LT1568CGN#PBF Linear Technology, LT1568CGN#PBF Datasheet - Page 10

• Manufacturer Part Number: LT1568CGN#PBF
• Description: IC FILTER BUILDING BLOCK 16SSOP
• Manufacturer: Linear Technology

Specifications of LT1568CGN#PBF

• Filter Type: Bandpass
• Frequency - Cutoff Or Center: 200kHz
• Number Of Filters: 2
• Max-order: 2nd
• Voltage - Supply: 2.7 V ~ 11 V, ±2.7 V ~ 5.5 V
• Mounting Type: Surface Mount
• Package / Case: 16-SSOP
• Lead Free Status / RoHS Status: Lead free / RoHS Compliant

APPLICATIO S I FOR ATIO
LT1568
The LT1568 has been designed to make the implementa-
tion of high frequency filtering functions very easy. Inter-
nal low noise amplifiers and capacitors are configured in
a topology that requires only three external resistors to
implement a 2nd order filter stage. The two 2nd order
stages can be used independently or cascaded for simple
4th order filter functions. With two stages integrated on
the same die, the matching of the independent sections is
better than what can be achieved with separate amplifier
components.
OPERATING WITH SINGLE OR DUAL SUPPLIES
Figure 1 shows the recommended connection of an analog
ground plane with the LT1568 biased from either symmetri-
cal dual ( V) power supplies or a single supply. Connec-
tion of the two GND pins is important to properly DC bias
the internal amplifiers. The use of a ground plane helps to
minimize noise and stray components to preserve signal
integrity and maintain frequency response accuracy.
When biasing from a dual supply, it is recommended that
a Schottky diode clamp (BAT54S) be added as shown.
These diodes ensure that improper supply voltages,
through either reverse polarity or power-up sequencing,
do not damage the LT1568.
10
ANALOG
GROUND
PLANE
0.1 F
Dual Supply Power and Ground Connections
V
–
SINGLE POINT
SYSTEM GROUND
BAT54S
U
1
2
3
4
5
6
7
8
V
INVA
SA
OUTA
OUTA
GNDA
NC
V
+
–
U
LT1568
GNDB
OUTB
OUTB
INVB
DIGITAL GROUND PLANE
Figure 1. Dual and Single Supply and Ground Plane Connections
SB
EN
V
V
+
–
16
15
14
13
12
11
10
9
W
(IF ANY)
0.1 F
1568 F01a
V
+
U
SIMPLE FILTER IMPLEMENTATIONS
The basic 2nd order filter block of the LT1568, with three
external resistors connected as shown in the Block Dia-
gram, has the following lowpass transfer function:
where e
and
The typical values of the internal capacitors are:
These filter functions assume ideal amplifiers.
C1= 105.7pF
C2 = 141.3pF
DC
Q
e
e
OUT
IN
GAIN
C
OUT
ANALOG
GROUND
PLANE
0.1 F
Single Supply Power and Ground Connections
1
•
SINGLE POINT
SYSTEM GROUND
–
is either OUTA or OUTB,
R
s
R
R
1
2
2
2
1
•
DC
,
R
•
2
f
GAIN
O
2
C C
Q
1
f
1
2
3
4
5
6
7
8
O
•
R
2
• 2
s
V
INVA
SA
OUTA
OUTA
GNDA
NC
V
3
+
–
2
LT1568
•
R
R R
2
f
R
GNDB
O
OUTB
OUTB
1
2
INVB
DIGITAL GROUND PLANE
2
f
•
SB
EN
V
V
O
2
•
•
+
–
R
1
R
2
2
16
15
14
13
12
11
10
3
9
3
(IF ANY)
•
•
R
C C
–
3
1
C
•
•
2
f
0.1 F
O
•
2
1568 F01b
R R
V
+
1
•
2
1568f