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
16.32
16.16
REXT = 5k
REXT = 10k
REXT = 20k
REXT = 40k
16.00
15.84
2
4
6
8
10
VSUPPLY (V)
1569-6 F06
Figure 6. Typical Divide Ratio in the
Divide-by-16 Mode, TA = 25°C
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 F07
Figure 7. Filter Cutoff vs Temperature,
Divide-by-16 Mode, REXT = 10k
Example 1: LTC1569-6, 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 = 64kHz • (10k/20k)
• (1/16) = 2kHz.
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
= 32kHz • (20.18k/20k) • (1/16.02) = 2.01kHz.
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: LTC1569-6, REXT = 10k, 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 = 64kHz • (10k/10k)
• (1/1) = 64kHz.
For a more precise fCUTOFF estimate, use Figure 2 to
correct for the supply voltage when VS = 5V. From
Table␣ 1 and Figure 2, fCUTOFF = 64k • (10k/10k) • 0.970
= 62.1kHz.
The oscillator is sensitive to transients on the positive
supply. The IC should be soldered to the PC board and the
PCB layout should include a 1µF ceramic capacitor be-
tween V + (Pin 7) and V – (Pin 4) , as close as possible to
the IC to minimize inductance. Avoid parasitic capacitance
on RX and avoid routing noisy signals near RX (Pin 6). Use
a ground plane connected to V – (Pin 4) for single supply
applications. Connect a ground plane to GND (Pin 3) for
dual supply applications and connect V – (Pin 4) to a
copper trace with low thermal resistance.
Input and Output Voltage Range
The input signal range includes the full power supply
range. For a single 3V supply, the output voltage swing is
typciallly 2.1VP-P and at least 1.9VP-P over the commercial
temperature range. For single 5V and ±5V supplies, the
output swing depends on clock frequency and divider
setting.
For REXT = 10k, divide-by-1 mode (fCUTOFF = 64kHz) and
VS = 5V, the output swing is typically 3.6VP-P
(3.2VP-P 0°C to 70°C). For REXT = 10k, divide-by-4 or
divide-by-16 modes (fCUTOFF = 16kHz or 4kHz) and
VS = 5V, the output swing is typically limited to
VMIN = V – + 80mV and VMAX = V + – 1V or 3.92VP-P.
For REXT = 10k, divide-by-1 mode and VS = ±5V, the output
voltage is typically 5VP-P (4.3VP-P 0°C to 70°C). For
REXT = 10k, divide-by-4 mode (fCUTOFF = 16kHz) and
VS = ±5V, the output voltage range is typically 6.3VP-P
(5.8VP-P 0°C to 70°C). For REXT = 10k, divide-by-16 mode
(fCUTOFF = 4kHz) and VS = ±5V, the output voltage is
typically 8.5VP-P (7.5VP-P 0°C to 70°C). In each case, the
output voltage range increases as REXT is increased until
7
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