ADS7040: What is the state of the SDO pin when the chis is not selected (CS# is high)

Eugene Krakow

Part Number: ADS7040

I'd like to string together multiple of these devices, sharing the CLK and SDO lines between 3 devices and only having a unique CS# line per device, but I don't see any definition for the state of the SDO pin when not selected. I assume it goes into a high impedance state with some kind of weak pull up? Is this defined?

over 6 years ago

0 Michael Stout over 6 years ago

TI__Genius 16890 points

Hi Eugene,

See Figure 1 and the specification for tDZ_CSDO in the datasheet. The SDO pin goes to tri state when not being used.

Mike

0 Eugene Krakow over 6 years ago in reply to Michael Stout

Prodigy 40 points

I see the 5ns time to enter the trimode state, but I see no information on this state. I'm looking for some kind of pull up number/leakage current/something like this that describes the behavior in this state so I can ensure I'm not underdriving from the output of the SDO line when addressing 3 or so ADS7040 devices in addition to my device.

0 Michael Stout over 6 years ago in reply to Eugene Krakow

TI__Genius 16890 points

Hi Eugene,

There is not a number specified in the datasheet for the leakage while in tri-state. I looked in the design documents and characterization data showed they measured about 100nA. This is not a guaranteed or even specified number though, but it does give you an idea of what to expect.

Mike

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ADS7040: What is the state of the SDO pin when the chis is not selected (CS# is high)