ADF5902 datasheet(34/39 Pages) AD

34 / 39 page

ADF5902

Data Sheet

Rev. 0 | Page 34 of 39

FREQUENCY MEASUREMENT PROCEDURE

Use the following procedure to measure the output locked

frequency of the ADF5902:

In Register R3, set the readback control bits

(Bits[DB10:DB5]) to 26.

Read back the frequency counter value on DOUT and

record this value as Frequency 1 (see Figure 3).

In Register R7, set the CLK1 bits (Bits[DB23:DB12]) to

1808.

In Register R13, set the CLK2 bits (Bits[DB18:DB7]) to 10.

In Register R5, set the ramp on bit (Bit DB29) to 0.

In Register R13, Set the clock divider mode bits

(Bits[DB20:DB19]) to 2.

Allow a minimum delay of 428 μs (CLKDIV/fPFD (sec)).

In Register R3, set the readback control bits

(Bits[DB10:DB5]) to 26.

Read back the frequency counter value on DOUT and

record this value as Frequency 2.

Where Frequency 1 > Frequency 2,

Frequency Counter Value Delta = (216 − Frequency 1) +

Frequency 2.

Where Frequency 2 > Frequency 1,

Frequency Counter Value Delta = Frequency 2 − Frequency 1.

10. Calculate the output frequency using the following formula:

Output Frequency = (Frequency Counter Value Delta/

CLKDIV) × fPFD × NDIV × 2

where:

CLKDIV = ((CLK2 × 212) + CLK1).

fPFD = fREF/RDIV.

NDIV = INT value + (FRAC value/(225)).

11. Set Register R13 and Register R7 back to the original

settings and enable the ramp function in Register R5 if

required.

WAVEFORM GENERATION

The ADF5902 is capable of generating five types of waveforms

in the frequency domain: single ramp burst, single triangular

burst, single sawtooth burst, continuous sawtooth ramp, and

continuous triangular ramp. Figure 43 through Figure 47 show

the types of waveforms available.

TIME

Figure 43. Single Ramp Burst

TIME

Figure 44. Single Triangular Burst

TIME

Figure 45. Single Sawtooth Burst

TIME

Figure 46. Continuous Sawtooth Ramp

TIME

Figure 47. Continuous Triangular Ramp

WAVEFORM DEVIATIONS AND TIMING

TIMER

fDEV

TIME

Figure 48. Waveform Timing

The key parameters that define a ramp are



Frequency deviation



Time per step



Number of steps

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