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TPS62240: SOT-23 MODE function?

Martin55843
Intellectual 400 points
Part Number: TPS62240
Other Parts Discussed in Thread: TPS62260, TPS62821, TLV62568, TPS62561, LMR10510, TLV62585, TLV62569

Does the SOT-23 version of the TPS62240 have fixed-frequency enabled or disabled? The mode pin is missing, how is it wired up internally?

Enhancement request: Clarify this in the datasheet:

"This pin is only available at WSON package option. MODE pin = High forces the device to  operate in fixed-frequency PWM mode. MODE pin = Low enables the power save mode with automatic transition from PFM mode to fixed-frequency PWM mode." - nice, but what is the mode when no mode pin is present?

- Martin

  • 0
    TI__Guru*** 142860 points
    Hi Martin,

    The IC operates in PFM/PWM mode only. This information should be in the comparison table on page 3. See the TPS62260 D/S for an example of how this would look.

    But this device is quite old. Do you need a leaded package? We have the new TLV62568 in a SOT-23 package and in a new SOT-563 package, which is smaller but still with leads. In QFN, we have the more efficient TPS62821.
  • 0 in reply to Chris Glaser
    Intellectual 400 points
    Hi Chris,

    I have the TLV62568 designed in and its power saving mode generates too much noise in my analog circuitry. So I am looking for something without this pulse-skipping mode. I was thinking about TPS62561 which in SOT runs in continuous PWM. I have the eval board here and the output looks nice. TPS62240 would have been nice as it is pin compatible to TLV62568 and wouldn't have required a redesign of the PCB.
    I could live with QFN packages, but if I have the choice I'd prefer leaded packages like SOT23-5 as I have the space and prototyping is just easier. Any better suggestion for replacing the TLV62568? I also have the LMR10510 eval board here - which has a bit an antique look with its huge capacitors (1206 or so) and National Semiconductor logo. Output at first glance also seemed not so clean.
    Input 5.5 V
    Output 2.1 V and 3.2 V (I need these two supplies)
    Current < 100 mA (typ. 40 mA)
    Low noise (no pulse skipping)

    Thanks, Martin
  • 0 in reply to Martin55843
    TI__Guru*** 142860 points
    Thanks for explaining.

    If you want to debug the issues with the power save mode, you can post some waveforms and your setup. Did you already use a feedforward cap to reduce the PFM ripple?

    TPS62561 is one option. There are also other options in the TLV62568/9 family that are pin to pin. Which package do you use? SOT-23 (5 or 6 pin) or SOT-563?
  • 0 in reply to Chris Glaser
    Intellectual 400 points
    I use the TLV62568DBV (SOT23-5). I did not try the feedforward C as I did not expect any fundamental changes. Which pin compatible version do you mean?

    - Martin
  • 0 in reply to Martin55843
    TI__Guru*** 142860 points
    Yes, the feedforward cap should reduce the magnitude of the ripple voltage under some conditions. See Figure 13 and 14 in the TLV62585 D/S.

    We will soon be sampling a forced PWM mode version of the TLV62568 and TLV62569, but this will be in the smaller SOT-563 package.
  • 0 in reply to Chris Glaser
    Intellectual 400 points

    FF C: I see - but it just increases the frequency of the intermittent mode by less than a factor of 2 - not enough to make a significant improvement.

    Regarding forced PWM versions of TLV62568: When will they be available? If we do a redesign, pinout and size would not matter, but for wiring them up manually for testing, a similar pin layout would be nice.

    Another enhancement request: Have identical pinout for similar function 5- or 6-pin package swichmode regulators...

    - Martin

  • 0 in reply to Martin55843
    TI__Guru*** 142860 points
    Hi Martin,

    The Cff also reduces the ripple magnitude. Is the lower frequency the issue in your system?

    The forced PWM devices should be sampling later this month.

    The 5 and 6 pin TLV62568 devices are pin to pin. The DRL package is much smaller and does not have the same orientation.

    Of course, you can order EVMs for any of these devices to test quickly without having to make a PCB of your own. I recommend this, instead of trying to wire in a different pinout device onto an existing PCB.
  • 0 in reply to Chris Glaser
    Intellectual 400 points
    The intermittent PWM mode frequency is much lower than the switching frequency and as I am filtering the output with an LC filter, attenuation is much lower. I also had the problem that filter damping had an error in the schematic, so there was some resonance effect (which is now solved).

    How do I get hold of the forced PWM samples? Do they get a new part number?
    I agree on the EVM. On the other hand, wiring up a SOT-23 with some microscope acrobatics is also feasible, just not in volume production...

    - Martin
  • 0 in reply to Martin55843
    TI__Guru*** 142860 points
    The forced PWM versions will have an 'A' at the end of the part number and will be sample-able on the web, when they are ready to sample.
  • 0 in reply to Chris Glaser
    Intellectual 400 points

    Do you have any indication when roughly to look for those? Or can I set up a notification somehow? I'd like to avoid looking daily when we are talking Q3 or so...

    - Martin

  • 0 in reply to Martin55843
    TI__Guru*** 142860 points
    I expect them to be on the web at the end of April.
  • 0 in reply to Chris Glaser
    TI__Guru*** 142860 points
    Hi Martin,

    The product folder and D/S are ready here: www.ti.com/.../TLV62568A The samples should be requestable from that page with a week or two.