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PGA460: Interface Conditions Under Shutdown

Part Number: PGA460

Hello Team,

One of my customers are designing using the PGA460 and had a couple of questions about the state of the interface under a shutdown condition.

1)      Will the TX pin still have a weak pull-up to IOREG or does this shutdown to conserve power?

2)      If the RX input is held low and the device then shuts down will the device remain in shutdown, or will keeping the input low cause it to come out of shutdown?

Could you help clarify this? 

Thanks

  • Hi D_Bartlett,
    By shutdown, I assume you are referring to low-power mode (LPM).

    Only the RXD pin is pulled high via weak-pull up value of 100kOhm, and will always be pulled high regardless if the device is in active or in LPM. The interface block is one of the blocks not impacted by LPM mode, since the wake-up command must be triggered at the RXD or IO pin of the PGA460. As described in the datasheet, a high-to-low transition held low for at least 300us is required to wake-up the PGA460 from LPM:
    "The master device must generate a wake-up signal defined as a dominant pulse (logic 0) on the UART interface
    with a length of at least 300 μs. After the wake-up pulse is complete, at least one inter-byte space must be
    allowed before starting a UART transmission. Figure x shows an example of a UART wakeup."

    The UART bus is idle high, so unless RXD is constantly forced low by the master controller sending 0x00 (which it should not), Question 2 indicates an error in the master's UART implementation.