Maximum Current Drive Strength for PXIe-6570/PXIe-6571 and PXIe-6535

Issue Details

What can happen to the module if I make it drive more than in the specifications?

I realized that the channels of the module can't drive more than ±32mA but noticed in tests that it can drive more, how should we explain that PXIe-6570/PXIe-6571 can drive up to 60mA?

Solution

While capable of temporarily producing drive strengths of over the specified 32 mA maximum, PXIe-657x and PXIe-6535 risk two main failure modes when operated beyond specifications: DC Accuracy and Long-Term Reliability.

DC Accuracy
1. With a higher DC driver output current, we should expect higher deviations from the nominal voltage. 

2. The nominal voltage must account for the PXIe-657x internal parasitic resistances of ~ 1 Ω in addition to any cable or fixture resistances in the hardware setup.

Note: The PXIe-657x DC Accuracy driver specification of ±15 mV is warranted for a 1 MΩ load termination only.

Long-Term Reliability
1. Due to overheating on the pin electronics backend, there are long-term reliability concerns for higher DC drive currents.

2. To include the PXIe-657x operation in different corner cases, the specification was set to a maximum DC Drive Current of +/- 32 mA to ensure long-term reliability for our customers.

3. The recommendation is to stay under the limits (±16mA and ±32 mA depending on the voltage level and module) to ensure the module’s specified performance and long-term reliability under different operating conditions.