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DAC8555: RSTL pin confusion

Evert Dek
Prodigy 50 points

Part Number: DAC8555

Hi,

I'm a bit confused about the use of the RSTL and /RST pin.

In the datasheet on page 4 the RSTSEL pin is used for coding binary or 2's complement. And the /RST pin for the zero scale after reset.
On page 17 the RSTSEL pin is used for zero scale after reset.

What is the correct function for the RSTSEL pin?

I need midscale after reset.

  • 0
    TI__Guru 55743 points

    Hi Evert,

    It actually does both.  Basically, at startup, the device checks the RSTSEL pin to decide if it is in straight-binary or 2s-complement mode.  By default, the DAC loads code 0x0000 as the default output code.  In 2's complement mode, the most-significant bit is inverted to convert back to straight binary.

    So 0x0000 in 2's complement becomes 0x8000 in straight binary which is midscale.  

    So at startup with RSTSEL = 1, the output would be basically VREFH/2 (assuming VREFL is 0V).  

    Thanks,
    Paul

  • 0 in reply to Paul_Frost
    Prodigy 50 points

    Thanks,

    Regards

    Evert