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DS90UB936-Q1: Effects of externally created faults

Part Number: DS90UB936-Q1

Hi,

We are using DS90UB936-Q1 in the design. We are analyzing the effects of some faults.

We just want to confirm that these faults won't damage the device.

Fault:

Fault happening before the board is powered on: What happens when the oscillator input is not available to the device?

Our Analysis: CSI and I2C communication will not work. Device won't get damaged.

Fault happening during run time: What happens when the oscillator input is not available to the device?

Our Analysis: CSI and I2C communication will not work. Device won't get damaged.

Whether these are correct?

Thanks

Viswa

  • Hi Viswa,

    The 936 requires an externally supplied oscillator to the REFCLK pin, in order to meet jitter and stability requirements. And to ensure that all functionality of the device is reliable and meets the datasheet specs.

    There will be no damage to the device in either of your mentioned Fault cases, but it will not meet the requirements for qualified use.

    1. If no oscillator is inputted to the REFCLK pin at power-up, then the internal oscillator will be used to generate a backup internal reference clock at a nominal frequency of 25MHz ±10%. However, I2C and CSI communication across the FPD-Link cable will not be reliable/stable. You need to apply an external oscillator at REFCLK and follow the Power-Up Sequencing in the datasheet. There is also no danger that the device will be damaged. The only effect is that you will get unreliable data sent across the FPD-Link cable.
    2. If the oscillator input at REFCLK becomes unavailable during runtime, then the same issues mentioned previously will occur. The backup internal oscillator will be used and the I2C and CSI communication will become unreliable. The clocks for I2C and CSI rely on the REFCLK input. Your FPD-Link device will not be damaged, but you should issue a PDB reset once the REFCLK input returns.

    Best,

    Justin Phan