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Application Note AN126E Mar 20, 2001
Phase Locked Loops (PLL) using a Charge Pump,
PLL's with High Divide-by-N Factors, and
Decimation Before Plotting
By Stephen H. Kratzet
Introduction PLL Example 1 -- The Charge Pump
A spreadsheet approach will be shown for designing a The 1st example is taken directly from a National
phase locked loop (PLL) that uses a charge pump. Semiconductor application note (Ref. 1). Figure 1 shows
Although the spreadsheet is specific to SystemView by what the PLL looks like in SystemView. To simulate the
ELANIX, it may be used for other PLL systems using a ma current sources in the charge pump, two step
charge pump. In SystemView, PLL's with a high divide- source tokens are used at the input to the charge pump:
by-N factor (greater than ~1000) will result in very long +5000 volts and -5000 volts Inside the charge pump,
plotting times. In these cases, decimation of the sink data there is a resistor in series with each of the 5000 volt
can dramatically speed up the plotting times. inputs. Each of the series resistors is set to e6 ohms.
Figure 1. A divide by 4,500 PLL with a charge pump, followed by a low pass RC filter.
AN126E Mar 20, 2001 SystemView by ELANIX Page 1 of 10
Other parameter values can be used for the current partial solution is to use a limit token from the Function
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