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HMC703LP4E
v02.0813
8 GHz fractional syntHesizer
For price, delivery and to place orders: Hittite Microwave Corporation, 2 Elizabeth Drive, Chelmsford, MA 01824
978-250-3343 978-250-3373 fax Order On-line at www.hittite.com
Application Support: pll@hittite.com
Required CP Offset = (2.5 10-9+ 4TPS) (Fcomparison) ICP where:
TPS: is the RF period at the fractional prescaler input
ICP: is the full scale current setting of the switching charge pump
Note that this calculation can be performed for the center frequency of the VCO, and does not need refinement for small
differences (<25%) in center frequencies. Also, operation with unreasonably large charge pump offset may cause Lock
Detect to incorrectly indicate an unlocked condition. To correct, reduce the offset to recommended levels.
Another factor in Fractional spectral performance is the choice of the Delta-sigma Modulator mode. Mode B is normally
recommended, as it allows higher PD frequencies and makes it easier to filter the fractional quantization noise. For low
prescaler frequencies (<1.5GHz), however, mode A can offer better in-band spectral performance. see
Reg 06h[0] for
DsM mode selection. Finally, all fractional synthesizers create fractional spurs at some level. Hittite offers the lowest
level fractional spurious in the industry in an integrated solution.
operational Modes
The HMC703LP4E can operate in a eight of different modes (
Reg 06h[7:5]), and supports
“Triggering” from 3 different
sources. The modes of operation include:
All modes require Fractional mode to be enabled except for Integer mode. Fractional mode allows fine frequency
steps. Exact Frequency mode allows precise fractional frequency steps with zero frequency error. FM and PM modes
can be used for simple communications links, with data rate limitations set by the loop filter bandwidth. The PM mode
also allows for precise incremental phase adjustments, which can be important in phased arrays and other systems.
Frequency sweep supports built-in one-way, two-way, or user defined frequency sweeps, useful in FMCW radar
applications.
Depending on the mode, the auxiliary registers
Reg 0Ah, Reg 0Ch and
Reg 0Dh are used for different functions, as
(eQ 4)