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TMS320F280049C-Q1: CMPSS DAC Static offset error

Koichi Saito
Intellectual 2525 points
Part Number: TMS320F280049C-Q1
Other Parts Discussed in Thread: TMS320F280049C

Hi Expert,

My Customer is referring to "Figure 7-51 CMPSS DAC Static Offset" and "7.10.5.1.2 CMPSS DAT Static Electrical Characteristics" in F28004x Datasheet(SPRS945F)

Customer question:

Q4) This question is related to Q2.
  "Offset Error" in Figure 7-51 is seen as "Approx. +300LSB" from dot line on the X-axis (DAC output ).
   On the other hand, "Static offset error" is shown as +25mV (MAX) in 7.10.5.1.2 CMPSS DAC Static Electrical Characteristics. +25mV equals to Approx. +31LSB when 3.3V 12bit.

  Is the +31LSB (+25mV) correct value that customer need to refer to ? And, Is the dot line of offset error in Figure 7-51 shown as just readable - customer should not calculate from the level of dot line ?

Q5) This question is regarding Note "(2) Includes comparator input referred errors" in 7.10.5.1.2 CMPSS DAC Static Electrical Characteristics.
  Is the "comparator input referred errors" an error happened at RAMP output/DAC12 input - RED circle or an error happen at comparator itself - BLUE circle in below diagram ?

      E2E_TMS320F280049C-Q1_ CMPSS DAC Static Gain Error_0527.xlsx

Best regards,
Saito

  • 0
    TI__Mastermind 28275 points

    Hi Koichi,

    Answers to your questions below:

    Q4) That is correct, 25mV is the spec. The figure is just for illustrative purposes, don't read any values from it.

    Q5) The compac output is not directly accessible to a user and it has to go through the comparator and hence any offset errors from the comparator will add to this. This is what the footnote is saying. The 25mV offset error spec for the compdac already includes comparator offset error.