LTC1562 Linear Technology, LTC1562 Datasheet - Page 5

• Manufacturer Part Number: LTC1562
• Description: Very Low Noise/ Low Distortion Active RC Quad Universal Filter
• Manufacturer: Linear Technology

(Figure 1). For single supply operation, the AGND pin
should be bypassed to the ground plane with at least a
0.1 F capacitor (at least 1 F for best AC performance)
(Figure 2).
PIN
U
FUNCTIONS
ANALOG
GROUND
PLANE
ANALOG
GROUND
PLANE
V
V
Figure 2. Single Supply Ground Plane Connection
(Including Substrate Pins 4, 7, 14, 17)
0.1 F
0.1 F
Figure 1. Dual Supply Ground Plane Connection
(Including Substrate Pins 4, 7, 14, 17)
+
+
SINGLE-POINT
SYSTEM GROUND
SINGLE-POINT
SYSTEM GROUND
U
10
10
1
2
3
4
5
6
7
8
9
1
2
3
4
5
6
7
8
9
U
LTC1562
LTC1562
GROUND PLANE
GROUND PLANE
20
19
18
17
16
15
14
13
12
11
20
19
18
17
16
15
14
13
12
11
DIGITAL
(IF ANY)
DIGITAL
(IF ANY)
REFERENCE
V
V
+
/2
–
0.1 F
1 F
1562 F01
1562 F01
Shutdown (SHDN): When the SHDN input goes high or is
open-circuited, the LTC1562 enters a “zero-power” shut-
down 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 effectively
disappear from the circuit. (If an input signal is applied to
a complete filter circuit while the LTC1562 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 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
supply) for normal operation of the LTC1562. (This con-
vention 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
logic “low”— do not connect SHDN to the AGND pin.
Figure 3. Equivalent Circuit of a Single 2nd Order Section
(Inside Dashed Line) Shown in Typical Connection. Form of Z
Determines Response Types at the Two Outputs (See Table)
1/4 LTC1562
V2
Z
IN
TYPE
R
C
R2
BANDPASS
RESPONSE
HIGHPASS
AT V1
sR1C*
1
RESPONSE
BANDPASS
LOWPASS
AT V2
Z
+
–
IN
*R1 AND C ARE PRECISION
INV
V
INTERNAL COMPONENTS
IN
–
+
IN EACH CASE,
f
Q =
R
O
Q
LTC1562
= (100kHz)
C
RQ
–
R2
for 5V total
100kHz
f
O
10k
1562 F01
V1
R2
–
5
for
IN