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AFE4490: Maximum external clock

Charles Steaderman
Prodigy 10 points
Part Number: AFE4490
Other Parts Discussed in Thread: AFE4403

Tool/software:

What is the maximum external clock frequency of the AFE4490? In order to avoid interference with other circuits in my design, I would like to clock the AFE4490 at 12 MHz. Is that acceptable?

  • 0
    TI__Intellectual 2250 points

    Hello Charles,

    Thank you for your patience.

    The external clock on the AFE4490 is 8MHz, with +/-10% tolerance, which is divided into a 4MHz clock internally. We do not support a 12MHz clock frequency. However, the AFE4403 performs the same function as the AFE4490 with a more flexible external clock; that chip would be able to tolerate a 12MHz external clock, and may work better for your application.

    Regards,

    Payton

  • 0 in reply to Payton Schubel
    Prodigy 10 points

    Thanks Payton. Do you happen to have a feature/specification comparison for the AFE4490 vs. AFE4403?

  • 0 in reply to Charles Steaderman
    TI__Intellectual 2250 points

    Hi Charles,

    Both chips are very similar; they both include an integrated PPG front end that supports one photodiode and two LEDs (in either H-bridge or push-pull configurations) with matching Rx supplies, Tx supplies, and output resolution. They also both containing automatic ambient cancellation features. The AFE4403 has slightly worse noise performance, and some additional restrictions and limitations in comparison to the AFE4490. Some additional differences are provided in the table below, though I recommend consulting the datasheets for more details:

    AFE4490 AFE4403
    External Clock 8MHz 4-60MHz
    Max PRF 5000 SPS 2000 SPS
    Footprint 40 pins, 36mm² 36 pins, 10.5265mm²
    LED Driver Current Up to 200mA Up to 100mA
    Number of LEDs 2 Up to 3
    LPF Cutoff Frequency 0.5Hz-1kHz 500Hz (fixed)
    Cable On/Off Detection Present Not Present