§12A-1-208.

§12A-1-208.
   
   A term providing that one party or his successor in interest may
   accelerate payment or performance or require collateral or additional
   collateral "at will" or "when he deems himself insecure" or in words
   of similar import shall be construed to mean that he shall have power
   to do so only if he in good faith believes that the prospect of
   payment or performance is impaired. The burden of establishing lack of
   good faith is on the party against whom the power has been exercised.