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LMH0346 Datasheet does not have DC spec. for VCCO.

Naji Naufel
Intellectual 805 points
Other Parts Discussed in Thread: LMH0346

Hi,

The Block Diagram in the datasheet shows the differential outputs of the LMH0346 powered by VCCO. The application circuit examples show VCCO connected to a 3.3V supply.

Figure-4 contradicts the Block Diagram and VCCO pin description, and shows the output driver powered by VCC.

Q1. Is the output driver powered by VCCO or VCC?

Q2. Since the outputs are LVPECL compatible, can VCCO be connected to a 2.5V supply (assuming it powers the output driver)?

Q3. Why is the VCCO spec. missing from the DC Electrical Specs.?

Q4. VCMO is spec'ed as VCC-VSDOD. Shouldn't that be VCCO-VSSDOD?

Thank you

Naji

  • 0
    TI__Expert 4400 points

    I have moved this post to the High Speed Interface Forum where it is more likely to be seen.

    VCC and VCCO are really the same.  The VCC spec includes VCCO.  There is only one power bus for the LMH0346; all circuits operate with the same supply rail.

    1)  The output driver is powered by VCC (VCCO = VCC). 

    2)  Unfortunately, no.  It is not possible to separate the supplies and operate the CML outputs with 2.5V.

    3)  The VCC specifications include VCCO, so please refer to the VCC specs for VCCO.

    4)  The VCMO specification is the same either way since VCC and VCCO are the same. 

    I apologize for the confusion.  The VCCO nomenclature is there to show that these two supply pins are closest to the outputs and should be treated appropriately (e.g. careful supply bypassing) for a clean, low-jitter output.

    Gary Melchior