INA326: High Temperature Equivalent

Hi Harris,

Q: The INA device will be used in environment of 200C operating temperature. 

Can you explain what do you mean by 200C operating temperature? Do you mean that RTD will measure the changes in temperature up to 200C? or Do you mean that INAxxx IC will operate at 200C temperature environment.

Our max. junction temperature of all INAxxx is rated at 150C. If the operating environment is actually 200C, you have to use cooling block or other means to cool the entire circuit at approx. 80C. 

https://e2e.ti.com/support/amplifiers/f/14/t/818894

We have a wide selection of instrumentation amplifiers. Please specify what you are meant by "closet match" - supply voltage, offset voltage, operating temperature, bias current, noise, drift etc.. Once we have the key requirements, we can help you to find the latest INAxxx part for your application.  

Best,

Raymond

Hi Raymond,

Currently i am designing a circuit to measure RTD value. However the circuit board is expose to 200C temperature which means that i need a op amp that can operate up to 200C operating temperature. In the reference design (TIDU969) it uses INA326 (but its operating temperature is only 80C max), and when i replaced it with INA333-HT it does not work as well as INA326, such as the gain is setting can never reach what it is stated in the datasheet. Perhaps i am missing something in the design that you can advice ?. Thanks.

Regards,

Harris

Hi Harris,

Here is the issues: TIDU969 schematic shown that the RTD to voltage reference design with Gain = 2(698k/2k)=698 V/V, see the image below. The part is not designed to operate at high temperature. Max. operating temperature is probably around 100C in the reference design, if properly cooling is taken place. 

With INA333-HT, the part may operate at ambient temperature at 200C, but the circuit gain has to be greater than > 100 V/V, see note 7 in the datasheet. If you implement the same circuit as TIDU969, what are other components ratings on the PCB board? The junction temperature of INA333 is rated 210C, and the application is operating at 200C, there is very little thermal margin for the part to operate properly. You need to find a way to cool the part in some ways. 

Please provide us some information about your RTD to Voltage measurement. 

1. The PCB is exposed to 200C, what is air temperature surround the PCB? Do you have cooler air in temperature in the vicinity. 

2. Are you able to place the PCB on a cooling block that could use to cool the components on the PCB? Of course, you have to pump cooling liquid and circulate the cooling block. It works like a car radiator to cool an engine. 

3. Can you use peltier cooler to cool INA326 or INA333-HT part, assume other components can operate at 200C? This will resemble some of CPU cooler for high performance gaming computer. In order to have the optimum IC performance, you have to cool the part. 

4. Please email us the RTD schematic and the PCB image with the installed setup. We need to find a way to cool the PCB. The actual operating temperature condition is too close to the max. rated thermal conditions by design in INA333-HT instrumentation amplifier. If we are able to cool efficiently, we may be able to use INA326 for the application. I do not think that we have an instrumentation amplifier that is capable to operate higher temperature than INA333-HT.

5. What is RTD measured temperature ranges from low to high?

This is a public forum. If you want to keep the application in private, please send me "friendship" request via E2E forum. Once we establish a communication link, we are able to communicate via E2E private messaging, and keep the image, conversation, schematic information etc. in private.

Best,

Raymond