HMC703LP4E Datasheet, PDF (24/58 Pages) Hittite Microwave Corporation – 8 GHZ FRACTIONAL SYNTHESIZER

v02.0813
HMC703LP4E
8 GHz fractional synthesizer
Then, for each frequency of interest, f_VCO:
4 Calculate the approximate value of N that is required: N = f_VCO/f_PD = N_INT + N_frac
5. Program N_INT into integer register Reg 03h

Note: There is no need to re-program N_INT if it has not changed from the previous set-point.
6. Program the fractional register, Reg 04h = Ceiling(N_frac*2²⁴)

where the ceiling function means “round up to the nearest integer.”
Example: To configure HMC703LP4E for exact frequency mode with channel spacing of 50 kHz, VCO frequency =
2000.200 MHz and f_PD =61.44 MHz:
1. f_gcd(61.44 MHz, 50 kHz) = 10 kHz (as above)
2. Calculate N_channels=f_PD / f_gcd = 6144. Program into Reg 0Dh (6144 dec = 1800 hex)
3. Set the modulator mode to Exact Frequency (SD_MODE in Reg 06h[7:5] = 2)
4. Calculate N = 2000.2 MHz / 61.44 MHz = 32.55533854 = 32 + 0.55533854
5. Program integer divisor N_INT (Reg 03h) = 32d = 20h
6. Program fractional divisor Reg 04h= CEILING(0.55533854 x 2²⁴) = 9,317,035 = 8E2AABh
In the above example, without exact frequency mode, there would have been a -1.2 Hz error due to quantization.
FM Mode
The HMC703LP4E PM mode supports simple FSK modulation via a level sensitive trigger. FM mode can be used for
simple communications links, with data rate limitations set by the loop filter bandwidth.
The HMC703LP4E is configured to operate in FM mode by writing Reg 06h[7:5] = 3.
The FM mode allows the user to toggle between two frequencies F₀ = N₁*f_PD and F₁ = N₂*f_PD based on the level of
the TRIG.
The following procedure is recommended to configure HMC703LP4E to FM mode:
1. Lock in fractional mode (Reg 06h[7:5]= 0) to F₀ = f_PD x (Reg 03h.Reg 04h).
2. Program (Reg 0Ch.Reg 0Dh) for F₁.
3. Change mode to FM (Reg 06h[7:5] = 3).
4. Select the trigger source Reg 06h[9] = 1, TRIG (pin-6), or Reg 06h[9] = 0 - trigger from SPI bit Reg 0Eh[0]
5. Switch between F₀ and F₁ on a trigger state 0/1 = F₀/F₁.
It is possible to change the next frequency state between trigger events, without affecting the output - ie. write the F₀
value while on F₁, or F₁ while on F₀ .
PM Mode
The HMC703LP4E PM mode supports simple bi-phase modulation via a level sensitive trigger. PM mode also supports
programmable phase steps via an edge sensitive trigger. PM modes can be used for simple communications links,
with data rate limitations set by the loop filter bandwidth.
The HMC703LP4E is configured to operate in all PM mode by writing Reg 06h[7:5] = 4. In general the modulation
phase step, ∆q, in either PM mode is given by
where x = Reg 0Ah.
�� =
x � 360
2²⁴
(deg)
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