Semiconductor integrated circuit with voltage generation circuit, liquid crystal display controller and mobile electric equipment
View Patent ↗There is to be provided a liquid crystal drive controller with a built-in power supply circuit wherein latch-up is made difficult to arise even if one amplitude level of the segment line drive voltage is set to the ground potential and the levels of other liquid crystal drive voltages are determined accordingly. A semiconductor integrated circuit with a built-in power supply circuit, wherein a negative voltage generated in a power supply circuit is applied to a substrate or a well region as a bias voltage, is provided with a switch for temporarily applying the ground potential to the substrate or well region to be biased with the negative voltage at the time of starting up the power supply circuit.
1. A semiconductor integrated circuit having built-in power supply circuit which, receiving an external source voltage, generates a positive voltage higher than the external source voltage and a negative voltage lower than a ground potential, the semiconductor integrated circuit comprising:
a switch element connected between a first wiring for feeding the negative voltage as a bias voltage for a substrate and a second wiring for supplying the ground potential.
2. The semiconductor integrated circuit according to claim 1 , wherein the switch element is temporarily made to conduct at a time of starting up the built-in power supply circuit to set potential of the substrate, to which the negative voltage is to be applied, temporarily to the ground potential.
3. The semiconductor integrated circuit according to claim 2 , further comprising:
a reset circuit for generating a control signal to make the switch element conduct temporarily in accordance with another control signal for starting up the built-in power supply circuit.
4. The semiconductor integrated circuit according to claim 1 , wherein the switch element is comprised of a high voltage withstand MOSFET.
5. The semiconductor integrated circuit according to claim 1 ,
wherein the substrate is a semiconductor substrate of a first conductivity type,
wherein the semiconductor integrated circuit includes:
a first MOSFET of a first channel type having a source region of a second conductivity type different from the first conductivity type and a drain region of the second conductivity type, both of which are formed in the semiconductor substrate of the first conductivity type.
6. The semiconductor integrated circuit according to claim 5 , wherein the semiconductor integrated circuit further includes:
a first well region of the second conductivity type formed in the semiconductor substrate of the first conductivity type, and
a second MOSFET of a second channel type having a source region of the first conductivity type and a drain region of the first conductivity type and a drain region of the first conductivity type, both of which are formed in the first well region.
7. The semiconductor integrated circuit according to claim 6 , wherein the semiconductor integrated circuit further includes:
a second well region of the second conductivity type formed in the semiconductor substrate of the first conductivity type,
a third MOSFET of the second channel type having a source region of the first conductivity type and a drain region of the first conductivity type, both of which are formed in the third well region,
a third well region of the first conductivity type formed in the second well region, and
a forth MOSFET of the first channel type having a source region of the second conductivity type and a drain region of the second conductivity type, both of which are formed in the third well region.