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What to do with unused 5515 pins

A.Wilson
Intellectual 520 points

 We are entering a 5515 design in to our CAD system and would appreciate some advice on where to connect the unused pins listed below (the datasheet is fairly clear on the other 187 pins!).

1.  We are not using the USB peripheral and need to know what to do with the following pins:
 
    F13    USB_LDOI    Do I still need to connect power to this pin? (I understand that if I do it must be connected to the same supply as ANA_LDOI & DSP_LDOI)
                                            If not what should be done with it?
   F12    USB_LDOO  Should this be left unconnected or a bypass capacitor to VSS possibly?
                                 If not what should be done with it?
                                            Other USB Pins:
                                            Datasheet suggests G13, G12, F11, J12, H14, J14, G10, H12, H11, H10, H9, J13, H13, G8, G11 should be connected to ground VSS
                                            Datasheet suggest G9 is connected via a 10K to G10
                                            Datasheet suggests G14 is left unconnected
 
2.  We are not using the RTC peripheral either as a RTC or as a DSP clock source (an external clock source will be connected to CLKIN PIN A8) and need to know what to do with the following pins:
 
    C8    CVDDRTC    Do I still need to connect power to this pin?  If so can it be connected to DSP_LDOO, ANA_LDOO or USB_LDOO?
                                         If not what should be done with it?
    F8    DVDDRTC    Do I still need to connect power to this pin?
                                         If not what should be done with it?
  
    E8    WAKEUP     If unused where should this be connected?
                                        
                                         Other RTC Pins:
                                         Datasheet suggests connecting B9 to C8
                                         Datasheet suggests connecting A9 to VSS
                                         Spectrum Digital USB Stick reference design connects WAKEUP E8 to VSS via a 10K
 
3.  We are not using the External Memory Interface.  Can the following pins be directly connected to VSS? (datasheet suggests connection to VSS via a 10K resistor)
 
    D5    EM_WAIT2
    K6    EM_WAIT3
    G1    EM_WAIT4
    H4    EM_WAIT5
Regards, Andrew
  • 0
    TI__Expert 8065 points

    Hi Andrew,

    1. The USB _LDOI pin:  The C5515 has three LDOI pins and they are internally connected. So, you must connect the three LDOI pins to the same power source and the same power pain even though you are not using all of the three on-chip LDOs.

    2. USB_LDOO pin: You can leave this pin unconnected if you are not using USB.

    3. Other USB related pins: Please follow the suggestions of the datasheet.

    4. CVDDRTC pin: You MUST provide a voltage to this pin at any cases, otherwise the device won't work properly. CVDDRTC can be 1.3v or 1.05V. So you can't this this pin to LDOI..

    5. DVDDRTC pin : Pull this pin down to GND. you can't use RTC_CLKOUT and WAKEUP pin

    6. WAKEUP pin: Pull this pin down to GND. This pin can be configured as an output by software. Do not configure this pin as an output.

    7. RTC_XO and RTC_XI: If the RTC oscillator is not used, it can be disabled by connecting RTC_XI to CVDDRTC and RTC_XO to ground (VSS).

    8. EN_WAITx pins: I recommend connect these pins to GND via 10K ohm resistor.

    Best Regards,

    Peter Chung

     

     

  • 0 in reply to Peter Chung
    Intellectual 520 points

    Hi Peter and thanks for the reply.

    I have now partially tested my custom hardware and can verify your suggestions with one added warning.

    I connected CVDDRTC to USB_LDOO because I am not using either USB or RTC and the USB_LDOO outputs a convenient 1.3 volts and hence looks suitable for powering CVDDRTC.

    Originally I found that all three LDO outputs were not working (no output volts).  After a suggestion from Spectrum Digital that the LDO outputs are dependent in some way on CVDDRTC being powered up I reconnected CVDRTC to an independent 1.3V supply at which point all three LDO outputs sprang to life.

    It appears that the LDO outputs are dependent on CVDDRTC although I can find no mention in the documentation and I am wondering if you can confirm this behaviour?

    Regards, Andrew

  • 0 in reply to A.Wilson
    TI__Expert 8065 points

    Andrew,

    I am sorry I am late to answer your question. Somehow I missed the email about your question from this forum.

    Yes, It is a normal behavior. The CVDDRTC must have an independent power source. It cannot be supplied by any internal LDOs. RTC module has a POR circuit that initiate the internal LDOs.

    Best Regards,

    Peter Chung