HMC832LP6GETR datasheet(28/49 Pages) AD

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Data Sheet

HMC832

Using Exact Frequency Mode

If the constraint in Equation 16 is satisfied, the HMC832 is able

to generate signals with zero frequency error at the desired

VCO frequency. Exact frequency mode can be reconfigured for

each target frequency, or be setup for a fixed fGCD that applies to

all channels.

Configuring Exact Frequency Mode for a Particular

Frequency

1. Calculate and program the integer register setting

where the floor function is the rounding down to the

nearest integer.

2. Then calculate the integer boundary frequency

fN = NINT × fPD.

3. Calculate and program the exact frequency register value

where fGCD = GCD(fVCO,fPD).

4. Calculate and program the fractional register setting













−

VCOk

FRAC

ceil

)

(

where ceil is the ceiling function meaning round up to the

nearest integer.

Example: to configure the HMC832 for exact frequency mode

at fVCO = 2800.2 MHz, where the PD rate (fPD) = 61.44 MHz,

proceed as follows:

1. Check Equation 16 to confirm that the exact frequency

mode for this fVCO is possible.













≥

)

(

GCD

VCO

GCD

and

GCD

fGCD = GCD(2800.2 × 106, 61.44 × 106) =

120 × 103 >

= 3750

Because Equation 16 is satisfied, the HMC832 can be

configured for exact frequency mode at fVCO = 2800.2 MHz by

continuing with the remaining steps.

2. Calculate NINT

NINT = Register 0x03 =

2800

























floor

VCO

3. Calculate the value for Register 0x0C

3072

20000

)

100

(

)

((

−

GCD

VCOk

4. To program Register 0x04, the closest integer-N boundary

frequency (fN) that is less than the desired VCO frequency

(fVCO) must be calculated: fN = fPD × NINT. Using the current

example

fN = fPD × NINT = 45 × 61.44 × 106 = 2764.8 MHz, then

938000

9666560

)

2764

2800

(

)

(













−













−

ceil

VCO

Exact Frequency Channel Mode

When multiple, equally spaced, exact frequency channels are

needed that fall within the same interval (that is, fN ≤ fVCOk <

fN + 1) where fVCOk is shown in Figure 46 and 1 ≤ k ≤ 214, it is

possible to maintain the same integer-N (Register 0x03) and

exact frequency register (Register 0x0C) settings and only

update the fractional register (Register 0x04) setting. The exact

frequency channel mode is possible when Equation 16 is

satisfied for at least two equally spaced adjacent frequency

channels, that is, the channel step size.

To configure the HMC832 for exact frequency channel mode,

initially and only at the beginning, the integer (Register 0x03)

and exact frequency (Register 0x0C) registers need to be

programmed for the smallest fVCO frequency (fVCO1 in Figure 46),

as follows:

1. Calculate and program the integer register setting Regis-

ter 0x03 = NINT = floor(fVCO1/fPD), where fVCO1 is shown in

Figure 46 and corresponds to the minimum channel VCO

frequency. Then, the lower integer boundary frequency is

given by fN = NINT × fPD.

2. Calculate and program the exact frequency register value

fPD) = greatest common divisor of the desired equidistant

channel spacing and the PD frequency ((fVCOk + 1 − fVCOk)

and fPD).

Rev. A | Page 27 of 48

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