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TPSM63606: Output Impedance when disabled.

K.I. Koo
Prodigy 15 points
Part Number: TPSM63606
Other Parts Discussed in Thread: TPS564257

I am going to use TPSM63606 and TPS564257.

My customer wants to perfectly disconnect the Vout line with their load by software command.

The (mechnical) power relay could be a solution, I think.

But if I disable the TPSM63606 and TPS564257 (EN pin), the ouput impedance becomes almost infinite. Am I right?

If right, I do NOT need to use Relay.

Please let me have your comments.

Best Regards,

K.I. Koo 

  • 0
    TI__Expert 3766 points

    Hi K. I. Koo,

    I can only speak for TPSM63606, but for the output impedance, will the device be powered (VIN>0) and disabled?

    Regards,

    Henry

  • 0 in reply to Henry Kou
    Prodigy 15 points

    Yes, Vin is 12V, and I will make the device ON or OFF by the control of EN pin.

    TI Data Sheet is saying about the EN Pin Function as below.

    ---------- below

    EN/SYNC (Pin-14) (Input) Precision enable input pin. High = on, Low = off. Can be connected to VIN. Precision enable allows the pin to be used as an adjustable input voltage UVLO. It also functions as the synchronization input pin. Used to synchronize the device switching frequency to a system clock. Triggers on the rising edge of an external clock. A capacitor can be used to AC couple the synchronization signal to this pin. The module can be turned off by using an open-drain/collector device to connect this pin to AGND. Connect an external resistor divider between this pin, VIN and AGND to create an external UVLO.

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

    Best Regards,

    K.I. Koo

  • +1 in reply to K.I. Koo
    TI__Expert 3766 points

    Hi K. I. Koo,

    I believe the device output impedance is hundreds of Mohms during operation when EN is ON, however when EN is OFF, the output impedance drops down to around 20kOhms where it may draw current from the load in certain cases. To be safe I would recommend finding a way to isolate VOUT from the load.

    Regards,

    Henry

  • 0 in reply to Henry Kou
    Prodigy 15 points

    Hi ! Henry,

    If 20Kohm, then I have to find a way for the isolation.

    By the way, I thought the output impedance when EN is ON is almost ZERO ohm.

    Am I wrong?

    In general, the output impedance of ideal voatage source is ZERO, isn't it?

    Best Regards,

    K.I. Koo

  • +1 in reply to K.I. Koo
    TI__Guru 50120 points

    Hi Koo,

    From our end TI does not have any parameter or tests that measures the output impedance of the device.

    If you want a true disconnect from VOUT pin to downstream circuit, it would be better to have a load switch for a more robust design. 

    Refer to app note (SLVA652) for more details on why a load switch may be preferable here (https://www.ti.com/lit/an/slva652a/slva652a.pdf).

    Regards,

    Jimmy 

  • 0 in reply to Jimmy Hua
    Prodigy 15 points

    The App Note you informed is a great help!!

    Thanks a lot, Jimmy

    K.I. Koo