PGA308: PGA308 registers can't read and write the same data

user5121996

Part Number: PGA308

Hi TI Engineer：

When we debug PGA308, we find that when VS=3.34V, VREF=3.25V, registers ZDAC and GDAC can write data,but we read the other data!

When the VS voltage is adjusted to the 3.27V voltage, the registers ZDAC and GDAC can read and write the same data.

What is the correspondence between VS and VREF voltage, and how does this affect the register read and write of 1W? Or is there a problem in the timing of 1W?

over 7 years ago

0 Arking Chiu over 7 years ago

Intellectual 790 points

Hi Team,

Have relation between the Vs and Vref ?

it cannot read/write ZDAC when Vref lower than Vs 0.09V.

0 Arking Chiu over 7 years ago in reply to Arking Chiu

Intellectual 790 points

update sch

0 Alex Davis over 7 years ago in reply to Arking Chiu

TI__Expert 6520 points

Hi Arking,

The PGA308 should be functional with a Vref input anywhere from 1.8V up to Vs. There shouldn't be any dependence on Vref/Vs for 1W transactions. It's possible that this is linked to the other question you've asked: If Vout is still loading the 1W bus, it's possible that different supply levels could be triggering one of the PGA308's fault detection comparators, causing the output to swing to a level where communication is possible.

If you could include a scope shot of the 1 wire bus (measured at pin 2, ideally) for both cases, that might help in troubleshooting.

0 user5121996 over 7 years ago in reply to Alex Davis

Prodigy 60 points

Hi Alex Davis:

At present, R308 is NC.
The high and low level voltage of 1W is normal, which is the same as that of VS voltage.

0 Alex Davis over 7 years ago in reply to user5121996

TI__Expert 6520 points

Does this issue persist across multiple PGA308 devices? It's possible that the unit has been damaged.

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PGA308: PGA308 registers can't read and write the same data