Datasheet
5
LTC1562-2
15622fa
PIN FUNCTIONS
UUU
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.
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).
0.1µF
V
–
1562-2 F01
DIGITAL
GROUND PLANE
(IF ANY)
V
+
LTC1562-2
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 1. Dual Supply Ground Plane Connection
(Including Substrate Pins 4, 7, 14, 17)
1µF
1562-2 F01
DIGITAL
GROUND PLANE
(IF ANY)
V
+
LTC1562-2
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 LTC1562-2
1562-2 F03
C
1
sR1C*
Z
IN
Z
IN
TYPE
R
C
RESPONSE
AT V1
BANDPASS
HIGHPASS
RESPONSE
AT V2
LOWPASS
BANDPASS
7958Ω
R2
IN EACH CASE,
Q =
f
O
= (200kHz)
RQ
R2
()
200kHz
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)