ADS1292: Input voltage tolerance

Hi,

Analog input pins, according to datasheet page 6,  should be "Analog input to AVSS  between   AVSS – 0.3        AVDD + 0.3 V"

So, device-wise perspective, it should not damage the device as long as the current is also limited under ±10mA, mentioned in the same table.

May I ask why and what might be the concern?  There shouldn't be any high current go into analog input pins for 

1. it's an OpAmp inputs terminals, by design nature, very low current is allowed to go in.

2. any high(sub mA to mA) current travels around the path near the analog input pins is hazardous and dangerous to human subject.

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Yes, you can use AVDD – AVSS = 3 V as long as the current is limited, and in fact the section and tables in 6.5 Electrical Characteristics were carried out using AVDD – AVSS = 3 V (1)

"(1) Performance is applicable for 5-V operation as well. Production testing for limits is performed at 3 V."

Thanks

Hi ChienChun,

Apologies for the confusion.

The AVSS(13) and DGNG(24) pins will be connected to a 0V GND plane. The pins AVDD(12) and DVDD(23) will be connected to a 3V source.

If you connect the PGA1N(1) pin to 0V GND and the PGA1P(2) pin to 5V. Will it damage the CI?

If so, can I prevent it from being damaged by limiting the current in these pins PGA1N(1) and PGA1P(2)?

Thank you. And sorry if I was unclear at the beginning.

Best regards,

Jonathan

Hi

PGA1N is Analog input.

If the Analog input to AVSS is between AVSS – 0.3 and AVDD + 0.3 V AND Current has to be less&limited to Momentary ±100 mA AND Continuous ±10 mA, then it should be okay. 

But, please note 

(1) Stresses beyond those listed under Absolute Maximum Ratings may cause permanent damage to the device. These are stress ratings only, which do not imply functional operation of the device at these or any other conditions beyond those indicated under Recommended Operating Conditions. Exposure to absolute-maximum-rated conditions for extended periods may affect device reliability.

Thanks

Hi ChienChun,

Thank you for the detailed answer. 

And what about IN1P (4) and IN1N (3) pins? Is it the same?

If AVSS(13) and DGNG(24) pins are connected to GND, AVDD(12) and DVDD(23) are connected to a 3V source. Can't I connect IN1P(4) to a 5V signal and IN1N(3) to GND, as it is out of the AVSS range (between AVSS – 0.3 and AVDD + 0.3 V)?

So, there is no way to expose any of the inputs to any signal that could be greater than AVDD+0.3V directly. 

I just need your confirmation on this bigtime. Thank you in advance.

Best regards,

Jonathan

Hi,

if IN1P (4) and IN1N (3) pins are all analog input pins, yes, the same rules and rating should hold.

" Can't I connect IN1P(4) to a 5V signal and IN1N(3) to GND, as it is out of the AVSS range (between AVSS – 0.3 and AVDD + 0.3 V)?"

Correct, not suggested, not recommended as its outside the datasheet's recommended operating conditions.

"So, there is no way to expose any of the inputs to any signal that could be greater than AVDD+0.3V directly. "

Datasheet doesn't recommend, so any outcome or performance are not guaranteed, and could cause damage.

Thanks