AD7760 datasheet(8/23 Pages) AD

8 / 23 page

EVAL-AD7760/AD7762EDZ

Rev. PrB | Page 8 of 23

SOFTWARE INSTRUCTIONS FOR NORMAL USE

Once the initial software installation has been completed, follow

these instructions for the general setup of the evaluation software

each subsequent time the system is used.

Note that the hardware must be powered up as per the

Hardware connections section before attempting the following

steps.

The download default location for the EVAL-AD7760/

AD7762EDZ evaluation software can be found by clicking

Start

> All Programs > Analog Devices > AD7760_2 >

AD7760_2

. If a location other than the default was used,

follow the path that was entered during setup.

The evaluation software GUI appears –see Figure 10 there

are five main control sections as described.

To start select the correct AD776x device from the drop

down box – selecting AD7760 or AD7762.

To Power up the AD7760/2device under evaluation, first

click the Power Mode drop down menu, and select either

‘Low Power’ or ‘Normal Power’. This will automatically

prompt the EVAL-CED1Z to write to the AD7760/AD7762

registers and power up the AD7760/2 device.

Figure 8.Power, Number of Samples, Decimation Rate and Modulator Mode

Control buttons.

Note that the external voltage supply connected to the

EVAL-AD7760/AD7762EDZ board will show

approximately~240mA in ‘Normal Power’ mode, and

approx ~170mA in ‘Low Power mode. Seeing this current

draw levels change, when switching between the power

modes also verifies that the communications between the

EVAL-AD7760/2EDZ and EVAL-CED1Z board are

operational.

The AD7760 or AD7762 device will power up in a default

decimation setting of 32. Change the Decimation Rate

setting by clicking on the Decimation rate drop down

control as shown in Figure 8. This allows the user to vary

the over sampling rate and implement the five (for

AD7760) on-chip decimation options offering from a

78kHz to 2.5MHz output data rate from the AD7760.

The user can specify the power mode, decimation rate, and

number of samples to be acquired (typically 65536

samples) by using the drop-down menus on the software

front panel. The software allows the number of samples

specified by the user samples to be viewed as a waveform,

histogram, or FFT.

The choosing the different decimation rates from the front

panel controls writes to the AD7760/2 control register 2 to

change the amount of decimation used in the second

internal FIR filter of the AD7760. This filter can be set

bypassed to enable decimate x8 mode or otherwise set to

decimate x2 to x32 in order to enable an overall decimation

rate of 16 to 256 for the AD7760 device.

Note that for the AD7762 device only operates in

decimation rates: Dec x32, Dec x64, Dec x128, and Dec x

256.

To show samples output by the EVAL-

AD7760/AD7762/EBZ evaluation board Click Sample or

Continuous

. Clicking Sample gives one set of samples, the

length of which is determined by the No. Samples selection

on the software front panel. Clicking Continuous shows

continuously updated samples of the analog input to the

device.

Figure 9.

10. It is important to ensure that the frequency of the DRDY

pulse on an oscilloscope (test point marked DRDY) is

checked so that it matches the frequency shown in the

Frequency

text box on the software front panel.

11. If at any stage these do not match, reset the AD7760/AD7762

evaluation board by pressing the RESET push button on the

evaluation board. Then set the decimation rate on the

software front panel to the correct default value.

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