Specifications

138 Intel
®
Atom™ processor CE4100 Ref# 420826
Platform Design Guide
Intel Confidential
How to test this VCXO tuning on board:
1. The VCXO should generate 27MHz with the control voltage in the midpoint of control
range.
2. While Sigma-delta register with half of the maximum range is programmed, the voltage
on the VCXO control pin should be +1.6V.
3. Check the waveform on the modulator’s output. Clock divider register might be needed
to appropriately program VCXO to meet correct frequency.
4. Check the control voltage at 90% and 10% of full scale, which should be around +2.8V
and +0.35V respectively.
5. Verify the oscillator’s output frequency is changing by at least 100ppm from nominal
frequency in both directions with a frequency counter and the tuning range is symmetric
around the nominal.
Note
When performing the measurement, never attempt to connect a probe to the pins of the
crystal. The right way is to probe and measure clock frequency with clock outputs from
the oscillator chip.