
AD5930 
Therefore, in this example, a time interval of 20 ns × 2047 = 40 μs 
is the maximum, with the minimum being 40 ns. For some 
applications, this maximum time of 40 μs may be insufficient. 
Therefore, to cater for sweeps that need a longer increment 
interval, time-base multipliers are provided. Bit D12 and Bit D11 
are dedicated to the time-base multipliers (see Table 12). A more 
detailed table of the multiplier options is given in Table 13. 
Table 13. Time-Base Multiplier Values 
D12 
D11 
Multiplier Value 
0 
0 
Multiply (1/MCLK) by 1 
0 
1 
Multiply (1/MCLK) by 5 
1 
0 
Multiply (1/MCLK) by 100 
1 
1 
Multiply (1/MCLK) by 500 
Rev. 0 | Page 20 of 28 
If MCLK is 50 MHz and a multiplier of 500 is used, then the 
base interval (T
BASE
) is now (1/(50 MHz) x 500)) = 10 μs. Using 
a multiplier of 500, the maximum increment interval is 10 μs × 
2
11  1 
= 20.5 ms. Therefore, the option of time-base multipliers 
gives the user enhanced flexibility when programming the 
length of the frequency window, because any frequency can be 
output for a minimum of 40 ns up to a maximum of 20.5 ms.  
Length of Sweep Time 
The length of time to complete a user-programmed frequency 
sweep is given by the following equation:  
T
SWEEP
 = (1 + N
INCR
) ×  T
BASE
Burst Time Resister (T
BURST
) 
As previously described in the Burst Output Mode section, the 
AD5930 offers the user the ability to output each frequency in 
the sweep for a length of time within the increment interval 
(t
INT
), and then return to midscale for the remainder of the time 
(t
INT
 – T
BURST
) before stepping to the next frequency. The burst 
option must be enabled. This is done by setting Bit D7 in the 
control register to 0.  
Similar to the time interval register, the burst register can have 
its duration as: 
A multiple of cycles of the output frequency 
A multiple of MCLK periods 
The address for this register is given in Table 14. 
Table 14. T
BURST
 Register Bits 
D15 
D14 
D13 
1 
0 
0 
D12 
x 
D11 
x 
D10 to D0 
11 bits of <0…10>  
Fixed number of output 
waveform cycles. 
11 bits of <0…10>  
Fixed number of clock 
periods. 
1 
0 
1 
x 
x 
However, note that when using both the increment interval 
(t
INT
) and burst time register (T
BURST
), the settings for Bit D13 
should be the same. In instances where they differ, the AD5930 
defaults to the value programmed into the t
INT
 register. 
Similarly, Bit 12 and Bit 11, the time-base multiplier bits, always 
default to the value programmed into the t
INT
 register. 
ACTIVATING AND CONTROLLING THE SWEEP 
After the registers have been programmed, a 0 ≥ 1 transition on 
the CTRL pin starts the sweep. The sweep always starts from 
the frequency programmed into the F
START
 register. It changes by 
the value in the 
F register and increases by the number of 
steps in the N
INCR
 register. However, both the time interval and 
burst duration of each frequency can be internally controlled 
using the t
INT
 and T
BURST
 registers, or externally using the CTRL 
pin. The options available are:  
1.
auto-increment, auto-burst control 
2.
external increment, auto-burst control 
3.
external increment, external burst control  
1.
Auto-Increment, Auto-Burst Control  
The values in the t
INT
 and T
BURST
 registers are used to control the 
sweep. The AD5930 bursts each frequency for the length of 
time programmed in the T
BURST
 register, and outputs midscale 
for the remainder of the interval time (t
INT
 – T
BURST
).  
To set up the AD5930 to this mode, CW/BURST (Bit D7) in the 
control register must be set to 0, INT/EXT BURST (Bit D6) 
must be set to 0, and INT/EXT INCR (Bit D5) must be set to 0. 
Note that if the part is only operating in continuous mode, then 
(Bit D7) in the control register should be set to 1.  
2.
External Increment, Auto-Burst Control  
The time interval, t
INT
, is set by the pulse rate on the CTRL pin. 
The first 0 ≥1 transition on the pin starts the sweep. Each 
subsequent 0 ≥1 transition on the CTRL pin increments the 
output frequency by the value programmed into the 
F register. 
For each increment interval, the AD5930 outputs each 
frequency for the length of time programmed into the T
BURST
register, and outputs midscale until the CTRL pin is pulsed 
again. Note that for this mode, the values programmed into Bit 
D13, Bit D12, and bit D11 of the T
BURST
 register are used.