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ADS1115: Device Reset Operation during Supply Voltage Transient

Peiheng Liu
Prodigy 620 points
Part Number: ADS1115

Hi,

I am looking into an BMS system issue and have a few technical inquiries regarding the ADS1115-Q1 reset design. 

For the ‘power-down state’ in datasheet, the ADS1115-Q1 does not perform A-to-D conversion but digital interface would response to I2C master communications, right?

When the VDD of ADS1115-Q1 ramping up from 0 to the recommended range, what's the voltage threshold for the start of internal reset process? How long would it take for ADS1115-Q1 transiting to the power-down state after threshold hit? Also, when there is a down-slope transient on VDD, would there be any hysteresis for this threshold and any changes to the reset process?

Great thanks for your help! 

  • 0
    TI__Guru* 92655 points
    Peiheng,


    For the ADS1115-Q1, you are correct about the power-down state. If the device is in the power-down state, the ADC is turned off, but the device will still respond to I2C communications.

    For the power-on-reset (POR) process, The threshold is somewhere around 1.5V, but can have variation in voltage. Based on what I've seen, the POR is basic. It has an RC delay in the POR to give it some small hysteresis going low. Once the POR is tripped, this signal is sent through the device, I believe the device then powers down immediately, holding the digital in reset.


    Joseph Wu
  • 0 in reply to Joseph Wu
    TI__Prodigy 620 points
    Hi Joseph,

    Thanks for your prompt reply!

    I am checking the BMS in bench test. The VDD of ADS1115-Q1 is pretty stable during the relay switching period and continuous communication was also monitored on the I2C interface. So I think the interface components are properly functioning. I think checking the OS bit could help to determine whether POR is triggered or not if ADS1115-Q1 was set to continuous conversion mode previously.

    Are there any ways could help to tell the rest of ADS1115-Q1 in normal operation? For example, could reading some specific fields in the register map help to tell the analog part is functioning well?

    Peiheng.
  • 0 in reply to Peiheng Liu
    TI__Guru* 92655 points
    Peiheng,


    Is your customer testing an under-voltage condition where the digital may be functional and the analog is not? I'm not aware of any setting in the register map that would ensure that the analog is working. The only thing that I could think of is measuring a known voltage (like a reference) to test to see that the ADC is functional.

    I would note that the minimum operation is 2V. Operation below this voltage is not specified in any way.


    Joseph Wu

    P.S. I assume that BMS is battery management system?
  • 0 in reply to Joseph Wu
    TI__Prodigy 620 points

    Hi Joseph,

    You are right about BMS, customer is using ADS1115-Q1 to monitor voltage & current of the whole battery pack.

    The VDD supply voltage to ADS1115-Q1 seems fine in the bench test, so I was asking about if there are any register settings that could help to see the analog working or not. I would work on this and tried to eliminate ADS1115-Q1 from the malfunctioning causes.

    Peiheng.

  • 0 in reply to Peiheng Liu
    TI__Guru* 92655 points
    Peiheng,


    It might be easier to describe what problem the customer is seeing. If there is a problem or unexpected behavior, I'd need to know the exact problem, what the supply and input voltages are, and how the problem arises.

    At this point, I don't know what problem the customer with the device and it's hard to give explanations of what to expect from the ADS1115.


    Joseph Wu