Part Number: INA826
i am developing an constant current source. The following picture shows the concept.
The current is given by dividing the DA-Converter-Voltage with one of the resistor values (SHUNTS). Which resistor is activated is controlled by an microcontroller. Also the DA-Voltage ist controlled by the microcontroller. The Current flows through P$1. The INA826 has a supply voltage of 30 V DC, Rg is not connected, so the gain is 1. Pin 4 of the INA826 is allways connected to 30V. Pin 1 varies between 28 and 30 V. That means the maximum output voltage is 2 V.
Now the Problem: The INA826 gets allways damaged. I cant explain why. I tried other Instrumentation Amplifiers from other companies at the same conditions and it worked fine. Also I tried the INA828 and it gets damaged too. As soon as voltage is turned on, the INA826 blows. I damaged allmost 10 devices.
Is something wrong with the wiring of the INA826?
Precision Amplifier Applications - TI Tucson
In reply to Alexander Davis:
I dont think that the inputs are the problems. The data sheet says that they are protected up to 40 V. I tried the resistor in series to the inputs before.
There were some moments when the circuit works like expected with the INA826. But that didnt work long. After a day I turned the circuit on in got damaged again. I also tried to work only with the INA826 and test it. First it worked fine but after a time it just blows, without doing something.
The device gets really hot and starts to smoke.
In reply to Peter Simon Terentschenko:
That's a pretty catastrophic failure. While it's possible that there's an issue with the PCB, I think that's unlikely, since it does work sometimes. What I suspect is more likely is a latchup event, possibly being caused by the power supply itself. If the power supply overshoots above the INA826's max supply voltage, it's possible it could be triggering an ESD structure which then latches on until the amplifier is destroyed. To eliminate that possibility, you could add an appropriately rated TVS diode (say 33V or so, depending on your typical supply voltages) across the supply pins of the INA826. That would act as a first line of defense and clamp the supply before damage to the INA826 occurred.
On a second look at the schematic, it's possible that at low current levels, you may be violating both the input common mode range and output swing capabilities of the INA826, but without knowing your current ranges, I can't say for sure.
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. 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 respect to these materials. 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.