• State Resolved
  • Locked Locked
  • Replies 4 replies
  • Answers 1 answer
  • Subscribers 78 subscribers
  • Views 419 views
  • Users 0 members are here
Support feedback
Options
Options
Similar topics

This thread has been locked.

If you have a related question, please click the "Ask a related question" button in the top right corner. The newly created question will be automatically linked to this question.

Original question:

MSP430FR2433: Confirm the specification of "Brownout power-down level"

MSP430FR2433: DVCC rise time specification?

lloyd konneker
Expert 1790 points
Part Number: MSP430FR2433
Other Parts Discussed in Thread: TPS3839, TPS22860

What are the specifications for “DVCC rise time” for MSP430FR2433?

Many other family members have this specified (say a max and a min) in the data sheet, typically under “Power Supply Sequencing.” A search on “rise” in the data sheet “SLASE59D – OCTOBER 2015 – REVISED SEPTEMBER 2018” shows no apropos result.

Also, a footnote (1) to Table 5-2 in the same document says “A safe BOR can be correctly generated only if DVCC drops below this voltage before it rises” referring to Vbor,safe == 0.1V. I interpret this to mean only that a particular kind of reset (the BOR reset) will occur safely only if DVCC drops to that level. I assume that means that another kind of reset will occur (SVS reset) if DVCC drops below Vsvsh- but not below Vbor,safe of 0.1V. I don’t interpret that to mean that the chip might never come out of reset.

The context is a solar cell to super capacitor power supply, which can be very slow rising and falling. Currently I have designed in an external voltage monitor (TPS3839) and a load switch (TPS22860) to switch power to the MSP430FR2433. I am wondering whether I can eliminate those parts. Also, since TPS22860 does not have QOD quick output discharge, this design does not take DVCC below 0.1V when DVCC to the MSP430 is switched off. My one crude test shows that the MSP430FR2433 will start, brownout, and reset without those extra parts. But unless TI will specify the behavior, I will need to do extensive testing.

  • 0
    TI__Genius 13215 points
    Hi lloyd,

    The data in the datasheet SLASE59D table 5-2 is all what we have. You could see the Figure 5-4 for power cycle behavior with SVS, and BOR Reset.
  • 0 in reply to Wei.Jetim Zhao
    Expert 1790 points

    Thanks. I don’t really expect an answer, but I want to discuss it further.

    A search of the net will yield many discussions about this topic, even discussions about older TI parts that did have stricter requirements on DVCC rise time. Also, sales literature for TI voltage supervisor parts discuss the frequent need for external voltage supervisors. Also, the data sheet for some MSP430 parts does specify a “DVCC rise time” parameter (both min and max), and in the footnotes often specifies even stronger requirement for a “monotonic” rising DVCC. My search of the data sheets for MSP430FR2xx4xx parts (and other families) does seem to show that they consistently specify the power supply just as in the document you cited, without specifying a min or max DVCC rise time and without requiring monotonicity.

    Can one use the cited “Figure 5-4. Power Cycle, SVS, and BOR Reset Conditions” as a specification or as just an illustration? It shows a monotonic dip in DVCC (monotonic falling, then monotonic rising.) But it does not illustrate a non-monotonic, double dip in DVCC. Also, it illustrates only limited dV/dt values ( depending on whether the curve is continuous.)  Can one assume that something that is not shown in the illustration is safe?

    My larger question is: are the newer MSP430 parts better in this regard, or has the method of specification just changed?

    I suppose that, especially for a solar power supply, there is a small probability of a noisy and random DVCC curve for which a mcu and its SVS will not properly reset. So that to guarantee your system always resets you must use some external solution (an external voltage supervisor or a energy harvester) that DOES properly reset the mcu.

    I was hoping that TI had announced that whatever technology is in the external solutions has moved into the SVS onboard some MSP430 families.

  • 0 in reply to lloyd konneker
    TI__Genius 13215 points
    Hi lloyd,

    Thanks for your discussing. I would like give you a quick answer that the Figure 5-4 is only an illustration. The key parameters on the figure are shown in the Table 5-2. PMM, SVS and BOR, which gives parameter data test by TI.

    For your another question, I would say that every device could has different silicon design for different parameters. You can't compare the datasheets between different parts. Just use the provided parameters in the device datasheet for specific part.
  • 0 in reply to Wei.Jetim Zhao
    Expert 1790 points

    Yes, each device could have different silicon and different parameter *values*.  But I would hope that all devices would be tested the same way and have the same set of parameters.  Some devices have parameter "DVCC rise time" (with min equal to zero) and specify monotonicity, while other devices do not.  In other words, the data sheets are inconsistent in their form.  That inconsistency makes it harder for a user.  Harder because if a parameter is missing, a user might need to characterize the parameters themselves, testing many device instances before designing in the device, or might need to extensively functional test each part before shipping, to make sure it will reset properly under all power supply conditions.  Or design a power supply with a limited set of conditions (fast, monotonic rise time, and fast discharge time below 0.1V.)

**Attention** This is a public forum