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issue: serial data transfer with EVAL-AD7609EDZ in stand alone mode

Question asked by Juergen@work on Jul 16, 2015
Latest reply on Aug 5, 2015 by KarenNE

Hello,

 

we connected the eval-ad7609edz standalone (without eval-ced1z) to a microcontroller eval board and configured it to get the data in serial mode. But we run in an issue. After some time (15 to 40 sec) it seems to switch by itself into parallel mode.

 

Did anybody use the eval-ad7609edz stable in serial mode?

Generally, is there a mode change (parallel <-> serial) during operation possible or provided? (we think it will be selected only one time during AD7609 startup!)

Does anybody have an idea why the ad7609 could change from serial to parallel mode during operation? (or maybe do interpret something wrong and we do have an other issue?)

 

Now some more details are following:

=============more details BEGIN==============================

We changed the following default configurations of eval-ad7609edz for stand alone and serial mode:

  1. SL7 - A: to get DoutA to J1-C5
  2. moved R3 -> R4: operation mode changed from parallel to serial mode

The eval-ad7609edz worked fine and stable together with the eval-ced1z (in parallel mode).

 

Connected to our microcontroller board it starts fine and works for around 15 - 40 sec in serial mode. The following scope screenshot shows CH(B) (CS) and CH(A) FRSTDATA (screenshot 1):

2015-07-14_AD7609_SerialMode-issue_CS-FirstDat_OK.png

In this phase everything works fine: the converted values are reliable.

After some time (15 to 40sec after startup) the following signal on FRSTDATA can be observed (screenshot 2):

2015-07-14_AD7609_SerialMode-issue_CS-FirstDat_NOK_smotthlySwitchToParalell.png

It seems a mode change from serial to parallel is preformed. The FRSTDATA is high more often => unstable state during mode change?.

After some time it is stable and looks like this (screenshot 3):

2015-07-14_AD7609_SerialMode-issue_CS-FirstDat_NOK_constantInParalellMode.png

We think the AD7609 is in parallel mode now?

 

We also checked the power Supply AVDD(+5V) at J1-ABC32 and it is stable, even around (screenshot 2).

At J1-ABC32 we measured around I(AVDD+5V)=15,5mA. At the moment the power supply is provided by a standard 78L05 (100mA max).

VDRIVE (J1-ABC8) is connected to 3,3V.

 

===================more details END============================

 

Thanks for any response in advance.

ragards

Gerhard

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