Datasheet
5
LTC1562
1562fa
PIN FUNCTIONS
UUU
package does not have the four substrate pins (Pins 4, 7,
14, 17 in the 20-pin package).
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
–
for 5V total
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
–
for
logic “low”—do not connect SHDN to the AGND pin.
(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). These figures show 20-pin package connec-
tions. The same principles apply to the 16-pin package
with allowance for its different pin numbers. The 16-pin
Figure 1. Dual Supply Ground Plane Connection
(Including Substrate Pins 4, 7, 14, 17)
0.1µF
V
–
1562 F01
DIGITAL
GROUND PLANE
(IF ANY)
V
+
LTC1562
20-PIN SSOP
0.1µF
ANALOG
GROUND
PLANE
20
19
18
17
16
15
14
13
12
11
1
2
3
4
5
6
7
8
9
10
SINGLE-POINT
SYSTEM GROUND
1µF
1562 F01
DIGITAL
GROUND PLANE
(IF ANY)
V
+
LTC1562
20-PIN SSOP
V
+
/2
REFERENCE
0.1µF
ANALOG
GROUND
PLANE
20
19
18
17
16
15
14
13
12
11
1
2
3
4
5
6
7
8
9
10
SINGLE-POINT
SYSTEM GROUND
Figure 2. Single Supply Ground Plane Connection
(Including Substrate Pins 4, 7, 14, 17)
–
+
+
–
R2
R
Q
V
IN
INV
*R1 AND C ARE PRECISION
INTERNAL COMPONENTS
V2 V1
1/4 LTC1562
1562 F01
C
1
sR1C*
Z
IN
Z
IN
TYPE
R
C
RESPONSE
AT V1
BANDPASS
HIGHPASS
RESPONSE
AT V2
LOWPASS
BANDPASS
10kΩ
R2
IN EACH CASE,
Q =
f
O
= (100kHz)
RQ
R2
()
100kHz
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)