The ADF4000 series devices allow the Charge Pump voltage to be higher than the digital supply to the chip, many devices allow Vp as high as 6V, even when the digital part of the device is operating at 3V. With the newly released ADF4113HV you can have Vp as high as 16.5V. This allows a greater range of VCO tuning voltages.
Tip - saturation at the output of the charge pump can significantly degrade the lock time of the PLL. Ensure that you have sufficient headroom at both ends of the VCO tuning range. Use ADI SimPLL to check for clipping on the transient 'spikes' when tuning to frequencies at either end of the tuning range.
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发表于 2011-2-22 16:02:45
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