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Query regarding AM3352 RTC, PMIC, SPI Boot and Ethernet Interface

Mitesh Parikh
Prodigy 80 points
Other Parts Discussed in Thread: TMDSSK3358, AM3352, SN74AUP2G08

Hi,

I am having few queries regarding AM3352 RTC and PMIC Power on behavior regarding TMDSSK3358 EVM.

1. The minimum required pulse width for RTC_PWRONRSTn pin of AM3352 as per the datasheet is 1msec. While in TMDSSK3358, RC Circuit is used to generate RTC reset signal, where value of resistor is 1K and capacitor is 0.01uF. We have calculated reset pulse generated using this circuit taking Vih(min) of AND gate SN74AUP2G08 and it comes to be around 4.7usec. Kindly suggest the suitability of using component values as per EVM. 

2. This is regarding PMIC TPS65910A3 circuit used in EVM TMDSSK3358.The PWRHOLD pin of IC is connected to VAUX33. But as per application note swcu093b.pdf, VAUX33 is by default OFF. Now the power on sequence of IC tells that on giving PWRON active low, the PWRHOLD is to be maintained high for device to remain turn ON. But in fresh board with no software, processor cannot write into PMIC register to enable VAUX33 supply and hence the device will turn ON. So when the device goes in ACTIVE mode after pressing PWRON switch low, are all the supplies generated (i.e. ON) or they need to be enabled through software. Kindly explain the working of PWRON signal. 

3. During SPI Boot using CS0- the list of pins configured by ROM are as below.

    cs  -> spi0_cs0  - To be connected to Chip select pin of SPI Flash

    MISO - > spi0_d0 -> To be connected to Data Output pin of SPI Flash

    MOSI -> spi0_d1  -> To be connected to Data Input pin of SPI Flash
    clk     -> spi0_sclk -> To be connected to Clock Input pin of SPI Flash

 Kindly confirm above connections are OK.

4. For using dual Ethernet with RMII interface, do we need to use external 50MHz oscillator and connect 50MHz clock output on RMII1 and RMII2 clock input pins of  am3352 and also on CLKIN pin of both the PHY ICs. Kindly suggest.

Awaiting for the reply at an earliest.

Regards,

Mitesh Parikh

 

 

 





 

 

 

  • 0
    TI__Guru**** 393215 points
    Hi Mitesh,
     
    1. The same circuit with these values is used in all the EVM platforms for AM335X. Please be aware of Errata Advisory 1.0.5 if you plan to use the AM335X internal RTC.
     
    2. This is regarding PMIC TPS65910A3 circuit used in EVM TMDSSK3358.The PWRHOLD pin of IC is connected to VAUX33. But as per application note swcu093b.pdf, VAUX33 is by default OFF. Now the power on sequence of IC tells that on giving PWRON active low, the PWRHOLD is to be maintained high for device to remain turn ON. But in fresh board with no software, processor cannot write into PMIC register to enable VAUX33 supply and hence the device will turn ON. So when the device goes in ACTIVE mode after pressing PWRON switch low, are all the supplies generated (i.e. ON) or they need to be enabled through software. Kindly explain the working of PWRON signal. 
     
    2. Please check the PMIC datasheet (SWCS046Q) Figure 4. The PMIC also turns on when input voltage is applied. The PWRHOLD pin should normally be connected to AM335X pin PMIC_POWER_EN. PWRON is for turning the PMIC on/off when there is continuous input supply.
     
    3. Yes this is correct.
     
    4. Yes, please check Errata Advisory 1.0.16.