AD5930 datasheet(21/28 Pages) AD

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AD5930

Rev. 0 | Page 21 of 28

To setup 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 1.

Note that if the part is only operating in continuous mode, then

Bit D7 in the control register should be set to 1.

External Increment, External Burst Control:

Both the increment interval (tINT) and the burst interval (TBURST)

are controlled by the CTRL pin. A 0 ≥ 1 transition on the CTRL

pin starts the sweep. The duration of CTRL high then dictates

the length of time the AD5930 bursts that frequency. The low

time of CTRL is the “listen” time, that is, how long the part

remains at midscale. Bringing the CTRL pin high again initiates a

frequency increment, and the pattern continues. For this mode,

the settings for Bit D13, Bit D12, and Bit D11 are ignored.

To setup 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 1, and INT/EXT INCR (Bit D5) must be set to 1.

Note that if the part is only operating in continuous mode, then

Bit D7 in the control register should be set to 1.

Interrupt Pin

This function is used as an interrupt during a frequency sweep.

A low-to-high transition on this pin is sampled by the internal

MCLK, thereby resetting internal state machines, which results

in the output going to midscale.

Standby Pin

Sections of the AD5930 that are not in use can be powered

down to minimize power consumption. This is done by using

the STANDBY pin. For the optimum power savings, it is

recommended to reset the AD5930 before entering standby,

because doing so reduces the power-down current to 20 µA.

When this pin is high, the internal MCLK is disabled, and the

reference, DAC, and regulator are powered down. When in this

state, the DAC output of the AD5930 remains at its present

value as the NCO is no longer accumulating. When the device

is taken back out of standby mode, the MCLK is re-activated

and the sweep continues. To ensure correct operation for new

data, it is recommended that the device be internally reset using

a control register write or using the INTERRUPT pin, and then

restarted.

OUTPUTS FROM THE AD5930

The AD5930 offers a variety of outputs from the chip. The analog

outputs are available from the IOUT/IOUTB pins, and include a

sine wave and a triangle output. The digital outputs are available

from the MSBOUT pin and the SYNCOUT pin.

Analog Outputs

Sinusoidal Output

The SIN ROM is used to convert the phase information from

the frequency register into amplitude information, which results

in a sinusoidal signal at the output. To have a sinusoidal output

from the IOUT/IOUTB pins, set Bit SINE/TRI (Bit D9) to 1.

Triangle Output

The SIN ROM can be bypassed so that the truncated digital

output from the NCO is sent to the DAC. In this case, the

output is no longer sinusoidal. The DAC produces a 10-bit

linear triangular function. To have a triangle output from the

IOUT/IOUTB pins, set Bit SINE/TRI (D9) to 0. Note that the

DAC ENABLE bit (D10) must be 1 (that is, the DAC is enabled)

when using these pins.

VOUT MAX

3p/2

7p/2

p/2

5p/2

9p/2

11p/2

VOUT MIN

Figure 34. Triangle Output

Digital Outputs

Square Wave Output from MSBOUT

The inverse of the MSB from the NCO can be output from the

AD5930. By setting the MSBOUTEN (D8) control bit to 1, the

inverted MSB of the DAC data is available at the MSBOUT pin.

This is useful as a digital clock source.

DVDD

DGND

Figure 35. MSB Output

SYNCOUT Pin

The SYNCOUT pin can be used to give the status of the sweep.

It is user selectable for the end of the sweep, or to output a 4 ×

TCLOCK pulse at frequency increments. The timing information

for both of these modes is shown in Figure 6 and Figure 7.

The SYNCOUT pin must be enabled before use. This is done

using Bit D2 in the control register. The output available from

this pin is then controlled by Bit D3 in the control register. See

Table 5 for more information.

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