not reaching FS with the DAC7513

DOV M.

Prodigy 200 points

Other Parts Discussed in Thread: DAC7513

Hi,

I am using the DAC7513 and some chips give a lower Vout than expected.

For example:

When I write FFF to the shift register I don't get the expected Vref at output .

For Vref = 293mV:

I get:

Vout = 284mV ( 4% error)

Again, this happens only on some chips, the others work fine.

Has anyone else experienced this?

over 14 years ago

0 Tony Calabria over 14 years ago

TI__Mastermind 43915 points

DOV M.

Can I see a schematic of your reference circuit? How are you filtering your reference signal before it is connected to the DAC?

Regards,

Tony Calabria

0 DOV M. over 14 years ago in reply to Tony Calabria

Prodigy 200 points

0 Tony Calabria over 14 years ago in reply to DOV M.

TI__Mastermind 43915 points

Are you measuring 0.293mV to the right of R33 (going directly into the DAC) or out of the ADR381ART?

Also, you may need to have a capacitor hanging off of the DAC VREF pin (in parellel with R34). A 1uF or 0.1 uF should work there and will improve the performance.

Regards,

Tony Calabria

0 DOV M. over 14 years ago in reply to Tony Calabria

Prodigy 200 points

Hi Tony,

I'm measuring the 0.293V going in to the DAC.

I'll try to add the capacitor on Sunday.

Thanks for all your help so far,

Dov

0 Bobi Hot over 14 years ago in reply to DOV M.

Prodigy 40 points

Hi,

I also recomended, when you have resistor division of a voltage, to use a opamp repeater, because the output current influence on the VRef, as can to view by the inside scheme.

0 Tony Calabria over 14 years ago in reply to Bobi Hot

TI__Mastermind 43915 points

Bobi is correct. You will need an op amp buffer (repeater) because of your voltage divider before your reference.

Regards,

Tony

0 Bobi Hot over 14 years ago in reply to DOV M.

Prodigy 40 points

Hi,

T do not a misunderstanding, I send a example, slightly paint your scheme:

Can and more improvements- cap to resistors.

Write what is the result?

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not reaching FS with the DAC7513