Yes, this is possible. A couple of things that should be kept in mind:
- All peripherals would be limited to run at 1.8V.
- The internal regulator would not work at 1.8V.
- 1.8V Vddext not supported for Automotive grade models
- SCLK max = 100MHz @ 1.8V
Also, to be on the safe side, in order to use 1.8V chips, verify in the
processor’s data sheet (electrical specifications) that the processor is able
to have an output low voltage (maximum) as dictated by the SDRAM device data
There is an EE-Note: Using Blackfin Processor Hibernate State for Low Standby
Power (EE-334) that discusses a solution using mobile SDRAM at 1.8V. Also,
Blackfin Processor and SDRAM Technology (EE-326) briefly discusses this topic.
Both EE-Notes can be downloaded from www.analog.com/ee-notes