Semiconductor integrated circuit device having voltage regulating unit for variable internal power voltage level

Claim 1

A semiconductor integrated circuit device comprising: a) an internal power source unit operative to produce an internal power voltage level regulated to a variable reference voltage level; and b) a reference voltage generating unit operative to produce said variable reference voltage level, and comprising b-1) a preliminary reference voltage generator for producing a preliminary reference voltage level from an external power voltage level, b-2) a preliminary voltage regulator responsive to said preliminary reference voltage level for producing a primary reference voltage level, b-3) a secondary reference voltage generator responsive to an external controlling signal for producing a secondary reference voltage level and a threshold voltage level from said external power voltage level, b-4) a first main voltage regulator responsive to said primary reference voltage level for regulating said variable reference voltage level to said primary reference voltage level while said primary reference voltage level is higher than said threshold voltage level, b-5) a controller enabled with said external controlling signal, and operative to compare said primary reference voltage level with said threshold voltage level for producing an activation signal, b-6) a latching means shifted to a reset state with a reset signal, and latching said activation signal from said controller, and b-7) a second main voltage regulator activated with said activation signal supplied from said latching means, and responsive to said secondary reference signal for regulating said variable reference voltage level to said secondary reference voltage level after said primary reference voltage level becomes lower than said threshold voltage level.