Patent ID: 6836145
Filing Date: 2004-12-28
Classification: G11C,H02M,H03K

Abstract:
A programming circuit for selectively either isolating a circuit ground node from an external terminal of an integrated circuit or allowing a programming voltage to be coupled from the external terminal to the circuit ground node, the programming circuit comprising:an isolation device coupled between the external terminal and the circuit ground node, the isolation device having a first terminal coupled to the external terminal, a second terminal coupled to the circuit ground node, and control terminal, the isolation device being operable to couple the programming voltage applied to the external terminal to the circuit ground node as long as the absolute value of the voltage coupled to the circuit ground node is within a predetermined magnitude of a control voltage applied to the control terminal of the isolation device; and a charge pump circuit having a power input coupled to the external terminal and an output terminal coupled to the control terminal of the isolation device, the charge pump being coupled to receive the programming voltage applied to the external terminal and being operable in a program mode to increase the absolute value of the programming voltage in response to a program command signal to generate the control voltage, the charge pump circuit being operable in an isolation mode to generate as the control voltage a voltage having an absolute value that is substantially less than the absolute value of the programming voltage, the charge pump circuit comprising: a capacitive device having first and second terminals; a boosting circuit coupled to the first terminal of the capacitive device, the boosting circuit being operable to apply a voltage to the first terminal of the capacitive device that varies between first and second voltages; a first current path coupled between the external terminal and the second terminal of the capacitive device, the first current path allowing current to flow to or from the capacitive device to change the charge of the capacitive device in a first direction when the boosting circuit is applying the first voltage to the first terminal of the capacitive device: and a second current path coupled between the second terminal of the capacitive device and the control terminal of the isolation device, the second current path allowing current to or from the capacitive device to change the charge of the capacitive device in a second direction that is opposite the first direction when the boosting circuit is applying the second voltage to the first terminal of the capacitive device.