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Original question:

TLV571 Control Registers

TLV571: Operate TLV571 with /CS, /WR, and /RD all tied low? (Approximate ADC0820-N's "RD Mode")

Aaron Holmes
Prodigy 50 points
Part Number: TLV571
Other Parts Discussed in Thread: ADS7882, ADC0820-N, , ADS7886, ADS7040, ADS8371

Curious to know if this is a supported thing to do. Does tying /RD low satisfy the requirement of the "dummy read" necessary to auto-config the device for 3V operation?  Will the conversion result appear on the data pins after /CSTART if /RD is tied low the whole time?  Or must /RD be pulsed as in the timing diagrams?

I'm basically looking for a 3.3V device that can operate in a mode similar to the TI ADC0820-N's "RD Mode," wherein all other control signals can be tied (to appropriate levels) and one need only toggle the /RD signal to both initiate a conversion and receive the result.  The TI ADS7882 is a near miss, as it requires 5V, and I'd like to avoid having to find (or create) 5V someplace.

All thoughts / suggestions much appreciated!

Very best,
Aaron

  • 0
    TI__Guru**** 176461 points

    Hi Aaron,

    Welcome to our e2e forum!

    Unfortunately no, you can't just tie the /RD pin low on the TLV571, you have to actively control that line along with the /CSTART pin.  Do you have to have a parallel output converter?  You are jumping between 8 and 12-bits with the TLV571 and the ADS7882 so let me know what sort of resolution and speed you need and I'll see if we have something that suits your needs.

  • 0 in reply to Tom Hendrick
    Prodigy 50 points

    Thanks, Tom!  Requirements are in line with the ADC0820-N:  8 bits, ~500ksps.  Mainly looking for a 3.3V answer to that part, if it exists.  Seems elusive!  Application depends on the 820-N's "RD mode," and I'm trying to minimize impact to the design while migrating away from 5V logic.  It may be time for a revolution, though.  Except for the very high speed pipelined parts, parallel's been in the rearview mirror for a while now, I know.  Though it comes with unnecessary (for me) extra bits, the '7882 is close, but if I still need the 5V for the analog half, I haven't made much progress.

    I am separately evaluating more invasive changes that would enable use of SPI parts, but wanted to investigate this angle also.

    Very best,

    Aaron

  • 0 in reply to Aaron Holmes
    TI__Guru**** 176461 points

    Hi Aaron,

    EDIT - Sorry, bad selection guide on my part.  [You might be looking at a serial device then, we don't have that many parallel parts in our portfolio.   A couple parallel devices you might look are the ADS7886 (12-bit) and the ADS8371 (16-bit).  For a serial option, you can look at the ADS7040.]

    Serial devices are ADS7886 and ADS7040 - the ADS8371 is parallel, but it needs 5VA.