DAC7614

Hi sunil,
Thanks a lot for the information.Now reference voltage are alll working but if we set 12 bit data D0 to D11 we will get data as follow

1. -2.5v if we set data value =0 which is correct actually.
2. 0v if we set data value to 1024 which is not correct becuase for 1024 value we should get -1.25v
3. +2.5v if we set data value to 2048 which is also not correct we should get 0v

pls suggest.Also only first DAC output is getting output other 3 not getting

Thanks
Pandurang Pai

Hi sunil
Awaiting for ur reply.i am not possible to get corrrct value.pls guide.

Pandurang,

Did you modify the circuit to not connect -2.5V to VADREFLO? Assuming that you put VADREFLO as 0V, and did not make any other change. Please confirm.

Note that the analog input voltage also cannot be lower than VADREFLO.

Regards, Sunil

Dear Sunil,
The only problem was we were giving vrefl and vrefh voltage from regulator and there was some resistor problem after correcting it it is working but only one channel is responding but with 11 bit value and other 3 channels are not working.We connected Vrefl to -2.5v and vrefH to + 2.5vH.We have set RESET to HIGH and RESETSEL to 0v.Pls suggest

Hi sunil.
We find that dac7614 is working with other controller such as lpc2148 but if we interface with tms570ls3137 we will get 1 bit missing we will get full +2.5 volt for 2047 value.we will get one bit missing such as 16 bit grts shift left by one.pls suggest as we are waiting for ur suggestions.

Thanks
Pandurang pai

Hi Pandurang,

What are the low- and high-reference voltages for the LS3137 MCU ADC? These would be the voltages at the ADREFHI and ADREFLO terminals on the LS3137 MCU. Note that the DAC7614 outputs -ve voltages as well, which cannot be input to the MCU's analog input channel as this would violate the recommended operating conditions specified in the MCU's datasheet.

I suspect that ADREFLO is 0V (GND) and ADREFHI is +5V. In that case, +2.5V would correctly give a conversion result of 2048.

Regards,
Sunil

Hi Sunil,
I am getting -2.5v for decimal value 0 and +2.5v for decimal value 2048.Also ADREFHi is +2.5 and ADREFLO is -2.5v.We are communicating between DAC7614 and TMS570LS3137 by SPI communication.


Thanks Pandurang Pai

Pandurang,

As I described before, ADREFLO on the MCU cannot be lower than VSSAD for the conversions to be correct. Is VSSAD connected to Ground on the PCB?

Regards,
Sunil

Hi sunil

Actually we connected vdd to +5 AND vss to -5 volt

Thanks
Pandurang pai

VSSAD min is -0.1V.