Datasheet LTC6905 (Analog Devices) - 9
| Fabricante | Analog Devices |
| Descripción | 17MHz to 170MHz Resistor Set SOT-23 Oscillator |
| Páginas / Página | 12 / 9 — APPLICATIONS INFORMATION. JITTER AND DIVIDE RATIO. JITTER AND STRAY … |
| Formato / tamaño de archivo | PDF / 175 Kb |
| Idioma del documento | Inglés |
APPLICATIONS INFORMATION. JITTER AND DIVIDE RATIO. JITTER AND STRAY CAPACITANCE ON THE SET PIN. (PIN 3)
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Versión de texto del documento
LTC6905
APPLICATIONS INFORMATION JITTER AND DIVIDE RATIO
1) The bypass capacitor must be placed as close as possible At a given output frequency, a higher master oscillator to the LTC6905, and no vias should be placed between frequency and a higher divide ratio will result in lower the capacitor and the LTC6905. The bypass capacitor jitter and higher power supply dissipation. Indeterminate must be on the same side of the circuit board as the jitter percentage will decrease by a factor of slightly less LTC6905. than the square root of the divider ratio, while determinate 2) The resistor RSET should be placed as close as possible jitter will not be similarly attenuated. Please consult the to the LTC6905, and the connection of RSET to VCC specifi cation tables and Jitter vs Frequency graph showing should be closely shared with the bypass capacitor. jitter at various divider ratios. The resistor RSET may be placed on the opposite side of the board from the LTC6905, directly underneath the
JITTER AND STRAY CAPACITANCE ON THE SET PIN
bypass capacitor.
(PIN 3)
3) If a ground plane is used, the connection of the LTC6905 The stray capacitance on the SET pin (Pin 3) should be to the ground plane should be as close as possible limited to 10pF or less to avoid increased jitter or unstable to the LTC6905 GND pin and should be composed of oscillation. multiple, high current capacity vias.
LTC6905 SUGGESTED CRITICAL COMPONENT LAYOUT
R C In order to provide the specifi ed performance, it is re- LTC6905 quired that the frequency setting resistor RSET and the supply bypass capacitor be placed as close as possible 6905 F02 to the LTC6905. The following additional rules should be followed for best performance:
Figure 2. LTC6905 Suggested Critical Component Layout
6905fd 9
APPLICATIONS INFORMATION JITTER AND DIVIDE RATIO
1) The bypass capacitor must be placed as close as possible At a given output frequency, a higher master oscillator to the LTC6905, and no vias should be placed between frequency and a higher divide ratio will result in lower the capacitor and the LTC6905. The bypass capacitor jitter and higher power supply dissipation. Indeterminate must be on the same side of the circuit board as the jitter percentage will decrease by a factor of slightly less LTC6905. than the square root of the divider ratio, while determinate 2) The resistor RSET should be placed as close as possible jitter will not be similarly attenuated. Please consult the to the LTC6905, and the connection of RSET to VCC specifi cation tables and Jitter vs Frequency graph showing should be closely shared with the bypass capacitor. jitter at various divider ratios. The resistor RSET may be placed on the opposite side of the board from the LTC6905, directly underneath the
JITTER AND STRAY CAPACITANCE ON THE SET PIN
bypass capacitor.
(PIN 3)
3) If a ground plane is used, the connection of the LTC6905 The stray capacitance on the SET pin (Pin 3) should be to the ground plane should be as close as possible limited to 10pF or less to avoid increased jitter or unstable to the LTC6905 GND pin and should be composed of oscillation. multiple, high current capacity vias.
LTC6905 SUGGESTED CRITICAL COMPONENT LAYOUT
R C In order to provide the specifi ed performance, it is re- LTC6905 quired that the frequency setting resistor RSET and the supply bypass capacitor be placed as close as possible 6905 F02 to the LTC6905. The following additional rules should be followed for best performance:
Figure 2. LTC6905 Suggested Critical Component Layout
6905fd 9