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IWRL6432: RDIF Interface in 1.8 V IO Mode

LJKW
Prodigy 130 points
Part Number: IWRL6432
Other Parts Discussed in Thread: SN74AVC2T245

Good day, 

If I recall correctly, the IWRL6432Boost uses the power optimized 3.3 V IO topology: 

where VION = 3.3 V. 

In the datasheet I see the High Level output threshold is VION - 450 mV. 

So just to make sure I understand correctly, if we decided to change to the 1.8 V IO topology (where VION = 1.8V), do we expect the RDIF interface to have a High Level output threshold to be 1.35 V? 

Currently, we are using a LVDS driver that has the following recommended operating conditions:

The High-level input voltage of this LVDS driver is 2 V, which means this driver would not be compatible if we switched to the 1.8 V IO topology. 

In summary, I have two questions: 

1. Do we expect the RDIF interface to have a High Level output threshold to be 1.35 V if we operate with the 1.8 V IO Topology? 

2. Can you recommend any LVDS converters/drivers that are compatible with this RDIF interface operating with the 1.8 V IO Topology (Vcc = 1.8 V, VIH < 1.35 V)?

Thanks for you help

  • 0
    TI__Genius 9710 points

    Hi,

    We are looking into your question and will get back to you soon.

    Regards

    Ankit

  • 0 in reply to Ankit Mohanty
    Prodigy 130 points

    Good day, any update on this?

    There doesn't seem to be any LVDS drivers that operate at 1.8 V, so it seems like the RDIF interface needs to be level shifted?

    Could you please confirm whether you spot any issues with any of the level shifters below? We plan to use these level shifters with the SN65LVDS31MDREP LVDS driver. 

    MPN Bits Lower Voltage Upper Voltage Mbps
    SN74AVC8T245RHLR  8 1.4 3.6 320 Mbps (VCCA ≥ 1.8 V and VCCB ≥ 1.8 V) 
    SN74LVC8T245RHLR   8 1.65 5.5 200 MBps???
    SN74AXC4T245BQBR   4 0.65 3.6 Up to 380 Mbps Support When Translating from
    1.8 V to 3.3 V
    SN74AVC2T245 2 1.2 3.6 500 Mbps (1.8 V to 3.3 V Level-Shifting) 

    I am not to sure on the data rate of the SN74LVC8T245RHLR level shifter, but the others seem like they should be compatible? 

  • +1 in reply to LJKW
    TI__Genius 9710 points

    Hi,

    All the level shifters look fine. You can also use SN74AXC8T245PWR (High Speed 8bit) with SN65LVDS31MDREP LVDS driver. Below design uses SN74AXC8T245PWR High speed level shifter.

    Regards

    Ankit