DAC8831EVM: DAC8831EVM

Jerome Paulet

Part Number: DAC8831EVM
Other Parts Discussed in Thread: DAC8831, DAC8830,

When CS is low (so as to transfer new data with SPI), the DAC ouput falls down if the output was high and rises if the output was previously low.

All SPI timings are compliant with the datasheet.

SPI Clk is about 30MHz.

over 5 years ago

0 Uttam Sahu over 5 years ago

TI__Genius 14220 points

Hi Jerome,

Welcome to E2E and thank you for your query. Could you please share the power supply and jumper configurations for the EVM? Are you supplying external power for +5VA and -5VA? Please also let me know what are the output voltage values.

Regards,
Uttam Sahu
Applications Engineer, Precision DACs

0 Jerome Paulet over 5 years ago in reply to Uttam Sahu

Prodigy 60 points

Hi,

J3-3 : +5V
J3-4 : -5V
J3-5 = J3-6 = GND
J3-10 : 3.3V

W1 : 1-2 connected
W3 1-2 --> nLDAC always connected to GND
SW1 : UNI

0 Jerome Paulet over 5 years ago in reply to Jerome Paulet

Prodigy 60 points

1 : DAC output

2 : SDI

3 : SCLK (GND of probe not connected)

4 : nCS

0 Jerome Paulet over 5 years ago in reply to Jerome Paulet

Prodigy 60 points

resolved with driving nLDAC signal.
So, DAC8831 doesn't work with nLDAC tied to GND. what happens with the DAC8830 ?

0 Uttam Sahu over 5 years ago in reply to Jerome Paulet

TI__Genius 14220 points

Hi Jerome,

Glad to know that the issue was fixed. DAC8830 doesn't have an LDAC pin. The DAC output updates asynchronously with CS.

Regards,
Uttam

0 Jerome Paulet over 5 years ago in reply to Uttam Sahu

Prodigy 60 points

Hi Uttam,
The issue is fixed but I don't understand why. The DAC8831 datasheet describes that nLDAC pin could be tied to GND constantly. Is it false or i misunderstood something ?

0 Uttam Sahu over 5 years ago in reply to Jerome Paulet

TI__Genius 14220 points

Ok. I misread. Pulling nLDAC low should work perfectly fine. Just check for some loose connections etc.

Regards,
Uttam

0 Jerome Paulet over 5 years ago in reply to Uttam Sahu

Prodigy 60 points

Hi,
I don't succeed using DAC8830 or DAC8831 without nLDAC. I have always had the same signals, fully corrupted.
It's a problem because i have to use the DAC8830 (so without the nLDAC signal).
To resume, with the card DAC8831EVM, i send the same signals : if nLDAC is tied low permanently, the output is corrupted, if i drive nLDAC, the ouput is not corrupted.
I don't know where is the problem, but for the moment, I can't use the DAC8830 and it's an issue.

0 Muhammet over 5 years ago in reply to Jerome Paulet

Prodigy 40 points

Hi Jerome,

I had same problem with DAC8831EVM. I added serial termination resistor 30 ohm to the SPI connections. And the problem is solved. I can update DAC output when LDAC is connected to GND.

Muhammet

0 Uttam Sahu over 5 years ago in reply to Muhammet

TI__Genius 14220 points

Hi Jerome,

Do you have any update on this issue after checking any possible loose connection etc. with the nLDAC pin pulled-down?

Regards,
Uttam

0 Uttam Sahu over 5 years ago in reply to Uttam Sahu

TI__Genius 14220 points

Closing the thread now. You can reopen if you have an update.

Regards,
Uttam

Data converters

Data converters forum

DAC8831EVM: DAC8831EVM