Datasheet

ADF4158 Data Sheet
Rev. E | Page 30 of 36
FREQUENCY
TIME
08728-029
Figure 40. Parabolic Ramp
The following example explains how to set up and use this
function.
Example
f
OUT
= 5790 MHz
f
DEV
= 100 kHz
Number of steps = 50
Duration of a single step = 10 µs
Ramp mode must be either triangular (Register R3, DB[11:10]
= 01) or single ramp burst (Register R3, DB[11:10] = 11).
In the first case, the generated frequency range is calculated as
follows:
Δf = f
DEV
× (Number of Steps + 2) × (Number of Steps + 1)/2
= 132.6 MHz
In the second case, the generated frequency range is calculated
as follows:
Δf = f
DEV
× (Number of Steps + 1) × Number of Steps/2
= 127.5 MHz
The timer is set in the same way as for its linear ramps
described in the Waveform Generation section.
Activation of the parabolic ramp is achieved by setting Bit DB28
in Register R5 to 1.
Next the counter reset (DB3 in Register R3) should be set first
to 1 and then to 0.
Eventually, the ramp must be activated as described in the
Activating the Ramp section.
Ramp Complete Signal To Muxout
Ramp complete signal on Muxout is shown in Figure 41.
08728-100
TIME
TIME
VOLTAGE FREQUENCY
Figure 41. Ramp Complete Signal on Muxout
To activate this function DB[30:27] = 1111 in Register 0 and
DB[25:21] = 00011 in Register 4
Interrupt Modes and Frequency Readback
Interrupt modes are triggered from the rising edge of TX
DATA
.
Depending on the settings of DB[27:26] in Register R5, the
modes in Table 7 are activated.
Table 7. Interrupt Modes
Mode Action
DB[27:26] = 00 Interrupt is off
DB[27:26] = 01 Interrupt on TX
DATA
, sweep continues
DB[27:26] = 11 Interrupt on TX
DATA
, sweep stops
When an interrupt takes place, the data consisting of the INT
and FRAC values can be read back via MUXOUT. The data is
made up of 37 bits, 12 of which represent the INT value and 25
the FRAC value.
The idea of frequency readback is shown in Figure 42.
FREQUENCYLOGIC LEVEL
TIME
TIME
TIME OF INTERRUPT
FREQUENCY AT WHICH INTERRUPT TOOK PLACE
INTERRUPT SIGNAL
LOGIC HIGH
LOGIC LOW
1. SWEEP CONTINUES MODE
2. SWEEP STOPS MODE
1 2
08728-030
Figure 42. Interrupt and Frequency Readback