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TLV2365: Simulation with XTLV2365 for DC-IRIS motor control application

Praneeta Jain
Prodigy 30 points
Part Number: TLV2365
Other Parts Discussed in Thread: LMH6642, TLV365
We have an Op-Amp-based DC-IRIS control circuit in our security IP camera project. This circuit has been validated to work with LMH6642MF/NOPB and LMH6643MA/NOPB Op-Amp ICs where the IRIS functionality is properly working. Please find the schematic (Old) for your reference.
As per the recent conversation between TI and VVDN, and your suggestions, we have replaced the LMH6643MA/NOPB with XTLV2365 and LMH6642MF/NOPB with TLV365DBV as these new parts are a direct replacement of the original part.
Original New (Alternate)
LMH6643MA/NOPB
XTLV2365 
LMH6642MF/NOPB
TLV365DBV
With these new parts, we are facing issues in the DC IRIS operation. The IRIS motor is working in only one direction (Open to Close direction) and not working in the other direction. All other Hardware and Software setup is the same as earlier. I have attached the schematic with new parts for your reference.
Please let us know if there is any relevant difference between the two Op-Amps and whether any separate tuning change is required for the new parts to make this circuit work. 
  • 0
    TI__Genius 16996 points

    Hello Praneeta,

    I can work to assist with this project.  Could you confirm your gain settings for both amplifier stages, as well as the characteristics of your input signals, output loading, and power supply (VIRIS)?

    The gain-bandwidth product of the TLV365 (50 MHz)  is lower than the LMH6642 (57MHz), but both parts are voltage-feedback op-amps and should operate similarly to each other.

    Could you explain more about the IRIS motor only working in one direction?

    Best,

    Alec

  • +1 in reply to Alec Saebeler
    Prodigy 30 points

    Hi Alec,

    Sorry for the delayed response,

    I will just give a brief for this circuit and the testing we have done till now,

    Through this circuit, we are trying to run the DC motor and that will work in one direction only U16 IC is just working as a buffer and there is no issue due to U16 we have checked that, the U5 IC is working as an op-amp voltage comparator and we are facing the issue due to this IC only, this may be due to reason TLV365DBV operating time is more than LMH6642MF/NOPB so it is not able to respond as per our existing setting. power supply (VIRIS) is 3.3V.

    Today we have done one iteration and were able to find one solution, we tried placing 0.1uF on the R55 Resistor Pad as shown in the attached image and Now IRIS is working properly the same as the OLD design.

    Can you please see and tell us what exact parameter of Op-amp is causing the issue?

  • 0 in reply to Praneeta Jain
    TI__Genius 11060 points

    Hello Praneeta,

    This is a very interesting fix to the circuit. The major difference between these devices is the bandwidth and slew rate of the devices as most of the other specs are similar. Is there any information you can give as to why this capacitor was placed in this location or if there were other spots that also worked when adjusting the circuit?

    Best Regards,

    Ignacio