LTC1569-6_1 데이터 시트보기 (PDF) - Linear Technology
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LTC1569-6_1 Datasheet PDF : 12 Pages
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LTC1569-6
APPLICATIONS INFORMATION
Table1. fCUTOFF vs REXT, VS = 3V, TA = 25°C, Divide-by-1 Mode
REXT
Typical fCUTOFF
Typical Variation of fCUTOFF
3844Ω*
N/A
± 3.0%
5010Ω*
N/A
± 2.5%
10k
64kHz
±1%
20.18k
32kHz
± 2.0%
40.2k
16kHz
± 3.5%
*REXT values less than 10k can be used only in the divide-by-16 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 LTC1569-6 is in the divide-by-4
and divide-by-16 modes the power is automatically re-
duced. This results in up to a 40% power savings with a
single 5V supply.
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 VS, TA and REXT.
Typically this error is less than 1% (Figures 4 and 6).
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.
1.04
1.03
REXT = 5k
REXT = 10k
1.02
REXT = 20k
REXT = 40k
1.01
1.00
0.99
0.98
0.97
0.96
2
4
6
8
10
VSUPPLY (V)
1569-6 F02
Figure 2. Filter Cutoff vs VSUPPLY,
Divide-by-1 Mode, TA = 25°C
4.08
REXT = 5k
REXT = 10k
REXT = 20k
REXT = 40k
4.04
4.00
3.96
2
4
6
8
10
VSUPPLY (V)
1569-6 F04
Figure 4. Typical Divide Ratio in the
Divide-by-4 Mode, TA = 25°C
6
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)
1569-6 F03
Figure 3. Filter Cutoff vs Temperature,
Divide-by-1 Mode, REXT = 10k
1.010
1.008
1.006
1.004
1.002
1.000
0.998
0.996
0.994
0.992
0.990
–50
VS = 3V
VS = 5V
VS = 10V
–25 0 25 50
TEMPERATURE (°C)
75 100
1569-6 F05
Figure 5. Filter Cutoff vs Temperature,
Divide-by-4 Mode, REXT = 10k
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