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Choice of photodiodes

Andrianirina Rakotomalala
Intellectual 400 points
Other Parts Discussed in Thread: OPT3004, OPT3002, ADS8861, LMH32401

Hi!

Thank you for advising me:

- A prime photodiode which has a low capacity (1pF), a good response time, and which can detect lights in the wavelength range 350 - 1100nm (visible + infrared).

- A second photodiode which has exactly the same characteristics as the first photodiode (capacity, dark current, response time, ...), but which only detects lights in the visible light range (thus eliminating infrared). If this second photodiode does not exist, thank you for offering me an anti-infrared filter that I can place above the first photodiode to eliminate the infrared.

  • 0
    TI__Mastermind 25895 points

    Hi,

    What is the application here? We have digital output light sensors which have the processing chain and photodiode integrated on the chip. Please see OPT3004 (visible) and OPT3002 (broad spectrum). Would this work for you?

    Best,

    Alex

  • 0
    Intellectual 400 points
    Hello Alex,
     
    Thank you for your very interesting email.
     
    These photodiodes are for medical application. In summary, I am developing an application to support the diagnosis of mental illnesses by detecting the biosignature obtained from the retinal signal. This new and unique application requires the design of a dedicated electroretinography device.
     
    My basic idea is to connect a photodiode (visible or boardspectrum) to the input of a differential TIA (LMH32401) which will be followed by a differential ADC (ADS8861) with an SPI interface. The choice of differential devices is to minimize common mode noise. But this design requires careful choice of devices because the photodiode and the TIA and the ADC must be compatible with each other.
     
    Your proposals interest me because the processing chain and photodiode are integrated on the chip, which minimizes the size of the circuit and will minimize noise. My only problem is that the output interface is I2C or SMBus, while I want to have an SPI interface.
     
    Do you have the same photodiodes with SPI interface? Otherwise do you have a device that can convert the I2C to SPI, while keeping the signal quality?
     
    Always counting on your collaboration,
     
    Cordially.
     
    Andrianirina Rakotomalala
    R&D
    gentec 60 ans v3
    60 ans au service de l’innovation
     
    2625 Avenue Dalton, Québec
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    De : Alex Bhandari-Young [mailto:bounce-4691324@mail.e2e.ti.com]
    Envoyé : 20 juillet 2020 11:52
    À : mmwave_sensors_forum@mail.e2e.ti.com
    Objet : Sensors forum: Choice of photodiodes
     

     
    A Message from the TI E2E™ support forums
    Texas Instruments

     

    Alex Bhandari-Young replied to Choice of photodiodes.

    Hi,

    What is the application here? We have digital output light sensors which have the processing chain and photodiode integrated on the chip. Please see OPT3004 (visible) and OPT3002 (broad spectrum). Would this work for you?

    Best,

    Alex

     
     

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  • 0 in reply to Alex Bhandari-Young
    Intellectual 400 points

    Hello Alex,

    Thank you for your very interesting email.

    These photodiodes are for medical application. In summary, I am developing an application to support the diagnosis of mental illnesses by detecting the biosignature obtained from the retinal signal. This new and unique application requires the design of a dedicated electroretinography device.

    My basic idea is to connect a photodiode (visible or boardspectrum) to the input of a differential TIA (LMH32401) which will be followed by a differential ADC (ADS8861) with an SPI interface. The choice of differential devices is to minimize common mode noise. But this design requires careful choice of devices because the photodiode and the TIA and the ADC must be compatible with each other.

    Your proposals interest me because the processing chain and photodiode are integrated on the chip, which minimizes the size of the circuit and will minimize noise. My only problem is that the output interface is I2C or SMBus, while I want to have an SPI interface.

    Do you have the same photodiodes with SPI interface?

    Otherwise do you have a device that can convert the I2C to SPI, while keeping the signal quality? Is this kind of conversion (I2C to SPI) done frequently?

    Always counting on your collaboration,

    Cordially.

  • 0 in reply to Andrianirina Rakotomalala
    TI__Mastermind 25895 points

    Hi Andrianirina,

    We do not have SPI devices, unfortunately, only I2C. We also do not have any SPI to I2C ICs that I am aware of. You may try posting another post in the multiplexers and switchers forum on e2e to check though. You could use an MSP430 with some firmware to convert from SPI to I2C as well potentially.

    Best,

    Alex