US 8,525,574 B1Granted

Bootstrap switch circuit with over-voltage prevention

AssigneeLSI Corporation

InventorAbhishek Duggal

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Abstract

In one embodiment, a bootstrap switch circuit has (i) a switch device that selectively provides a input signal as an output signal and bootstrap circuitry that provides a relatively high-voltage control signal to the gate of the switch device to turn on the switch device while preventing any over-voltage conditions from being applied to the switch device. The bootstrap circuitry includes a capacitor and a number of transistors configured as either switches or inverters. The circuit has two operating phases: one in which the capacitor gets charged while the switch device is turned off and the other in which the charged capacitor is isolated and used to generate the high-voltage control signal to be a fixed voltage difference above the current voltage level of the input signal applied to the switch device, thereby preventing an over-voltage condition.

Claims22

Dependent claims

Apparatus having a bootstrap switch circuit comprising:

a switch device connected between an input node and an output node;
a first capacitor connected between the input node and a gate of the switch device;
and
bootstrap circuitry selectively interconnecting a first plate of the first capacitor to the gate of the switch device and a second plate of the first capacitor to the input node, wherein:
during a first phase, the bootstrap circuitry is configured to (i) turn off the switch device and (ii) charge the first capacitor to a pre-charge voltage level which is no higher than a supply voltage level;
during a second phase, the bootstrap circuitry is configured to (i) cease charging the first capacitor and (ii) connect the first capacitor between the input node and the gate of the switch device, such that a voltage difference between the gate and a channel node of the switch device is maintained at or below a voltage tolerance level for the switch device;
and
the bootstrap circuitry comprises:
a first switch connected between a first supply voltage node and the first plate of the first capacitor, wherein a gate of the first switch is connected to the gate of the switch device;
a second switch connected between the second plate of the first capacitor and a second supply voltage node;
a third switch connected between the second plate of the first capacitor and the input node;
a first inverter connected between the first supply voltage node and the second plate of the first capacitor;
and
a second inverter connected to an output signal of the first inverter and connected between the first and second plates of the first capacitor, wherein an output signal of the second inverter is connected to the gate of the switch device.

11 more elements

Apparatus having a bootstrap switch circuit comprising:

a thick-oxide switch device connected between an input node and an output node;
a first capacitor connected between the input node and a gate of the switch device;
and
bootstrap circuitry selectively interconnecting a first plate of the first capacitor to the gate of the switch device and a second plate of the first capacitor to the input node, wherein:
during a first phase, the bootstrap circuitry is configured to (i) turn off the switch device and (ii) charge the first capacitor to a pre-charge voltage level which is no higher than a supply voltage level;
during a second phase, the bootstrap circuitry is configured to (i) cease charging the first capacitor and (ii) connect the first capacitor between the input node and the gate of the switch device, such that a voltage difference between the gate and a channel node of the switch device is maintained at or below a voltage tolerance level for the switch device;
and
the bootstrap circuitry comprises one or more thin-oxide devices having gate oxide thinner than gate oxide of the thick-oxide switch device, wherein the bootstrap circuitry comprises:
a first switch connected between a first supply voltage node and the first plate of the first capacitor, wherein a gate of the first switch is connected to the gate of the switch device;
a second switch connected between the second plate of the first capacitor and a second supply voltage node;
a third switch connected between the second plate of the first capacitor and the input node;
a first inverter connected between the first supply voltage node and the second plate of the first capacitor;
a second inverter connected to an output signal of the first inverter and connected between the first and second plates of the first capacitor, wherein an output signal of the second inverter is connected to the gate of the switch device;
a fourth switch and a second capacitor connected in series between the first supply voltage node and the output signal of the second inverter;
a fifth switch and a sixth switch connected in series between the first supply voltage node and the output signal of the second inverter;
and
a third inverter connected between the two plates of the second capacitor and having an output signal connected to the gate of the switch device.

14 more elements

Dependencies are inferred from the claim text.

Facts

Application: 13/471,659Filed 15 May 2012
Granted: 3 Sep 2013
Term ends: Not estimatedThe source records don’t support an estimate.

Classification6 codes

H03K 17/063
Modifications for ensuring a fully conducting state: in field-effect transistor switches
G11C 27/02
Electric analogue stores, e.g. for storing instantaneous values: sample-and-hold arrangements
H03K 17/102
Modifications for increasing the maximum permissible switched voltage: in field-effect transistor switches
H03K 2217/0054
Indexing scheme related to electronic switching or gating, i.e. not by contact-making or -breaking covered by H03K17/00: gating switches, e.g.…