Hello,
I used to employ the LMV824PWR from TI on the following Multiple Feedback Bandpass filter :
NB : the other 3 gates of the circuit are used as follower.
As the LMV824PWR from TI is now obsolete, I replaced it by the LMV824MTX from NS.
Unfortunately, the ESD capabilité of my product decreased of 5kV (contact discharges), (6kV for the LMV824 PWR (TI) to 1kV with the LMV824MTX (NS)).
When equipped with the LMV824PWR from TI, my product fails at 6kV (without problems on the LMV824)
When equipped with the LMV824MTX from NS, my product fails at 1kV : the 4 outputs of the circuit are all "locked" to 30mV, and a switch off of the power supply is needed to get out of this lock.
I clearly identifie that filter circuit was responsible of this phenomenon but I don't find the solution.
All this tries was not able to eliminate the problem :
-add a resistor of 50ohms in serie on the output (the ouput of the filter is directly connected follower circuit);
-add a resistor of 1kohms on the output for charging;
-add clamping diode on both inputs and output in order to limit signals between GND and VCC.
When I connect a second bypass capacitor of 1µF (the first one is 100nF) and C139 = 1µF, the ESD threshold increase to 3kV.
Can anybody tell me the difference between LMV824PWR and LMV824MTX regarding the ESD internal protection ?
What is the phenomenon where the circuit locks all its output ?
Thank you in advance for your help.
JDM