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DS50PCI402 - Part heat-up and excessive current draw

sriram subburathinam
Prodigy 30 points
Other Parts Discussed in Thread: DS50PCI402

Hi All,

We have a design using DS50PCI402 PCIe equalizer. There are 3 equalizer parts in the design. The PCIe inputs are from an FPGA and the outputs terminate to a connector. There are 3 unused PCIe pairs, which are left floating.

When the board is first powered ON, we observed that very high current is drawn from the 2.5V supply fed to the equalizer and the part gets very HOT. 

In the design the 2.5V supply for equalizer is derived from a switcher, converting externally fed 3.3V. Initially the current draw from 3.3V supply is 2A. Suspecting the equalizer part, we have set one of the equalizer in power down mode by wiring PRSNT pin to 2.5V. This has reduced the current draw from 3v3 supply to 1.4A and the heating of that equalizer has stopped. Similarly wiring the PRSNT pin of the second equalizer part has reduced the current draw from 3v3 rail to 1A. Setting all 3 equalizers has reduced the current draw from 3v3 rail to 0.6A.

Has anybody faced similar issue?  Any suggestions to reduce the current draw, part heat-up is appreciated.

Thanks

Sriram SR

  • 0
    TI__Intellectual 1705 points

    Hi,

    When the DS50PCI402 is in normal operating, it typically consumes about 800mW (320mA at 2.5V supply).

    The input and output is CML, so when ENRXDET and RXDETA/B are tied high, the internal 50 ohm to VDD=2.5V is enabled.

    If input is tied to GND, there will about 50 mA of current thru each of the internal 50 ohm.

    The unused high speed input and output should be left open.

    Regards,

    Michael

  • 0 in reply to Michael Hinh
    Prodigy 60 points

    Hi Micheal,

      Thank you for the response. FYI, we removed those 0 ohm resistors used at the input. We tried running the device at 4.25 Gbps (device set to 5 Gbps rate). The part heats up and reaches easily to 50 deg celcius. We wanted to know if this is normal ? Please respond to us as soon as possible. We have a product Demo set up in the 1st week of Feb;

     

    Regards,

    Mohan

  • 0 in reply to jeyalakshmi kanniah
    TI__Intellectual 1705 points

    Hi,

    I did a quick measurement using a termometer of temperature at the top of the device package and it is about 36 deg C.

    The IDD is about 350mA with 2.5V supply (all channels enable with 50 ohm termination: ENRXDET, RXDETA/B=1).

    Are you measuring the same way? Also do all the devices measured shows the 50 deg C?

    If yes, then this is higher than what I am seeing and I think the channel that had the inputs shorted to GND may be damaged.

    Regards,

    Michael