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Unexpected behavior of LT1014 at low temperature

BIPIN KUMAR
Prodigy 20 points
Other Parts Discussed in Thread: LT1014

I am using LT1014 IC in a closed loop servo electronics to drive a load of maximum 8mA current. When I am testing this interface at low temperature especially below -15 deg Celsius, this interface output is showing a ripple of 1 Vrms, 60-110KHz. The same interface doesn't show any anomaly or ripple with AD713.

What may be the reason?

  • 0
    TI__Guru**** 166116 points

    Bipin Kumar,

    Have you tested your loop for gain and phase margin?
    I suspect the loop may be marginally stable and minor performance changes in the op-amp and passive components pushed the loop into the unstable region.

    Is the oscillation waveform sinusoidal, saw-tooth, or some other waveform?

  • 0 in reply to Ron Michallick
    Prodigy 20 points

    Dear Ron Michallick

    Thanks a lot for your response. I have not tested it for gain margin & phase margin. This observation is seen while carrying out functionality test of drive circuitry

    with 1.2K Load at -40 deg. Deviation ( A ripple of 1 Vrms, 70-110 KHz Sinusoidal Waveform) is not seen whenever either internal temp of box is less than -15 deg or  with AD713 IC.

    What parameters of LT1014 can create (which is not dominant in AD713) this kind of temperature dependent behavior?

    Bipin

  • 0 in reply to BIPIN KUMAR
    TI__Guru**** 166116 points
    Bipin,

    All parameters change with temperature; most change very little. If the loop is marginally stable at 25C, any change can seem large.
    AD713 has a larger bandwidth and slew rate which is less phase lag. This make the loop frequency compensation more important. these are the passive components in the feedback loops.