Vref Delta and Post Radiation Data

Hi Steve,

Thanks for reaching out. Here are a few answers I can provide:

1. The post-radiation min/max values in the datasheet are referring to Total Ionizing Dose (TID) radiation specifically. Since TID effects are accumulated over time, there is no large immediate change. However, you can see how much the typical reference voltage shifts across TID in Figure 16 from the datasheet. The orderable device you will be using (5962R0722962VZA) is rated for Low Dose Rate TID, which was accumulated at 10 mrad/s during testing. The time needed to accumulate a given level of TID can be calculated using the accumulation rate.

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2. The Delta parameters listed in the datasheet are meant to indicate parameter shift due to aging effects (Group C, life test). These values are measured at 25°C and do no include any radiation effects. 

Hop

Hope this helps.

Thanks,

Sarah

Hi Steve,

Great, I’m glad this is helpful. Here are a few more comments on your follow-up questions:

1. “Biased” means that the device is powered, whereas “unbiased” means that all of the pins are grounded to mimic being in a standby state. Both tests are performed to ensure that any susceptibility a technology may have to radiation under either condition is characterized. For this device, “biased” testing was done with VI=60V.

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2. The electrical characteristics table is meant to provide a range of min/max values that each parameter will fall within, while the figures are meant to show how the typical value of a parameter will shift due to a particular variable (such as TID in Figure 16 or temperature in Figure 8). Each parameter in the table has a distribution curve of values that it may take, with the "typical" (or "nominal") value being most common and the mix/max values being cutoffs that are used during post-manufacturing screening of the parts. The min/max range from the table encompasses variation caused by part-to-part manufacturing differences, temperature (-55 °C to 125 °C, or subsets of this range as stated by the subgroups column), and any electrical conditions stated in the table’s test conditions. There is also some guardbanding added on top of this when determining the min/max range as a buffer to ensure that parameters fall within spec.

As seen in the figure, the typical value of the reference voltage shifts with TID and thus the post-radiation maximum value given by the table also shifts in order to accommodate for the other sources of variation. As you noted, the worst-case shift occurs for this device when it is unbiased. Ensuring the device is biased would allow you to avoid the worst-case scenario for reference voltage shift caused by TID, but it is difficult to give an exact maximum value for this condition since the table only accounts for the worst-case (unbiased) scenario. An approximation could be made using the information from the figures and the conditions you expect for your application.

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I know this is a fairly wordy response, so please let me know if there is anything I can further clarify.

Thanks,

Sarah

Hi Steve,

Here is the TID data for Vref provided by the radiation team. We are working on making the full report for this device available on its web page.

For these tests Vref did not exceed 1.31842 V, which is well below the ensured datasheet maximum of 1.45 V. Hopefully this is helpful with regards to your reference voltage tolerance goals.

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For the bias tests, the input pin was held at 15 V, while the output and adjust pins were connected through resistors to -15 V so that the load current was minimized to prevent internal heating of the device and possible self annealing. For the unbiased condition, all pins were grounded.

HDR for these tests: 34-39 rad(Si)/s

LDR for these tests: 10 mrad(Si)/s

Sample size: LDR biased testing used 15 devices, LDR unbiased testing used 15 devices, HDR biased testing used 18 devices, and HDR unbiased testing used 15 devices. 

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Thanks,

Sarah