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Two of TPS65930 LDO's outputs do not come up.

Faizul Bacchus
Intellectual 1895 points
Other Parts Discussed in Thread: TPS65930, OMAP3530

A customer using the TPS65930 device to power up the OMAP3530 processor. He is using 4.3V as the input voltage to the TPS65930 device including this as the inputs to the 4 external LDO's. The TPS65930 device power up and the three switchers come up OK at 1.2V , 1.2V and 1.8V. Two of the external LDO outputs also come up; VMMC1 = 3V, and VPLL1 = 1.8V. However the other two LDO's, VAUX2 and VDAC are zero volts. The REGEN pin is floating on this design. Can you say why these two LDO outputs might be at zero volts. This is on more than one board.

Thanks,

Faizul Bacchus.

  • 0
    TI__Genius 15100 points

    Hi Faizal,

    Not all LDOs are ON at power-up. You will have to manually turn it ON, set DEV_GRP to correct configuration. You can look at the tables in the power chapter to see the default LDOs status at power-up.

     

    Regards,

    Gandhar.

     

  • 0 in reply to Gandhar Dighe
    TI__Intellectual 1895 points

    Hi Gandhar,

    Thanks for the quick reply. Unfortunately, I do not follow you. I understand now that we have to turn on the LDO's. Can you be a little more specific on what tables, in which dcument. Also I am not a digital guy and I searched for DEV_GRP in both the OMAP3530 data manual and the TPS65930 data manual and found nothing so please explain a little more about this.

    Thanks,

    Faizul Bacchus

     

     

  • 0 in reply to Faizul Bacchus
    TI__Genius 15100 points

    Hi Faizul,

    Sorry, I thought you knew the available documents. Please check this link for all documents for the device - http://focus.ti.com/docs/prod/folders/print/tps65930.html

    You can provide these to your customers so they can look into other details if they want to. The Technical Reference Manual is at - http://focus.ti.com/lit/ug/swcu052c/swcu052c.pdf (this is under user guides). See table # 5-8, you will see that VAUX4 and VDAC are not powered up by default. You can find the DEV_GRP bits in the respective registers - VAUX2_DEV_GRP and VDAC_DEV_GRP, you can set the DEV_GRP field to 0b111.

    Let me know if you have more questions.

     

    Regards,

    Gandhar.