REF35: Negative reference voltage with REF35

Hi Jose,

Using an inverting op amp would provide the best driving capability and stability when generating a -2.5V reference. Can you share the application of REF35 here? Is it being used for a DAC reference or some other use?

Jose Jimenez said:

Is it possible to wire the device between GND and -5V rails, to generate -2.5V

Depending on the application, there might be other methods that don't require an op amp, but this would not be the correct way to do so. 

Thanks,

Jackson

Hello Jackson,

it is not used as an ADC/DAC reference. The application is a simple linear ramp generator. I am connecting the negative reference with a resistor to the virtual ground of an opamp integrator, like in the sketch below. Hence, the reference will be providing a constant current to the opamp without heavy transients.

I know some TI series references behave as shunt references when VIN and VOUT are wired together, but couldn't find any information of such use of the REF35. Is it possible wiring the device in that way?

Best regards,

Jose

Hi Jose,

Thanks for the quick response. It is not possible to configure REF35 in a shunt configuration as you have described, and you will need to use an op amp to generate a negative reference voltage.

Using a device like REF5025 (REF5025IDR) in a shunt configuration is possible if you would like to consider that option. More information on this method can be found on page 5-6 of this e-book:

www.ti.com/.../slyc147a.pdf

Thanks,

Jackson

Thanks Jackson for your prompt response,

What about using the REF34 as shunt reference? There is a similar question in the forum, but I think there is a missing wire from OUTF/OUTS/IN/EN to GDN in the proposed response,

https://e2e.ti.com/support/power-management-group/power-management/f/power-management-forum/1309010/faq-ref3425-negative-reference-voltage-with-ref34

I have checked the REF5025 device, however, we'd prefer to use the REF34 (if possible), in SOT23 package.

Best regards,

Jose

Hi Jose,

For this application, I would suggest REF5025IDR or REF5025IDGKR.

Thanks,

Jackson

Thank you Jackson, we will evaluate carefully the different options (including the inverting opamp, REF5025 in shunt mode, and others).

Could you, please, confirm whether the REF34 works in shunt mode?

Regards,

Jose

Hi Jose,

Lab verification on REF34 being used in shunt mode is still ongoing. If there are positive updates, I will re-open this thread at let you know. For now, please consider other options.

Thanks,

Jackson