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TPS65910: Vbackup, RTC, Bootmode

Sujay Arasegowda
Intellectual 660 points
Part Number: TPS65910
Other Parts Discussed in Thread: AM3351

.Hi,

I am using PMIC TPS65910A3A1RSLR in the design with AM3351.

I have below queries  

a. This PMIC has Vbackup pin and if coin cell battery of 3V is connected to this pin. Can i read the time from the serial port available in this IC?

b. in the boot mode Boot1=1 (High) and Boot0=0, (gnd), what are the output voltages in DC DC outputs and LDO's?

Thanks in advance

Regards

Sujay A

  • 0
    TI__Genius 10885 points

    Hi Sujay,

    a) The PMIC will not have i2c functionality within backup mode, but the RTC will continue to count. Once the PMIC is brought back into active mode the registers can be polled using i2c.

    b) The default settings for this boot mode are detailed in the TPS6910Ax User's Guide: http://www.ti.com/lit/ug/swcu093d/swcu093d.pdf

    User Guides for other TPS65910x parts can be found in the Technical Documents tab of the product folder: http://www.ti.com/product/TPS65910/technicaldocuments

    Regards,

    Rick S.

  • 0 in reply to Richard Solarski
    Intellectual 660 points
    Hi I went through the application notes swcu093d.pdf, Page 5 figute 1 (TPS65910A3A1) matches my requirement,

    My doubt is for AM3351 processor using DDR3L ram, if BOOT0= 0 and BOOT1=VRTC,

    1. Does all the outputs from PMIC IC will be the default voltage s as shown in Fig 1 of swcu093d.pdf
    2. i am using DDR3L ram and its voltage requirement is 1.35V/1.5V. From Fig 1 SWIO voltages are 1.5/1.8/2.5/3.3 V.
    If the Boot modes BOOT0= 0 and BOOT1=VRTC, What is its default output voltage?
    Can i connect the SWIO output to both processor VDDS_DDR and DDR3L RAM?
    3. Does the backup registers holds Date & Time when Vbat(main supply) is OFF and Vbackup is connected to 3V battery? Does the backup registers continues to update even the time and dates? Can i read these backup register for time and date, after the Vbat is available?

    Please help in the design.

    Regards
    Sujay A
  • 0 in reply to Sujay Arasegowda
    TI__Genius 10885 points

    Hi Sujay,

    1) Yes, the voltages are also defined in Table 2 of the User's Guide.

    2) The TPS65910A3 and TPS65910A31 will output 1.5V on VIO. You can connect to both VDDS_DDR and RAM as long as the current demand from the memory does not exceed the capability of the regulator. According to the AM335x datasheet, the max current for VDDS_DDR is 250mA, so 750mA continuous current can be supplied to the RAM.

    3) Yes, the RTC will continue to count even in backup mode and can be referenced after regaining i2c access.

    It's worth noting that the TPS65910A31A1 has a slight advantage over the TPS65910A3A1 if VRTC is used as a pull-up source to anything other than BOOT1, due to the higher VRTC current in off mode.


    Best Regards,

    Rick S.

  • 0 in reply to Richard Solarski
    Intellectual 660 points

    Hi Rick,

    i have used the same schematics of EVM (TMDSSK3358), ie. TPS65910A3.

    I tried powering ON the device with VRTC and VRTC_PMIC and input supply voltage with BOOT0= 0 and BOOT1 = VRTC_PMIC

    Schematic:PMIC1.pdf

    i Had powered up for 1st time. But there was no output, there are some pins which require VAUX33.

    Is it due to thus no output of VAUX33, there are no other outputs?

    Please help. Initially (First use- with no code in EEPROM) how should i power ON this IC to get the required output voltage.

    please refer my schematics (attached) and let me know if any wrong and how do i power On and which all pins to be connected where for first time bootup.

    Regards

    Sujay A

  • 0 in reply to Sujay Arasegowda
    TI__Genius 10885 points

    Hi Sujay,

    The TPS65910Axx devices require a start condition, such as push button press or assertion of PWRHOLD to start. Is the PMIC ignoring a valid start condition?

    Thanks,

    Rick S.

  • 0 in reply to Richard Solarski
    Intellectual 660 points
    Hi Rick,

    SW1 is the switch connected to pin33 (powerON).
    Powerhold I have tied to 5V externally, interrupt is tied to Vaux33, resetnrst is connected to controller gpio without any pullups.

    In this condition I have tried to power on by pressing the switch for 2 seconds but didn't help.

    Let me know anything else to be pulled high?

    Regards
    Sujay A
  • 0 in reply to Sujay Arasegowda
    TI__Genius 10885 points

    Hi Sujay,

    Is the VRTC LDO regulating at 1.8V? If this regulator is overloaded the PMIC may not be able to boot.

    Best Regards,

    Rick S.

  • 0 in reply to Richard Solarski
    Intellectual 660 points
    Hi Rick,

    I m getting the voltage at VRTC as 1.8V

    When i press the SW1, PMIC powers ON and all the outputs will be available. As soon as i release the switch, PMIC shuts down.

    Switch used is a tactile switch.

    Any idea on how to power ON.

    Regards
    Sujay A
  • 0 in reply to Sujay Arasegowda
    TI__Genius 10885 points
    Hi Sujay,

    It sounds like PWRHOLD may not be seeing the external 5V. Figure 6-1 in the datasheet shows the POWER enable logic in the top right corner. You can see that if PWRON is providing the enable condition it needs to be substituted by PWRHOLD or DEV_ON upon release.

    Descriptions for the power-on enable conditions are on the following page in the datasheet.

    Best Regards,
    Rick S.
  • 0 in reply to Richard Solarski
    Intellectual 660 points

    Hi Rick, 

    I have checked connecting the PWRHOLD to external 5V. Problem remains same

    As soon as i press the switch PMIC powers ON and output voltage appears, after a while PMIC goes OFF.

    Regards

    Sujay A

  • 0 in reply to Sujay Arasegowda
    TI__Genius 10885 points
    Sujay,

    Can you measure the delay from when NRESPWRON is asserted to when it shuts off?
    Can you read the INT_STS_REG register while holding PWRON? This will have to be within 8 seconds or the PMIC will shut off again.

    Best Regards,
    Rick S.