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LT1014 Latch up

premchand chennupati
Prodigy 60 points
Other Parts Discussed in Thread: LT1014
we are using LT1014 op-amp as inverting amplifier. using single power supply (+5V)  VCC- terminal connected to GND
R1(input resistance)=19.21K and RF =3K
whiling testing observed
LT1014 op-amp inverting amplifier output was going below ground (~-0.6Vdc) for ~4 minutes and then recovering  at -40 deg C condition.
The input signal (-15V ) is applied before LT1014(op amp) power is applied
is create the latchup
how much negative input can connect to create the latch up issue?
  • 0
    TI__Guru*** 140136 points

    Premchand,

    What is the output voltage of the other three channels?

    Page 18 of data sheet says the phase inversion protection stops working if other amplifiers are driven low. 

  • 0 in reply to Ron Michallick
    Prodigy 60 points
    Hello Ronald

    Thanks a lot for quick reply

    we are using LT1014 op-amp-1 and opamp-4 as inverting amplifier and opamp-2, opamp-4 are unused.

    using single power supply (+5V) VCC- terminal connected to GND

    we are using op-amp-1 and op-amp-4 for monitoring -15V supply

    inverting amplifier op-amp-1=> R1(input resistance)==19.21K RF=>3.022K

    inverting amplifier op-amp-4=> R1(input resistance)==5.921K RF=>1.049K

    During power-up :The input signal (-15V ) is applied before LT1014(op amp) power(+5V) is applied


    From simulation : voltage at inverting terminal of opamp-1 is -2.1V
    voltage at inverting terminal of opamp-2 is -2.3V

    because of above condition the latch issues will occur?

    If BAS70 diode connected across the inverting terminal of op-amp-1 to GND is sufficient to Solve the latch up issue?

    or other diode for inverting terminal of op-amp-4 to GND diode need to connect to solve issues?
    i.e two diodes required to solve this issue?
  • 0 in reply to premchand chennupati
    TI__Guru*** 140136 points
    Prechand,

    Can you check the output voltage on the two unused amplifiers? Are the inputs left unconnected?
    The data suggests that only one input should be below ground at a time. I will have to order samples to try to replicate your results.
  • 0 in reply to Ron Michallick
    Prodigy 60 points
    Hello Ronald Michallick

    Thanks for your support

    Unused op-amps are two

    Op-amp-2 and op-amp-3

    connected as like buffer

    non inverting input connected to voltage divider (R1=4.99k and R2=4.99K ) supply voltage for resistor divider circuit is 5V (same as supply voltage of op-amp)

    i.e non inverting input voltage is 2.5V and output voltage is 2.5V for op-amp-2 and op-amp-3

    Note : Op-amp-2 and op-amp-3 output not connected any circuit


    we are using op-amp-1 and op-amp-4 for monitoring -15V supply (Over voltage and under voltage )

    inverting amplifier op-amp-1=> R1(input resistance)==19.21K RF=>3.022K

    inverting amplifier op-amp-4=> R1(input resistance)==5.921K RF=>1.049K

    op-amp -1 and op-amp -4 output connected to comparator input


    Thanks
    premchand