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v01.0910
PLLs WITH INTEGRATED VCO - MICROWAVE APPLICATIONS
EVALUATION BOARD OPERATING GUIDE
4.3.2
PassiveDC Loop Filter (default)
a
the Passivedc loop filter consists of c33, r13, c37, r3, r4, c64, r21, c61 and op-amp u5. it can be
configured by removing r12, r25, r26, c63, shorting r22, c62, leaving JP6 open, and powering +15V
on.
it should be noted that when a single positive supply is applied to the op-amp, the minimum Vco tuning
voltage of the Passivedc loop filter is limited by the common mode input voltage characteristic and
the gain of the op-amp. in order to avoid any problem in trying to utilize the Vco tuning voltage lower
than 2V, a small negative supply voltage, for example –1V, should be applied to the negative supply Pin
4 of the op-amp. Since Pin 4 is grounded on the evaluation board, it is difficult to change but can be
implemented in the customer board design.
Figure 6. PassiveDC Loop Filter
Order On-line at
www.hittite.com
For technical application questions: Phone: 978-250-3343 or
pll@hittite.com
A - 8
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