US 6,208,197 B1 · Internal charge pump voltage limit control

Abstract

A charge pump limits the voltages at nodes internal to the charge pump to reduce the risk of junction breakdown in the charge pump. The charge pump includes a first pump circuit, a second pump circuit, a first clamp and a second clamp. The first clamp limits the voltage level of a well by providing a current path from the well to the output lead when the voltage level of the well reaches a first predetermined limit. The voltage level at a node from which charge is redistributed to the well is limited by the second clamp, which is configured to provide a conductive path from the node to the output lead when the voltage level of the node reaches a second predetermined limit. The pump circuits can each include a logic circuit that is configured, depending on the level of an external supply voltage, to reduce the rate at which the capacitor node is boosted when the external supply voltage is relatively high. The logic circuit can also vary the voltage difference between the capacitor node and the external supply voltage to decrease the relative voltage level at the capacitor node relative to the level of the external supply voltage. These features also help reduce the risk of junction breakdown in the charge pump.

Claims31

Dependent claims

A charge pump formed in and on a semiconductor substance, the charge pump comprising:

a first pump circuit having an output lead and having a first switch formed in and on a well, the well having a conductivity different from a conductivity of the substance, the first pump circuit being coupled to receive an external supply voltage, wherein the first pump circuit is configured to cause the output lead to have an output voltage with a level higher than the level of the external supply voltage, and wherein the first switch comprises a P-channel transistor formed in an N-well, the drain of the P-channel transistor of the first switch being coupled to the output lead;
a second pump circuit being coupled to receive the external supply voltage, wherein the second pump circuit is configured to cause the well to have a voltage lever equal to or higher than the level of the output voltage;
a first clamp circuit coupled to the output lead and to the well, wherein the first clamp circuit is configured to provide a current path from the well to the output lead when the voltage level of the well reaches a first predetermined threshold;
and
a second clamp circuit coupled to the output lead and to an internal node wherein the internal node is coupled to the second pump circuit, wherein the second pump circuit is configured to provide a current path from the internal node to the output lead when a voltage level of the internal node reaches a second predetermined threshold.

2 more elements

A charge pump formed in and on a semiconductor substrate having a first conductivity, the charge pump having a first operational mode and a second operational mode, the charge pump comprising:

an output lead;
a first node;
a first switch coupled to the output lead and the first node, the switch being formed in an on a well, the well being formed in the substrate with a second conductivity that is different from the first conductivity, wherein the first switch is configured to selectively form a conductive path between the first node and the output lead;
a supply bus connected to receive an external supply voltage, the external supply voltage having a level that is greater in magnitude during the second operational mode than in the first operational mode;
and
a first pump circuit coupled to the first node and the supply bus, wherein the first pump circuit is configured to selectively boost a voltage level at the first node to level that is greater in magnitude than the level of the external supply voltage, the first pump circuit being further configured to boost the voltage level at the first node at a first rate during the first operational mode and at a second rate during the second operational mode, the first rate being different from the second rate.

3 more elements

A charge pump formed in and on a semiconductor substrate having a first conductivity, the charge pump having a first operational mode and a second operational mode, the charge pump comprising:

an output lead;
a first node;
a first switch coupled to the output lead and the first node, the switch being formed in an on a well, the well having a second conductivity, the second conductivity being different from the first conductivity, wherein the first switch is configured to selectively form a conductive path between the first node and the output lead;
a supply bus connected to receive an external supply voltage, the external supply voltage having a level that is greater in magnitude during the second operational mode than in the first operational mode;
and
first pump means, coupled to the first node and the supply bus, for selectively boosting a voltage level at the first node to level that is greater in magnitude than that of the external supply voltage, wherein the first pump means is configured to boost the voltage level at the first node at a first rate during the first operational mode and at a second rate during the second operational mode, the first rate being different from the second rate.

3 more elements

Dependencies are inferred from the claim text.

Internal charge pump voltage limit control

Life of this patent

Internal charge pump voltage limit control

Life of this patent

Abstract

Claims31