Current rating and Power sequence of VOXL-2 camera connector J6,J7,J8



  • Hello there,

    We are designing a custom camera for VOXl-2 carrier board for that we are in need of few information listed.
    1,Maximum current source by each power domain in camera connector
    2,The power sequence (Turn ON / OFF)
    3,I2C / SPI / GPIO signal voltage levels

    kindly provide the requested information as early as possible

    Thanks,
    Sakthivel


  • Dev Team

    Hi Sakthivel,
    This is unfortunately not a straightforward answer.
    Designing cameras based on MIPI CSI is not easy to do. So to help make sure your designs go smooth, please provide us with more info and we can help make sure you get it right.

    #1: Each DF40-pin is rated for 300mA, however, not all pins can source all that current at the same time. So, you might need to help provide us with more info here. What power rails do you need to use, what image sensor(s) are you hoping to use? And how many sensors are you planning on using at the same time. Are you still using some of the ModalAI sensors too?
    There are also SW dependencies on certain sensors working or not. Our SW team would have to check the device tree to be sure that sensor is supported and we have drivers for it.

    #2, mixed answer. Some are controlled by SW such as the VDD/AVDD/DOVDD rails (see my comment about about SW support) and some are always on based on the board power distribution, such as the 5V, 3.3V, VPH_PWR 3.8V, and VREG_S4A_1P8. SW controlled ones are set once the driver queries the device to be sure it is providing the correct voltage(s). For the always on power supplies, they are all present after reset and will stay on until the main power is removed.

    Again, you might need to let us know some more info. What do you need to use? We want to help validate your needs at the system level.

    #3 is on the website here: https://docs.modalai.com/voxl2-connectors/
    "All single ended signals on B2B connectors J3, J5, J6, J7, and J8 are 1.8V CMOS unless explicitly noted. All single ended signals on cable-to-board connectors J10, J18, & J19 are 3.3V CMOS unless explicitly noted."
    Regarding the QUP/GPIOs on J6, J7, and J8, not all modes are enabled yet in SW and that is in process, so please let us know what you would like to use and we can let you know our status for that support.

    Most often, we just design the sensor solution for our customers for a nominal NRE fee. We can then provide you with a tested and supported sensor solution to your mechanical specifications. We are actually in the process of trying to update our website for an image sensor flex submission form. No specific ETA yet for that, but your request is common enough to make us offer this service.

    Thanks!
    Vinny



  • @Vinny said in Current rating and Power sequence of VOXL-2 camera connector J6,J7,J8:

    please provide us with more info and we

    Hi Vinny,

    Thanks for your support!

    1, We need 1.2V / 1.8V/ 2.8V power domains for our sensor and ISP, In order to to turn on / off sensor and ISP properly we need a sequence, in our case 1.2V starts first and 1.8V and then 2.8V, in camera connectors J6,J7,J8 we able to find 1.2V / 1.8V/ 2.8V power domains does the power domains in connectors having any specific sequence ? and please mention the tolerance value of voltages.

    2, Our camera requires around 800mA from 1.2V and 500mA from 1.8V and 2.8V would the voxl-2 able to support the requirement?

    3, Regarding GPIO's we planned to boot the ISP through SPI interface but its mentioned in datasheet that SPI lines are not tested. could you please confirm on this?

    Thanks,
    Sakthivel


  • Dev Team

    Hi Sakthivel,
    Thanks for the extra info.
    I have a lot to write, so if anything is not clear, please let me know!

    1. The power rails are SW programmable to an extent, but for initial discovery of what image sensor is on the bus, oftentimes the power sequence is just "all at once", and very little is it required to then disable power and turn it back on to the correct sequence. I've only come across one vendor with one MIPI based sensor who specified a power sequence that could not tolerate "any order". Are you able to share what sensor you are using so we can explore that as well?
      We keep a fairly comprehensive listing of sensors, their power requirements, MCLK reqs, etc. If you'd rather not say the sensor part number, we can email you (using the email you registered with) and ask if you prefer.

    2. Seems like your image sensor is pretty powerful to use that much current. Is that really 3.2W total!!? Technically, the HW on the design is capable of providing that much current, but the DF40 connector pins are not rated for that much current. Each pin is only rated for 300mA. The 1.2V DVDD total ICC is capable of 1,200mA, the 1.8V DOVDD rail is capable of 600mA, and the 2.8V AVDD is capable of 600mA. But this is combined across all DF40 connectors in total, not on each one at the same time. If you really need 800mA at 1.2V from just one connector, you might need to use the higher voltage rails of 3.3V or 3.8V or 5V, and sub-regulate down with a DC/DC (NOT an LDO since you'll still use the 800mA). For example, 800mA at 1.2V is 960mW, so at 3.3V, that is only 290mA which is less than the pin rating of 300mA (but of course, add in efficiency losses, and you might exceed 300mA, so 5V or 3.8V might be better).
      So, it sounds like you might need a simple adapter circuit as follows:
      5V DC/DC to 1.2V, 1.8V and 2.8V.
      Use the PGOOD of that 1.2V DC/DC to enable further DC/DC's for 1.8V and 2.8V.
      Due to the fact 2.8V is a higher voltage, it will take longer to ramp, thus likely meeting the spec of ramping after 1.8V to 90% final value.
      If you want to make sure your DC/DC's are only on when the board boots up fully and goes into discover sensor mode, you can use the 1.2V, 1.8V, and/or 2.8V from our DF40's as enables of your first 1.2V DC/DC, then cascade the PG like I mentioned above. If you are concerned your DC/DC's are too noisy to meet sensor specs, you can always regulate to 0.15V-0.25V above the target rail, and throw in an LDO to meet the exact spec.
      It's all doable, and fairly straightforward. We do it all the time (see our Framos adapter offerings for Voxl for example). The only trick will be the CCI I2C lines will need to have an isolation device to convert the 1.8V Voxl2 DOVDD pull-ups to your local 1.8V IOVDD pull ups to make sure there is no back-feeding across the design's power domains. We use a simple I2C translator for this, but not all part numbers can translate to the same voltage, so be careful with part selection. The other control signals (MCLK, RESET_N, etc) just need a simple TTL translation buffer to convert to the new local 1.8V domain to prevent back feeding across power domains.

    3. SPI features are being added to these ports as that is the intended default scenario!! I'll have to pull in the SW team on this request to see if they can answer whether or not they are already enabled, or soon to be. I'll reply after I ping on them. I think we have other forum threads on that topic, so I'll report back.

    Thanks!


  • Dev Team

    Hi Sakthivel,
    I just heard from one of our SW engineers as follows:

    Yes
    https://docs.modalai.com/voxl2-linux-user-guide/#spi0---camera-group-0-spi
    However, we are going to change J8 to a UART in next release.
    The current download available is Voxl2 Platform Release 1.2.1-0.7 from downloads.modalai.com
    release notes: https://docs.modalai.com/voxl2-system-image/#121
    as of 1.2.0 the J6 and J7 SPI are available. J8 is too now, but next release it will become a UART.

    We will update our docs accordingly, and I think we have future plans to make J6-J8 buildable by the end user as either SPI or UART. So this switch of J8 to UART is likely a temporary one for users.


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