Operating the LT6106 above 36V

Thank you for your question. I am not an engineer, so I am unable to provide additional technical guidance. However, I found the information below, which may help answer your question: 

You cannot rely on the LT6106 for a 40 V supply when its  pin is tied directly to that 40 V rail, because 40 V is above the specified operating supply range of 2.7 V to 36 V. The 36 V limit is the top of the guaranteed operating range for ; all electrical specifications are only guaranteed up to this value. [1][2][3]

The “2.7 V to 44 V input voltage range” phrase refers to the allowable common‑mode (sense) voltage and matches the 44 V absolute maximum rating on –; it does not redefine the normal supply operating range. Practically, the device can tolerate up to 44 V on the monitored line from a survival standpoint, but operation between 36 V and 44 V is not characterized or guaranteed. [1][2][4]

For your 40 V rail, either:

• Keep using LT6106 but power  from a lower regulated/derived voltage (≤36 V) while sensing the 40 V line within the allowed common‑mode range, or
• Choose a current‑sense amplifier whose specified supply range includes 40 V.

You may also find these references helpful:

Thank you!  This was very helpful.  We ended up going with the LTC6101 as a direct replacement.