIRCUIT THAT MEETS CUSTOMER-SUPPLIED SPECIFICATIONS;
HOWEVER, IT REMAINS THE CUSTOMER'S RESPONSIBILITY TO PCB DES.
VERIFY PROPER AND RELIABLE OPERATION IN THE ACTUAL
APPLICATION. COMPONENT SUBSTITUTION AND PRINTED
APP ENG.
CIRCUIT BOARD LAYOUT MAY SIGNIFICANTLY AFFECT CIRCUIT
PERFORMANCE OR RELIABILITY. CONTACT LINEAR
TECHNOLOGY APPLICATIONS ENGINEERING FOR ASSISTANCE.
CD3
0.1uF
0603
4.22K,0.1%
VCC
TP4
TP6
R3
RA1
R2
CSA
OPT
SINGLE SUPPLY
GND
GNDA
ZA3
20K
ZA4
OPT
ZA2
OPT
V+
4
ZB2
OPT
__
2
DATE:
N/A
SIZE
DESCRIPTION
RB3
49.9
GND
VINB
J4
J3
VOUTB
DEMO CIRCUIT 675B
Wednesday, January 21, 2015
1
SHEET 1
ACTIVE RC FILTER BUILDING BLOCK
LT1568CGN
IC NO.
DATE
01-21-15
VOUTB
PHILIP K.
APPROVED
2
OF 1
REV.
1630 McCarthy Blvd.
Milpitas, CA 95035
Phone: (408)432-1900 www.linear.com
Fax: (408)434-0507
LTC Confidential-For Customer Use Only
49.9
RB2
TP8
TP11
PRODUCTION
1
REVISION HISTORY
TECHNOLOGY
SHDN
GND
TITLE: SCHEMATIC
TP7
TP9
ZB1
OPT
ZB4
OPT
2
REV
GNDB
V+
ECO
TP12
ZB3
OPT
2
A
B
C
D
DEMO MANUAL DC675B
Schematic Diagram
dc675bf
15
DEMO MANUAL DC675B
DEMONSTRATION BOARD IMPORTANT NOTICE
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This demonstration board (DEMO BOARD) kit being sold or provided by Linear Technology is intended for use for ENGINEERING DEVELOPMENT
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If this evaluation kit does not meet the specifications recited in the DEMO BOARD manual the kit may be returned within 30 days from the date
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arising from the handling or use of the goods. Due to the open construction of the product, it is the user’s responsibility to take any and all
appropriate precautions with regard to electrostatic discharge. Also be aware that the products herein may not be regulatory compliant or
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Mailing Address:
Linear Technology
1630 McCarthy Blvd.
Milpitas, CA 95035
Copyright © 2004, Linear Technology Corporation
16 Linear Technology Corporation
dc675bf
LT 0415 • PRINTED IN USA
1630 McCarthy Blvd., Milpitas, CA 95035-7417
(408) 432-1900
●
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LINEAR TECHNOLOGY CORPORATION 2015