TMS320F28335: Behavioral questions

Carlos Silva85

Expert 4915 points

Part Number: TMS320F28335

Dear Colleagues,

Regarding the TMS320F28335, can I please have further clarification on the points below:

What device do the EMU0 and/or EMU1 emulation signals have to the device? Shall they be ‘stuck’ at either logic 0 or logic 1?
What effect does an open circuit VREF input have on the device?
What effect does a voltage at VREF other than the one expected by software configuration have on the device?

over 7 years ago

0 MatthewPate over 7 years ago

TI__Guru* 82750 points

Carlos,

EMU0 and EMU1 are normally kept at the VDDIO rail voltage(logic 1) during normal operation. There are emulation/boundary scan modes that can be activated if these pins are not "1" when TRSTn goes active. Additionally there are some profiling/emulation tools that can push a signal transition on these pins when certain code events happen.

We recommend and external pullup on both these pins when implemented in a system.

http://www.ti.com/product/TMS320F28335/datasheet/terminal-configuration-and-functions#IDwRW7-1bcsylv

I'm not clear on what is meant by signal VREF in this context, there is no pin/signal named VREF. Can you give some more info on this one?

Best,

Matthew

0 Carlos Silva85 over 7 years ago in reply to MatthewPate

TI__Expert 4915 points

Hi Mathew. The ADCREFIN pin. I suppose this is the output from the internal VREF. Does it need decoupling? Can it be left open? What happens if it is externally connected to a voltage different from that internally generated?

0 MatthewPate over 7 years ago in reply to Carlos Silva85

TI__Guru* 82750 points

Carlos,

ADCREFIN is a single pin input that replaces the internally generated BandGap reference to the ADC.

If the internal reference is used we recommend ADCREFIN be tied to ground(VSS) rather than just left floating. The datasheet mentions this here:

http://www.ti.com/product/TMS320F28335/datasheet/detailed-description#SPRS2306976

If is in use then there are 3 voltage options, 2.048V/1.500V/1.024V.

http://www.ti.com/product/TMS320F28335/datasheet/specifications#litSPRS230-0491

So long as the voltage on ADCREFIN does not exceed VDDA there is no issue with having a voltage on this pin and still using the internal reference (activated by a bit field in the ADC control regs).

Best regards,

Matthew

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TMS320F28335: Behavioral questions