LTC1569IS8-7 Linear Technology, LTC1569IS8-7 Datasheet - Page 6

• Manufacturer Part Number: LTC1569IS8-7
• Description: IC FILTER LP 10TH ORD LIN 8SOIC
• Manufacturer: Linear Technology

Specifications of LTC1569IS8-7

• Filter Type: Linear Phase, Lowpass Switched Capacitor
• Frequency - Cutoff Or Center: 300kHz
• Number Of Filters: 1
• Max-order: 10th
• Mounting Type: Surface Mount
• Package / Case: 8-SOIC (3.9mm Width)
• Lead Free Status / RoHS Status: Contains lead / RoHS non-compliant
• Voltage - Supply: -

APPLICATIONS
LTC1569-7
Self-Clocking Operation
The LTC1569-7 features a unique internal oscillator which
sets the filter cutoff frequency using a single external
resistor . The design is optimized for V
128kHz, where the filter cutoff frequency error is typically
<1% when a 0.1% external 10k resistor is used. With
different resistor values and internal divider settings, the
cutoff frequency can be accurately varied from 2kHz to
150kHz/300kHz (single 3V/5V supply). As shown in
Figure 1, the divider is controlled by the DIV/CLK (Pin 5).
Table 1 summarizes the cutoff frequency vs external
resistor values for the divide-by-1 mode.
In the divide-by-4 and divide-by-16 modes, the cutoff
frequencies in Table 1 will be lowered by 4 and 16
respectively. When the LTC1569-7 is in the divide-by-4
and divide-by-16 modes the power is automatically
6
f
CUTOFF
Figure 3. Filter Cutoff vs Temperature,
Divide-by-1 Mode, R
1.010
1.008
1.006
1.004
1.002
1.000
0.998
0.996
0.994
0.992
0.990
1
2
3
4
=
–50
128kHz (10k/R
IN
IN
GND
V
–
LTC1569-7
+
–
1, 4 OR 16
U
DIV/CLK
–25
V
V
V
S
S
S
OUT
= 3V
= 5V
= 10V
R
V
X
+
EXT
TEMPERATURE ( C)
INFORMATION
Figure 1
0
U
8
7
6
5
)
R
EXT
25
EXT
= 10k
DIVIDE-BY-16
DIVIDE-BY-4
DIVIDE-BY-1
50
W
100pF
S
75
= 3V, f
1569-7 F03
1569-7 F01
100
V
V
U
+
–
CUTOFF
=
reduced. This results in a 60% power savings with a single
5V supply.
Table1. f
R
3844
5010
10k
20.18k
40.2k
The power reduction in the divide-by-4 and divide-by-16
modes, however, effects the fundamental oscillator fre-
quency. Hence, the effective divide ratio will be slightly
different from 4:1 or 16:1 depending on V
Typically this error is less than 1% (Figures 4 and 6).
EXT
CUTOFF
1.04
1.03
1.02
1.01
1.00
0.99
0.98
0.97
0.96
4.08
4.04
4.00
3.96
Figure 4. Typical Divide Ratio in the
Divide-by-4 Mode, T
Figure 2. Filter Cutoff vs V
Divide-by-1 Mode, T
vs R
2
2
Typical f
EXT
320kHz
256kHz
128kHz
64kHz
32kHz
R
R
R
R
, V
R
R
R
R
EXT
EXT
EXT
EXT
EXT
EXT
EXT
EXT
4
CUTOFF
S
4
= 5k
= 10k
= 20k
= 40k
= 5k
= 10k
= 20k
= 40k
= 3V, T
V
V
SUPPLY
SUPPLY
6
A
A
6
A
= 25 C
= 25 C, Divide-by-1 Mode
(V)
= 25 C
(V)
Typical Variation of f
SUPPLY
8
8
1569-7 F02
1569-7 F04
S
,
, T
3.0%
2.5%
2.0%
3.5%
1%
10
10
A
and R
CUTOFF
EXT
.