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AFE20408: Output switch and drain switch control

Yishan Chen
Intellectual 1930 points

Part Number: AFE20408

Tool/software:

Hi,

Some question customer want to ask here:

For output switch function:

DAC can be controlled by out0 and out1 but it also can be controlled itself, what is the different between these two control method?

Will the DAC0 output change when we Disable OUT0?

what is the clamp voltage? How do we set this voltage?

Do we have OCP in DAC output or current limit when DAC is short?

About Drain switch control, PAON will functioned in What VSS voltage during the start-up?

Yishan Chen

Thank you

  • 0
    TI__Genius 17230 points

    Hi Yishan,

    Firstly, I will describe the output "groupings" on this device. The AFE20408 has 4 output groups. Each group is comprised of 2 DACs and one OUT pin. For example, one group is DACA0, OUTA0, and DACA1.

    The DACs are each individually controlled by a Power Enable bit. The OUT pin is a switch that can connect to either DAC0, DAC1, or VSS. The status of the OUT pin does not affect the DAC outputs. 

    Each OUT pin can select a "CLAMP", or "off" voltage. The CLAMP voltage is the voltage you need to turn off the PA gate/drain. This voltage can either come from VSS (the most negative voltage in the system), or DAC1. DAC1 allows you to select a much more precise voltage for your off voltage.

    Once you select which CLAMP you are using, the OUT pin can toggle between DAC0 and CLAMP. So, this will either be DAC0 and DAC1 toggle, or DAC0 and VSS toggle.

    Since the DACs have individual output pins, the DAC output will NOT change when you toggle the OUT pin. They may fluctuate slightly from the fast switching, but they do not turn off. In addition, Over Current Protection is controlled by the DACs. Since the OUT pin connects to a DAC with a switch, the OUT pin shares the DAC OCP. The DAC has a selectable OCP of either 15mA, 30mA, 90mA, or 120mA.

    The PAON pin is grounded on startup. You will have to manually enable the pin through a register write.

    Let me know if you have any further questions.

    Thanks,
    Erin