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LM46002: 2MHz switching frequency efficiency data

franziskus
Expert 8369 points
Part Number: LM46002
Other Parts Discussed in Thread: LM46001, LMR43620, LMR33620

Team,

do we have efficiency data for this device when using 2MHz switching frequency?

Here's my customers spec:

  • Vin = 8..32V
  • Vout = 5V
  • Iout = 1mA..500mA, but in failure cases up to 1.5A

They had planned with the 1A version (LM46001), but due to the failure case probably need to go to th 2A version.

Questions

  • Is it possible to use both devices with these specs at 2MHz?
    • I see that switching f decreases in light load condition
  • Is there a minimum current for the regulation to still work?
  • Anything else that needs to be considered?

Best regards

  • 0
    TI__Guru 73585 points

    Hello

    Although the device will function at a switching frequency of 2MHz, you will not get very good performance.

    The efficiency will be poor, compared to the lower switching frequencies. 

    Also, the device will not operate at full frequency over your entire input voltage range, because of the relatively large

    Ton-min and Toff-min of this device.

    As an example, if we use the typ/max values for the timing, the frequency will start to fold back at about 8.5Vin/10VIn at your

    low voltage end, and about 20Vin/15Vin at your high voltage end.

    The device will still regulate and operate correctly over your entire input range of 8V to 32V. 

    However, the switching frequency will automatically reduce at the approximate end points mentioned above.

    The device will regulate and operate correctly from 0A to full load.  However, the frequency will automatically

    reduce at the lighter loads.  At light loads, the output voltage will also show a small increase from the nominal value.

    This light load mode operation remains true regardless of the selected switching frequency.

    It may be best to select a lower switching frequency such as 1MHz or less.

    Alternatively, you may want to look at some of our more higher performance devices, such as the LMR43620 or LMR33620 or LM63625.

    Thanks