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LMK00804B-Q1: LMK00804B-Q1 - Queries in datasheet

Sri Viswa S
Prodigy 120 points
Part Number: LMK00804B-Q1

Hi,

Below are my queries.

1)The datasheet provided VOH and VOL for different supply voltages but the test current is not provided. Please provide the test current for the VOH and VOL

2)There is note given for VOH and VOL like "Outputs terminated with 50 Ω to VDDO/2." - Whether this means that 50ohm is pulled upto VDDO/2 at the output?

3)In the Pin description, the output impedance of Single ended clock output pins is given as 7ohm. What does the 7ohm imply?

Thanks

Viswa

  • 0
    TI__Genius 16845 points

    Hi Viswa,

    A1) Outputs are terminated to VDD/2. The output current is therefore IOH = (VOH-VCC/2) / 50, and IOL = (VOL-VCC/2) / 50

    A2) Yes, that is correct

    A3) 7ohm is the impedance of LMK00804B-Q1 output driver. For high speed signaling, you want to match the driver impedance plus series resistance to the channel for best signal integrity. For a 50ohm trace, use Rs=43ohm

    Kind regards,
    Lane

  • 0 in reply to Lane Boyd
    Prodigy 120 points

    Hi,

    Thanks for the reply,

    Below are my queries

    1)Once I calculated the IOH and IOL information. Can I calculate ROH and ROL as follows?

    ROH=(VCC - VOH)/IOH

    ROL=VOL/IOL

    2)Whether 50ohm will be present inside the chip or it is used externally as a testing condition for VOH and VOL?

    Thanks

    Viswa

  • 0 in reply to Sri Viswa S
    TI__Genius 16845 points

    Hi Viswa,

    A1) Yes, that is correct. We specify Zo = 7ohm in the datasheet. The datasheet only provides a minimum limit, not a typical value, so the calculation may be larger than actual device performance.

    A2) It is not present inside the chip, it is the external load.

    Kind regards,
    Lane