For the VCO upper limit frequency setting (B1_0x51) for VCO adjustment, a value larger than the one obtained from the calculation formula described in the data sheet is set in the register (B1_0x51). What are the specific advantages/disadvantages of setting the register (B1_0x51) to “0.75 MHz” or “48 MHz” when, for instance, the calculated value is 0.4 MHz?|FAQ|ROHM Semiconductor

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For the VCO upper limit frequency setting (B1_0x51) for VCO adjustment, a value larger than the one obtained from the calculation formula described in the data sheet is set in the register (B1_0x51). What are the specific advantages/disadvantages of setting the register (B1_0x51) to “0.75 MHz” or “48 MHz” when, for instance, the calculated value is 0.4 MHz?
- If the calculated value is 0.4 MHz, selecting 0.75 MHz makes the frequency more accurate whereas selecting 48 MHz will reduce the accuracy.
  Since the VCO calibration obtains the capacitance correction values at the lower and upper points, and calculates the capacitance correction value at the set frequency by linear interpolation, the error becomes larger as the calibration frequency range increases. Therefore, select a VCO upper limit frequency setting that is slightly wider than the operating frequency.
  Related Products: ML7344/ML7406 family, ML7345 family, ML7404, ML7414