AD5754-SPI read

Hi dingpeng 

Looking at your waveforms, there seems to be a timing issue. The AD5754R input shift register samples data at the falling edge, and so setup time or transition of data should be set on the rising edge of your sclk. 

One more thing is to check if you are using an external reference or the internal reference of the DAC? the internal reference is off by default and you need a power-up command to enable it if needed.

And I want to clarify that during normal operation, AVDD =7V and AVSS = -7V, right?

Best regards,

Ian

Hi dingpeng 

Looking at your waveforms, there seems to be a timing issue. The AD5754R input shift register samples data at the falling edge, and so setup time or transition of data should be set on the rising edge of your sclk. 

One more thing is to check if you are using an external reference or the internal reference of the DAC? the internal reference is off by default and you need a power-up command to enable it if needed.

And I want to clarify that during normal operation, AVDD =7V and AVSS = -7V, right?

Best regards,

Ian

Thank you! I tried to set the transition of SPI data on the rising edge of sclk and it works. Thank you very much!

Hi dingpeng ,

Glad it worked out. With that, I'll close this issue. Thanks

Best Regards,

Den

Hi iandal !

  I have set the SPI write command that the output of OUTA is +5V  and it was tested by  Digital Multimeter which suggested the right result . Another problem is that I wrote  0x10_000F which means four channel DAC A/B/C/D are power-up ,but I can not read the power control register  back by setting 0x90_0000 and 0x18_0000. Hoe should I read the dac register back ?

STEP 1: set 0x10_000F for write 

STEP 2: set 0x90_0000  for read

STEP 3: set  NOP command 0x18_0000 to read back .But Ican not read the right register value back .

This is unusual. You are able to see voltage at the DAC output now, right? That means the power up command works, and you're just unable to do readback. You could check the SDO setup on your fpga. it should be able to read DVCC-0.5V (worst case) SDO output levels. so the trigger level of 2V on the SDO you should be able to see the data. 

Yes , I have seen voltage at the DAC output such as +5V. And I  can also  control the DAC output by setting DAC value register. The DVCC is 3.3V .The IO voltage of SCLK、SDIN、SDO、SYNC_N、LADC_N、CLR_N is 3.3V.