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PGA308: Question about User's Guide: setting parameters

user6243139
Prodigy 180 points
Part Number: PGA308

Hello,

(1) At table 7-31;

For example, VREF=3.3V and COS VR[1:0]="01"; Resolution of the Coarse offset is 

(1/128)(VREF)(0.0427)=(1/128)*3.3V*0.0427=1.1mV

Is it correct?

And then, is the range correct below? (Is VREF integer [V]?)

(±100mV)(VREF/3)=±100mV*3.3/3=±110mV          

(2) At table 7-31; Can we set the register COS VR[1:0] other than '01' if VREF=3.3V?

If we can: Is there correct the resolution and the range below (VREF=3.3V and COS VR[1:0]='11' setting)?

 - Resolution: (1/128)(VREF)(0.0256)=(1/128)*3.3V＊0.0256=0.66mV

 - Range: (±100mV)(VREF/5)=±100mV*(3.3/5)=66mV

(3) At table 7-30;

For example, VREF=3.3V and COS VR[1:0]="01" setting, we change a value of the Coarse Offset and a formula of the Coarse Offset Program in the table to the resolution and the range the formula at (1) question. Is it correct?

Best regards,

KT

         

 

  • 0
    TI__Guru 55466 points

    HI KT,

    You are correct, if using the VREF=3.3V COS VR1='0' and COS VR0='1' offset resolution is 1.1mV, and the range is +/-110mV

    Per the PGA308 User Guide, the internal circuitry for the Coarse Offset DAC  is optimized, and specified/characterized for a given reference input range.

    Please see Table 3-1 with the recommended/optimal COS VR1 and COS VR0 settings for a given reference input range are as shown on table 3-1.

    If you are using the 3.3V reference input, the correct setting has to be selected with COS VR1='0' and COS VR0='1' as shown on the table below.  (Corrected typographical error 2-10-2020 in Red)

    The User guide recommends to use the COS VR1 and COS VR0 settings per table 3-1, and advises to select the settings to the closest voltage range in the table, so it is not recommended to use a different register setting for VREF=3.3V.

    Thank you and Regards,

    Luis

  • 0 in reply to Luis Chioye
    TI__Guru 55466 points

    Hi KT,

    Corrected a typographical error on the post above.

    Thank you and Regards,

    Luis