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TPS65072 LDO control

Hongtao Yan
Intellectual 395 points
Other Parts Discussed in Thread: TPS65072

Hi:

I am trying to disable/enable the DCDC1/2/3 and LDO1/2 individually. But I realize that when I disable the LDO2, the DCDC1 and DCDC2 are also disabled. 

After I played with CON_CTRL register, I found out that DCDC_SQ2/1/0 affect this behavior.

If I set DCDC_SQ = 111, then disable LDO2 will also disable DCDC1/2. But I can disable DCDC1 without affecting LDO2

If I set DCDC_SQ = 101, then I can disable them individually.

From spec, DCDC_SQ should only affect the power up sequencing. Why does it also affect the individual channel on/off?

Is this a known issue? Is there any side effect if I set DCDC_SQ to 101?

Hongtao

  • 0
    TI__Genius 16870 points

    Hi Hongtao, 

    If you notice the timing sequence in Figure 52, you see the valid VLDO2 triggers the enable for the VDCDC 1 and VDCDC2. 

    What are you powering? Is it the Altas 4? 

    That sequence is designed for the Altas 4. If your load depends on that sequence then yes, there would consequences to changing the sequencing. 

  • 0 in reply to Michael Green
    Intellectual 395 points

    Hi Michael:

    the figure 52 shows the link between VLDO1 and VDCDC3.

    I don't see any diagram that showing the VLDO2 and VDCDC1/2. Which version of the document are you using? I am using rev G, May 2013.

    We are using TPS65072 to power some peripherals such as camera, accelerometer, LCD, GPS. The power on sequencing is not very sensitive, but we need to control the individual power rail on/off.

  • 0 in reply to Hongtao Yan
    TI__Genius 16870 points

    Hi Hongtao, 

    Figure 52 does show VLDO2 relation to VDCDC1 and VDCDC2. (See the picture below.) You are using the same revision as I am.

    Since, you don't require the sequencing of the TPS65072 then I would recommend to you that you consider one of the other TPS6507x devices. See Table 9 for the other options and sequences. Otherwise, there is nothing wrong with changing the sequence of the TPS65072 to meet your application needs.