LTC1569CS8-7 View Datasheet(PDF) - Linear Technology
Part Name
Description
Manufacturer
LTC1569CS8-7 Datasheet PDF : 12 Pages
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LTC1569-7
APPLICATIONS INFORMATION
1.010
1.008
1.006
1.004
VS = 3V
VS = 5V
VS = 10V
1.002
1.000
0.998
0.996
0.994
0.992
0.990
–50 –25 0
25 50 75 100
TEMPERATURE (°C)
1569-7 F05
Figure 5. Filter Cutoff vs Temperature,
Divide-by-4 Mode, REXT = 10k
16.32
16.16
REXT = 5k
REXT = 10k
REXT = 20k
REXT = 40k
16.00
15.84
2
4
6
8
10
VSUPPLY (V)
1569-7 F06
Figure 6. Typical Divide Ratio in the
Divide-by-16 Mode, TA = 25°C
1.010
1.008
1.006
1.004
VS = 3V
VS = 5V
VS = 10V
1.002
1.000
0.998
0.996
0.994
0.992
0.990
–50 –25 0
25 50 75 100
TEMPERATURE (°C)
1569-7 F07
Figure 7. Filter Cutoff vs Temperature,
Divide-by-16 Mode, REXT = 10k
The cutoff frequency is easily estimated from the equation
in Figure 1. Examples 1 and 2 illustrate how to use the
graphs in Figures 2 through 7 to get a more precise
estimate of the cutoff frequency.
Example 1: LTC1569-7, REXT = 20k, VS = 3V, divide-by-16
mode, DIV/CLK (Pin␣ 5) connected to V + (Pin 7), TA = 25°C.
Using the equation in Figure 1, the approximate filter
cutoff frequency is fCUTOFF = 128kHz • (10k/20k)
• (1/16) = 4kHz.
For a more precise fCUTOFF estimate, use Table 1 to get
a value of fCUTOFF when REXT = 20k and use the graph
in Figure 6 to find the correct divide ratio when VS = 3V
and REXT = 20k. Based on Table 1 and Figure 6, fCUTOFF
= 64kHz • (20.18k/20k) • (1/16.02) = 4.03kHz.
From Table 1, the part-to-part variation of fCUTOFF will
be ±2%. From the graph in Figure 7, the 0°C to 70°C
drift of fCUTOFF will be – 0.2% to 0.2%.
Example 2: LTC1569-7, REXT = 5k, VS = 5V, divide-by-1
mode, DIV/CLK (Pin␣ 5) connected to V – (Pin 4), TA = 25°C.
Using the equation in Figure 1, the approximate filter
cutoff frequency is fCUTOFF = 128kHz • (10k/5k)
• (1/1) = 256kHz.
For a more precise fCUTOFF estimate, use Table 1 to get
fCUTOFF frequency for REXT = 5k and use Figure 2 to
correct for the supply voltage when VS = 5V. From
Table␣ 1 and Figure 2, fCUTOFF = 256k • (5.01k/5k) •
0.970 = 249kHz.
7
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