Product Reference
2–7
Power Requirements
The Little Board/486e CPU operates on +5VDC (±5%). The ±9V RS-232 voltages are generated on
board. The exact power requirement of the Little Board/486e CPU system depends on several
factors such as:
! Amount of installed DRAM
! Number of installed byte-wide memory devices
! Peripheral connections
! MiniModule products (if installed)
! Other expansion boards attached to the PC/104 bus
For example: AT keyboards draw power from the motherboard, and there can be some loading from
the serial and parallel ports. Consult the specif icat ions in Ch apter 3 for th e ba sic pow er
requirements of your model.
If a switching power supply is used it must regulate pro perly with the syste m load . Some swi tching
power supplies do not regulate properly unless they are lo aded to some minimu m valu e. If this i s
the case, consult the manufacturer for information regarding additional loading or use another
supply or another type of power source such as a linear supply, or batteries.
Backup Battery
With only the real-time clock drawing current, the backup battery on the Little Board/486e should
last 10 years. If it supplies only the clock, replace the battery every 10 years as a routine
maintenance procedure.
Cooling Requirements
Adequate airflow should be provided to maintain an ambient temperature at or below 70°C within
the case. For Extended Temperature Qualified products, the temperature must remain at or below
85°C. Little Board/486e CPU uses a 486DX/System Log ic Ch ip rate d at 3.3V to mini mize p ower
drain. In addition a heat sink is provided for the CPU. The majority of the current draw and heat
generated come from the:
! 486 CPU
! DRAM
! video controller
! 486DX/System Logic Chip