LTC1065 Linear Technology, LTC1065 Datasheet - Page 6

• Manufacturer Part Number: LTC1065
• Description: DC Accurate/ Clock-Tunable Linear Phase 5th Order Bessel Lowpass Filter
• Manufacturer: Linear Technology

PI FU CTIO S
TYPICAL PERFOR
LTC1065
Power Supply Pins (Pins 6, 3, N Package)
The positive and negative supply pin should be bypassed
with a high quality 0.1 F ceramic capacitor. In applications
where the clock pin (5) is externally swept to provide
several cutoff frequencies, the output DC offset variation
is minimized by connecting an additional 1 F solid tanta-
lum capacitor in parallel with the 0.1 F disc ceramic. This
technique was used to generate the graphs of the output
DC offset variation versus clock; they are illustrated in the
Typical Performance Characteristics section.
When the power supply voltage exceeds 7V, and when
V
ground) connect a signal diode between the positive
supply pin and ground to prevent latch-up (see Typical
Applications).
Ground Pin (Pin 2, N Package)
The ground pin merges the internal analog and digital
ground paths. The potential of the ground pin is the
reference for the internal switched-capacitor resistors,
and the reference for the external clock. The positive input
of the internal op amp is also tied to the ground pin.
For dual supply operation, the ground pin should be
connected to a high quality AC and DC ground. A ground
plane, if possible, should be used. A poor ground will
6
–
U
is applied before V
U
HORIZONTAL: 0.1ms/DIV, VERTICAL: 2V/DIV
V
SQUARE WAVE
Transient Response
S
= 5V, f
C
U
= 10kHz, V
+
(if V
IN
W
= 1kHz 3V
+
A
is allowed to go below
U
CE
P
C
HARA TERISTICS
1065 G16
C
degrade DC offset and it will increase clock feedthrough,
noise and distortion.
A small amount of AC current flows out of the ground pin
whether or not the internal oscillator is used. The fre-
quency of the ground current equals the frequency of the
clock. The average value of this current is approximately
55 A, 110 A, 170 A for 2.5V, 5V and 7.5V supplies
respectively.
For single supply operation, the ground pin should be
preferably biased at half supply (see Typical Applications).
V
The V
of output DC offset voltage or to introduce a desired output
DC level. The DC gain from the V
output pin equals two.
Any DC voltage applied to this pin will reflect at the output
pin of the filter multiplied by two.
If the V
ground pin. The DC bias current flowing into the V
pin is typically 10pA.
The V
ground; AC signals applied to this pin will degrade the filter
response.
OS
Adjust Pin (Pin 8, N Package)
OS
OS
OS
adjust pin can be used to trim any small amount
adjust pin should always be connected to an AC
adjust pin is not used, it should be shorted to the
45
40
35
30
25
20
15
10
5
0
0
Group Delay
V
f
C
S
= 10kHz
= ±5V
3
INPUT FREQUENCY (kHz)
6
9
12
OS
15
adjust pin to the filter
18
1065 G17
21
OS
adjust