ADF4159CCPZ datasheet(29/36 Pages) AD

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Data Sheet

ADF4159

Rev. B | Page 29 of 36

Delay Between Ramps

The ADF4159 can be configured to add a delay between bursts in

ramps. Figure 42, Figure 43, and Figure 44 show a delay between

ramps in sawtooth, triangular, and clipped triangular mode,

respectively.

DELAY

TIME

Figure 42. Delay Between Ramps for Sawtooth Mode

TIME

Figure 43. Delay Between Ramps for Triangular Mode

TIME

DELAY

Figure 44. Delay Between Ramps for Clipped Triangular Mode

Example

For example, to add a delay between bursts in a ramp, follow

these steps:

Enable the delay between ramps option by setting Bit DB17

in Register R7 to 1.

Delay the ramp by 5 μs by setting Bit DB16 in Register R7

to 0 and setting the 12-bit delay start word (Bits DB[14:3] in

as follows:

Delay = tPFD × Delay Start Word

Delay = 40 ns × 125 = 5 μs

If a longer delay is needed, for example, 125 μs, set Bit DB16 in

in Register R7) to 125. The delay is calculated as follows:

Delay = tPFD × CLK1 × Delay Start Word

Delay = 40 ns × 25 × 125 = 125 μs

It is also possible to activate fast lock operation for the first

period of delay by setting Bit DB18 in Register R7 to 1. This

feature is useful for sawtooth ramps to mitigate the frequency

overshoot on the transition from one sawtooth to the next.

To activate the ramp, see the Activating the Ramp section.

Dual Ramp Rates Mode with Delay

This mode combines the modes described in the Dual Ramps

with Different Ramp Rates section and the Delay Between

Ramps section (see Figure 45).

TIME

Figure 45. Dual Ramp Rates Mode with Delay

To enable this configuration,

Program the two ramp rates mode as described in the

Dual Ramps with Different Ramp Rates section.

Program the delay as described in the Delay Between

Ramps section.

Parabolic (Nonlinear) Ramp Mode

The ADF4159 is capable of generating a parabolic ramp (see

Figure 46).

TIME

Figure 46. Parabolic Ramp

The output frequency is generated according to the following

equation:

fOUT(n + 1) = fOUT(n) + n × fDEV

(14)

where:

fOUT is the output frequency.

n is the step number.

fDEV is the frequency deviation.

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