This thread has been locked.
If you have a related question, please click the "Ask a related question" button in the top right corner. The newly created question will be automatically linked to this question.
Part Number: OPA2348
My customer using OPA2348 to monitor the NTC sensor which is integrated on IGBT module. the input voltage of IN+ is range from1.8V~3.7V. the VCC of OPA2348 is +5V.
Normally, the IN- (connect to Output via a IN4148) will follow the inputs, but sometimes the IN-(connect to Output via a IN4148) is 0.7V. It may happen when testing for days, sometimes is 10 days.
is there any risk of using the below schematic? thanks!
The full schematic as below:
We are glad that we were able to resolve this issue, and will now proceed to close this thread.
If you have further questions related to this thread, you may click "Ask a related question" below. The newly created question will be automatically linked to this question.
In reply to Gavin Jiang:
I believe the problem you see is caused by the back-to-back input protection diodes between the input terminals of OPA2171 - see below.
In order to eliminate the issue, please use instead OPA2196 or OPA2191, which do not include those input diodes - see below.
Marek Lis, MGTSSr Application EngineerPrecision Analog - TI Tucson
In reply to Marek Lis:
Regards,Ronald MichallickLinear Applications
TI assumes no liability for applications assistance or customer product design. Customer is fully responsible for all design decisions and engineering with regard to its products, including decisions relating to application of TI products. By providing technical information, TI does not intend to offer or provide engineering services or advice concerning Customer's design. If Customer desires engineering services, the Customer should rely on its retained employees and consultants and/or procure engineering services from a licensed professional engineer (LPE).
OPA2348 does not have back-to-back input protection diodes but the diodes from OPA2171 still may effect its output-see below.
With all the capacitance around the inputs, the circuit gets into a lock-up state, which gets reset by discharging the cap with the multi-meter.
The circuit is called a half-wave recifier because when the output is loaded in a way to require output current sinking, it will only show positive half of the input waveforem - see below.
I have simulated the circuit for various values of C1 and the results are shown above. What it means is that depending on R1*C1 time constant, the output will have dramatically different shape, which results in a large differential voltage between the inputs of OPA348 – see above. The output will eventually snap back to follow the input but for a large values of C1like 100nF, it may limit the frequency below 1kHz (10k||100nF => 1ms).
All content and materials on this site are provided "as is". TI and its respective suppliers and providers of content make no representations about the suitability of these materials for any purpose and disclaim all warranties and conditions with regard to these materials, including but not limited to all implied warranties and conditions of merchantability, fitness for a particular purpose, title and non-infringement of any third party intellectual property right. No license, either express or implied, by estoppel or otherwise, is granted by TI. Use of the information on this site may require a license from a third party, or a license from TI.
TI is a global semiconductor design and manufacturing company. Innovate with 100,000+ analog ICs andembedded processors, along with software, tools and the industry’s largest sales/support staff.