High SRAM Low Power Mode Current

Summary:

Low power mode current is a very important parameter of most microcontrollers due to increasing battery powered applications. A new microcontroller had high current issues with certain SRAM modules which were produced using a new memory compiler. All devices were measuring 100’s µA of low power mode current which was two orders of magnitude higher that the requirement. The SRAM instances could be power gated in this design. The high current issue disappeared when all SRAM were power gated off; therefore, it was known that the high quiescent current was being consumed inside the SRAM. Many FA techniques had to be used to determine the root cause: OBIRCh, light emission, microprobing, and nanoprobe device characterization. In addition, analysis had to be performed from both the front and back of the die.