HMC833LP6GE Datasheet, PDF (32/61 Pages) Hittite Microwave Corporation – Built in Digital Self Test

HMC833LP6GE
v01.1012
FRACTIONAL-N PLL WITH INTEGRATED VCO
25 - 6000 MHz
with a phase offset. A phase offset is implemented by adding a constant DC offset current at the output of
the charge pump.
DC offset may be added to the UP or DN switching pumps using Reg 09h[21] or Reg 09h[22]. The
magnitude of the offset is controlled by Reg 09h[20:14], and can range from 0 to 635 µA in steps of 5 µA.
Down offset is highly recommended in fractional mode of operation. Integer mode of operation works best
with zero offset.
As an example, a PD comparison of f_PD = 50 MHz (20 ns period) with the main pump gain set at 2 mA, and
a down (DN) offset of -385 µA would represent a phase offset of about (-385/2000)*360 = -69 degrees.
This is equivalent to the divided VCO arriving 3.8 ns after the reference at the PD input. It is critical that
phase offset be used in fractional mode. Normally, down offsets larger than 3 ns are typical.
If the charge pump gain is changed, for example to compensate for changes in VCO sensitivity, it is
recommended to change the charge pump offset proportionally to maintain a constant phase offset.
Figure 47. Charge Pump Gain & Offset Control
1.12
Frequency Tuning
HMC833LP6GE VCO subsystem always operates in fundamental frequency of operation (1500 MHz to
3000 MHz). The HMC833LP6GE generates frequencies below its fundamental frequency (25 MHz to
1500 MHz) by tuning to the appropriate fundamental frequency and selecting the appropriate Output
Divider setting (divide by 2/4/6.../60/62) in VCO_Reg 02h[5:0]. Conversely the HMC833LP6GE generates
frequencies greater than its fundamental frequency (3000 MHz to 6000 MHz) by tuning to the appropriate
fundamental frequency and enabling the doubler mode (VCO_Reg 03h [0] = 1).
The HMC833LP6GE automatically controls frequency tuning in the fundamental band of operation, for
more information see “1.2.1 VCO Auto-Calibration (AutoCal)”.
To tune to frequencies below the fundamental frequency range (<1500 MHz) it is required to tune the
HMC833LP6GE to the appropriate fundamental frequency, then select the appropriate output divider setting
(divide by 2/4/6.../60/62) in VCO_Reg 02h[5:0]. Similarly, to tune to frequencies above the fundamental
frequency range (> 3000 MHz) it is required to tune the HMC833LP6GE to the appropriate fundamental
frequency, and then enable the doubler mode of operation (VCO_Reg 03h [0] = 1).
1.12.1
Integer Mode
The HMC833LP6GE is capable of operating in integer mode. For Integer mode set the following registers
a. Disable the Fractional Modulator, Reg 06h[11]=0
b. Bypass the Modulator circuit, Reg 06h[7]=1
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