US 6,650,154 B2Granted

Starter circuit

AssigneeFujitsu Limited

InventorYoshiaki Okuyama

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Abstract

A voltage generating unit includes first resistors and a first transistor connected in series between first and second power supply lines. Since the gate of the first transistor is constantly supplied with a voltage higher than its drain voltage, the rise of a first voltage of a first node is gentle compared to that in the conventional art. A starter signal generating unit generates, according to the first voltage, a second voltage at a second node connecting a second resistor with a second transistor. The timing of reversing the logic level of the second voltage is delayed compared to that in the conventional art. Therefore, the time period from power-up until output of a starter signal is longer than in the conventional art. Consequently, even when the power supply voltage is low, the time period required to initialize an internal circuit is ensured, thereby initializing the internal circuit without fail.

Claims1

Dependent claims

A starter circuit comprising:

a voltage generating unit, including a first resistor, a second resistor, a third resistor, and a first transistor, connected in series between a first power supply line and a second power supply line, said first transistor being connected at its gate to a connection node of said second and third resistors, and said voltage generating unit generating a first voltage at a first node where resistive division is made by said first and second resistors;
a starter signal generating unit including a fourth resistor and a second transistor having its gate connected to said first node, connected in series between said first power supply line and said second power supply line, which generates a second voltage at a second node connecting said fourth resistor with said second transistor;
and
a waveform shaping unit for shaping a waveform of the voltage of said second node and outputting the shape waveform as a starter signal that initializes an internal circuit of an integrated circuit.

1 more element

Dependencies are inferred from the claim text.