CCS/TMS320F280049M: TMS320F280049M

Hi,

user4930554 said:

I want to know how we can connect the 3.0v between REF3030AIDBZR and VREFHIA,VREFHIB,VREFHIC in 64pin's TMS320F280049? need a IC_OPA_LMP7709MP or not? why?

The connection diagram is present in TRM of this device:

Regards,

Gautam

Hi user4930554,

Three comments:

1) The F280049M device has an option to utilize an internal ADC voltage reference.  As a result, an external reference does not need to be provided, unless the accuracy of the voltage reference does not meet your needs.  If you use the internal ADC voltage reference, please make sure you place a 2.2uF capacitor on the pin.  The F280049M controlCARD schematics (within C2000Ware) may serve as a good reference for you board design:
\C2000Ware_x_xx_xx_xx\boards\controlCARDs\TMDSCNCD280049M\A\

2) It appears that you are looking at the F28377D controlCARD (R1.1) as a guide for how to design an external ADC voltage reference.  Please note that there is a R1.3 of this design.  R1.3 has an improved reference circuit.

3) "why we not connect REF3030AIDBZR to the pin of VREFHIA,VREFHIB,VREFHIC direct" - this is because the transient load from the C2000 device's ADC may be more than the REF chip can handle.  By putting a opamp in voltage follower mode between the REF chip and the C2000 device, the ADC will give more valid ADC results.


Thank you,
Brett

Brett,

thanks your help, we found a readme.txt file in F2877D controlCAD(R1.3), the file told me that we need refer the circuit of F28379D(R1.3), we need a bigger capacitor than 2.2uF to connect to VREFHIA,VREFHIB,VREFHIC, the capacitor value is 22uF, it's so big value. I'd like to replace 22uf with two 10uF and a 2.2uf, the 2.2uF capacitor near the pin of VREFHIA,VREFHIB,VREFHIC.