LTC2057/LTC2057HV unwanted-voltage spike problem

Question

Hello, 
 
 I've found a strange voltage-spike at start-up around 80&micro;s when simulating the LTC2057HV and LTC2057. 
 I run a similar simulation for ADA4077 and I've not seen this type of spike. 
 Can you please tell me why this happens? is it becasue of zero-drift start-up? 
 How can I cope with that? any suggestion from your sie is very helpful. 
 In the attachment you will find the simulation files. 
 
 Thank you for your time and consideration! 
 2402.LTC2057HV_Behaviour.zip

PaulCA · Accepted Answer

Hello mehdiaghayi , We will contact the product owner regarding this issue and get back to you. Thanks! Best regards, Paul)

ahalyab · Answer

Hi mehdiaghayi , I was able to resolve the issue by changing certain parameters in your simulation file: 
 
 Change Vop_n to -7V DC and Vop to +7V DC 
 Remove "startup" and "uic" from your .tran command 
 
 The startup command is used to simulate an initial condition of having the voltage sources turned off and then ramp up to their full value in about 20us. However, using the startup command can cause transient spikes in the output voltage. Transient behavior during a power-on or power-off condition is expected and is usually defined in the part's datasheet. 
 Both ADA4077 and LTC2057/HV have these transient spikes, it's just that ADA4077 has a much smaller spike than LTC2057 (if you zoom into your LTspice sim, you will be able to see the transient spike on ADA4077 as well). Both parts datasheets have TPC graphs on the startup and shutdown transient behavior - LTC2057/HV shows these graphs on Pg 11 of the DS while ADA4077 shows these graphs on Pg 15-16. I hope this helps! Let me know if you have any more questions. 
 Regards, 
 Ahalya Bhandarkar

mehdiaghayi · Answer

Hi Ahalya, 
 It's very good that in practical experiment I'll not see such a transient of about 3V. I've changed my simulation data based on your suggestions and get a better waveform. 
 
 Thank you so much for your informative answer. 
 Regards, 
 Mehdiaghayi

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LTC2057/LTC2057HV unwanted-voltage spike problem