SI5317 Datasheet, PDF (15/50 Pages) Silicon Laboratories – Pin-Controlled 1_710 MHz Jitter Cleaning Clock

Si5317
3. Frequency Plan Tables
For ease of use, the Si5317 is pin-controlled to enable simple device configuration of the frequency range plan and
PLL loop bandwidth via a predefined look-up table. The DSPLL has been optimized for jitter performance and
tunability for each frequency range and PLL loop bandwidth provided in Table 9 on page 22.
Many of the control inputs are three levels: High, Low, and Medium. High and Low are standard voltage levels
determined by the supply pins: V_DD and Ground. If the input pin is left floating, it is driven to nominally half of V_DD.
Effectively, this creates three logic levels for these controls. See section 6. "Power Supply Filtering" on page 35 and
section 1.2. "Three-Level Input Pins (with External Resistors)" on page 9 for additional information.
3.1. Frequency Range Plan
The input to output clock frequency range is set by the 3-level FRQSEL[3:0] and FRQTBL pins. The CKIN and
CKOUT is the same frequency range as specified in Table 8. Due to the wide tunability of the Si5317, each
frequency plan provides overlap between adjacent settings. To select a frequency plan, the desired frequency
should be selected as close to the defined center frequency. In certain cases where the desired frequency is
exactly between two overlapping plans, either FRQTBL and FRQSEL can be used.
3.1.1. PLL Loop Bandwidth Plan
The Si5317's loop bandwidth ranges from 60 Hz to 8.4 kHz. For each frequency range, the corresponding loop
bandwidth is provided in a simple look-up table (see Table 9 on page 22). The loop bandwidth is digitally
programmable using the three-level BWSEL [1:0] input pins.
3.2. Output Skew Adjustment
The overall device skew (CKIN to CKOUTn phase delay) is adjustable via the INC and DEC input pins. A positive
edge triggered pulse applied to the INC pin increases the device skew defined by Table 8, INC/DEC step size, for
each given frequency plan. The identical operation on the DEC pin decreases the skew by the same amount.
Using the INC and DEC pins, there is no limit to the range of skew adjustment that can be made. Following a
powerup or reset, the overall device skew will revert to the reset value, although the input-to-output skew is
effectively random. The rate of change for each INC/DEC operation is defined by the selected loop bandwidth,
BWSEL[1:0].
Preliminary Rev. 0.15
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