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[ TPS2546 ] Rpd and Power Up Sequence

Kenichiro
Mastermind 9165 points
Other Parts Discussed in Thread: TPS2546

[ TPS2546 ] Rpd and Power Up Sequence

Hi,

My customer is now designing CDP port with TPS2546, can you help me to figure out the answer for my customer questions?

As my understanding, USB Host device is required to have 15kohm pull-down resistors (referred as "Rpd" in USB specification) on D+/D- port at the input port of its transceiver. For USB port design with TPS2546, these Rpd should be mounted on post TPS2546, means DM_OUT/DP_OUT side (not DM_IN/DP_IN side). Is my understand correct?

Also, on my customer system, microcontroller which attempts to control CTLx pins, is powered up earlier than VBUS is applied to TPS2546 IN pin. Does this cause any of damage to CTLx pins?

Thank you for your support in advance.
Regards,
Ken

  • 0
    TI__Intellectual 2795 points

    1. TPS2546 is a pass-thru MUX on the data lines in CDP/SDP mode and do not have the pull-down resistor in oTPS2546. For downstream port, the pull down resistor might be integrated into the host controller silicon, if no, your schematic is correct, place at DP_OUT/DM_OUT side.

    2. As long as the CTLx voltage within the recommend operation ragne, it is ok.

  • 0 in reply to Milo Zhu
    Mastermind 9165 points

    Hi Milo,

    Thank you for your prompt reply!, I will consult wit my customer.

    Regards,
    Ken
  • 0 in reply to Milo Zhu
    Mastermind 9165 points

    Hi Milo,

    Let me rever this, sorry. Now I would like to make sure the relation between IN pin and Data pins.
     
    Absolute maximum rates for data lines (DP_IN, DM_IN, DPOUT and DM_OUT) are specified as above.
    Since microcontroller is powered up earlier than IN voltage, there possibly certain voltage can be appeared on data lines earlier than IN voltage.
     
    If voltage appered at data lines is higher than (IN + 0.3V), it would case device damage. Is my understanding correct?
    Thank you for your spport.
    Regars,
    Ken
     
     
     
  • 0 in reply to Kenichiro
    TI__Prodigy 650 points

    Tanaka-san,

    IN+0.3V or 5.7V, either one is lower which is the max voltage.