HMC4069LP4E
v02.0316
2.9 GHz INTEGER-N SYNTHESIZER
(N = 2 - 32)
PFD Functionality
The phase frequency detector functionality of the HMC4069LP4E is such that it compares the rising edge the two
input signals (REF / VCO). This information is then used to pulse the ND and NU outputs depending upon which
input signal is greater in frequency.
Under normal operation the ND pin will be active when VCO frequency is greater than the REF frequency; NU would
remain constant. Conversly, when the VCO frequency is lower than the REF frequency, then NU would be active
and ND would remain constant. Here, the term “active” means that the output will on average, vary between 3 - 5V,
and the term “remain constant” means that the output will remain at approximately 5V.
INVERT Functionality
The INV pin effectively swaps the REF and VCO input signals, such that the NU and ND pin responses are
swapped. This has the advantage of easily correcting a layout issue if the loop filter op-amp inputs were swapped.
A logic “LOW” on this pin will configure the device for normal operation, and a logic “HIGH” cause the input signals
to swap. The evaluation board has a 10kΩ resistor pull up resistor to 5V. A jumper must be installed connecting the
INV pin to ground for normal operation.
Lock Detect Functionality
The LD pin is an open collector pulsed output transistor. It requires an external 1k pull up resistor to Vcc (5V), as
well as a simple RC filter.
Since the pin will produce very narrow pulses at each zero crossing of the REF and VCO input signals, filtering is
necessary to create an average voltage which can be used to drive an LED or system input logic. When the device
is “LOCKED”, that transistor will effectively be “OFF”, and the filtered output voltage will be “HIGH”.
Below is an example of an RC filter for the lock detect pin. The value of resistor “R” should be greater than 100Ω
to limit any surge current from flowing when the output transistor is “ON”. The value of capacitor “C” should be
selected such that the filter cutoff is much less than the REF frequency, but not excessively large (slow) that it will
inhibit detection of lock status.
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Phone: 781-329-4700 • Order online at www.analog.com
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Application Support: Phone: 1-800-ANALOG-D