Power-on detecting circuit

A circuit for detecting a power-on voltage of a power supply, comprising:

• a voltage divider connected between a first power supply and a second power supply, the potential of the second power supply is lower than the potential of the first power supply, the voltage divider including a series circuit which includes:
• a diode-connected first pMOS transistor;
• a first dividing resistor connected to the first pMOS transistor;
• and
• a second dividing resistor connected between the first dividing resistor and the second power supply;
• and
• a detecting circuit connected between the first power supply and the second power supply, the detecting circuit including:
• a second pMOS transistor whose gate electrode is connected to a connection node between the first dividing resistor and the second dividing resistor;
• and
• a drain resistor connected to the drain electrode of the second pMOS transistor and the second power supply,
• wherein a resistance value R1 of the first dividing resistor and a resistance value R2 of the second dividing resistor satisfy:
• |dVGS1/dT|×R2/(R1+R2)=|dVGS2/dT|
• where dVGS1/dT is a temperature dependence of gate-source voltage of the first pMOS transistor, and dVGS2/dT is a temperature dependence of gate-source voltage of the second pMOS transistor.

A circuit for detecting a power-on voltage of power supply, comprising:

• a voltage divider connected between a first power supply and a second power supply, the potential of the second power supply is lower than the potential of the first power supply, the voltage divider including a series circuit comprising:
• a diode-connected first divider pMOS transistor;
• a diode-connected second divider pMOS transistor connected to the first divider pMOS transistor;
• a first dividing resistor connected to the second divider pMOS transistor;
• and
• a second dividing resistor connected between the first dividing resistor and the second power supply;
• and
• a detecting circuit connected between the first power supply and the second power supply, the detecting circuit including:
• a detecting pMOS transistor whose gate electrode is connected to a connection node between the first dividing resistor and the second dividing resistor;
• a source resistor connected between the first power supply and the source electrode of the detecting pMOS transistor;
• and
• a drain resistor connected to the drain electrode of the detecting pMOS transistor and the second power supply
• wherein, with gate width W and gate length L, ratios W/L in the first and second divider pMOS transistors are equal,
• wherein resistance values of the first and second dividing resistors are equal.

A circuit for detecting a power-on voltage of a power supply, comprising:

• a voltage divider connected between a first power supply and a second power supply, the potential of the second power supply is lower than the potential of the first power supply, the voltage divider including a series circuit comprising:
• a diode-connected first divider pMOS transistor;
• a diode-connected second divider pMOS transistor connected to the first divider pMOS transistor;
• a first dividing resistor connected to the second divider pMOS transistor;
• and
• a second dividing resistor connected between the first dividing resistor and the second power supply;
• and
• a detecting circuit connected between the first power supply and the second power supply, the detecting circuit including:
• a detecting pMOS transistor whose gate electrode is connected to a connection node between the first dividing resistor and the second dividing resistor;
• a source resistor connected between the first power supply and the source electrode of the detecting pMOS transistor;
• and
• a drain resistor connected to the drain electrode of the detecting pMOS transistor and the second power supply,
• wherein a relationship given by:
• Vdd−{Vdd−|VGS1|−|VGS2|}/2=|VGS3|
• is satisfied, where Vdd is a potential supplied by the first power supply, VGS1 is a gate-source voltage of the first divider pMOS transistor, VGS2 is a gate-source voltage of the second divider pMOS transistor and VGS3 is a gate-source voltage of the detecting pMOS transistor.