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About calculation of the ISO7640FM's supply current.

Satoshi
Guru 19485 points
Other Parts Discussed in Thread: ISO7640FM

Calculation (by datasheet) and survey data are not matched about the ISO7640FM's supply current.

Are the following calculation methods mistaken?

----------------------------------------------------

［Condition］

　・Input:50MHz_clock（×4ch）

　・Vｃｃ:+3.3V

　・Cout:10pF max（Calculale are 5pF）

［Calculate］

○Input

Icc1＝0.388＋0.0312×f

    ＝0.388＋0.0312×100　（50MHz_Clock＝100Mbps）

　　＝3.508mA

×4ch：3.508×4＝14.032mA　【survey data：4mA】

○Output

Icc2＝3.39＋0.03561×f＋0.006588×f×CL

　　＝3.39＋0.03561×100＋0.006588×100×5

　　＝10.245mA

×4ch：10.245×4＝40.98mA　【survey data：21.3mA】

----------------------------------------------------

When right, what is the cause by which calculation differs from survey?

 

Best regards,

Satoshi

  • 0
    TI__Intellectual 2200 points

    Hi Satoshi,

    The ICC1 and ICC2 calculations shown in the datasheet are for all 4 channels taken together. That is, you should not multiply the result by 4.

    By survey data, do you mean lab measurement data? If your load is 10pF in your lab measurements, you should 10 for CL, not 5. Also, if there is any capacitve loading from board traces or probes, that capacitance should also be taken into account.

    Hope this help.

    Rgds,

    Anant