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OPT3001: Pullup resistor on INT pin

Zach Kimble
Intellectual 1075 points
Part Number: OPT3001

Tool/software:

Hello,

The datasheet recommends a 10k pullup resistor on the INT pin. I am working on a battery powered application so I need the power consumption to be as small as possible. Would using a larger resistor, such as 100k, have any effect on the device other than extending the rise time by 10x?

Best regards,

Zach Kimble

  • 0
    TI__Genius 10070 points

    Hi Zach,

    The recommendation for a 10k pullup resistor is also to ensure proper I2C timing. Please ensure that the timing requirements in section 6.6 are not being violated. What are the system power consumption requirements? In full-scale lux conditions the OPT3001 has a typical active current of 3.7 µA.

    Best regards,
    Nicole

  • 0 in reply to Nicole Khoury
    TI__Intellectual 1075 points

    Hi Nicole,

    Thank you for your quick response. If I am not planning to use I2C in tandem with the INT pin, do I still need to meet the timing requirements shown in section 6.6 for the INT pin? My plan is to use the interrupt signal's falling edge to wake up a microcontroller, which will then perform some action and go back to sleep. I plan to use OPT3001 in Transparent Hysteresis-Style Comparison Mode so the INT pin will go back to high impedance on its own once the light intensity falls below a certain threshold. 

    This is for a battery powered application so I need the power consumption to be as low as possible. The MCU and OPT3001 will be on battery power while the rest of the system is powered by the board power (when it's plugged in). I can't have an I2C bus be pulled up to the battery power because that will drain the battery quicker if I2C is used throughout the lifetime of the system. Instead, I plan to have an I2C bus that is pulled up to the board power and I will only use I2C while the board power is connected. I was thinking that when the system is built, it can be plugged in and the CPU can program OPT3001 via I2C. Then, when board power is disconnected for shipment, OPT3001 will not lose power because it's on battery power so it will keep those settings indefinitely. Later, when board power is applied again, the CPU will use I2C to communicate with the MCU (and OPT3001 if necessary). Please let me know if you see any issue with this plan.

    Best regards,

    Zach Kimble

  • 0 in reply to Zach Kimble
    TI__Intellectual 1075 points

    Hi Nicole,

    One additional question, when you say that the active current is 3.7uA for full-scale lux conditions, do you mean the maximum lux value the device can read (83865.6 lux) or do you mean whatever is the maximum of the currently selected FSR?

    Best regards,

    Zach Kimble

  • +1 in reply to Zach Kimble
    TI__Genius 10070 points

    Hi Zach,

    The full-scale current refers to the typical power consumption for the maximum lux value that the device can read.

    Can you provide more context regarding keeping the OPT3001 board on battery power? Will this only be for shipment purposes? 

  • 0 in reply to Nicole Khoury
    TI__Intellectual 1075 points

    Hi Nicole,

    Thank you for confirming. I would prefer not too give too many details about the application here so I will follow up with you via email.

    Best regards,

    Zach Kimble