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LMZ21700 - Vout above Recommended Operating Conditions?

John Seaber
Prodigy 130 points
Other Parts Discussed in Thread: LMZ21700

Hi,

LMZ21700 is rated for 0.9 < Vout < 6.0 under "Recommended Operating Conditions". Using the datasheet feedback equation RFBT = RFBB x (VOUT/ 0.8 – 1), it's possible to achieve Vout = 7.1V using:

Vin = 11.7V
RFBT = 44.2k
RFBB = 348k

In practice, Vout deviates by about 10% from calculations. Aside from this error, performance seems to be well suited for my application. A 5V LDO with 2V dropout is more economical than operating LMZ21700 at 6V with a 5V LDO specified for lower dropout voltage. Noise performance matches full linear regulation peformance in this system.

What are the potential production consequences of operating LMZ21700's output voltage above recommended conditions? 

  • 0
    TI__Genius 16025 points
    Hi John,

    Anything over Abs Max violates the datasheet and no guarantee of operation. We spec the recommended operation values with tolerances in mind to keep a buffer from Abs Max.

    It is recommended you perform extensive environmental and unit testing before committing to production if you decide to step outside the recommended operating values.

    It would help to use 0.1% tolerance resistors to limit the resistor impedance drift over temperature.

    Thanks,
    Anston