Abstract: A negative charge pump circuit is disclosed. The pump circuit includes several stages, each stage including a switching transistor, a pull up diode, and a pull down diode. The pump circuit also includes a blocking transistor coupled between the gate terminal of the switching transistor and the pull down diode of the third stage. The gate terminal of the blocking transistor is electrically coupled to the source terminal of the switching transistor of the first stage where the first stage provides the output for the negative charge pump circuit. A voltage present at the output of the first stage is delivered to the gate terminal of the switching transistor of the third stage when a positive programming voltage is present at the output of the first stage in order to block the positive programming voltage from shorting to ground through the negative pump circuit.

Abstract: A negative charge pump circuit is disclosed. The pump circuit includes several stages, each stage including a switching transistor, a pull up diode, and a pull down diode. The pump circuit also includes a blocking transistor coupled between the gate terminal of the blocking transistor is electrically coupled to the source terminal of the switching transistor of the first stage where the first stage provides the output for the negative charge pump circuit. A voltage present at the output of the first stage is delivered to the gate terminal of the switching transistor of the third stage when a positive programming voltage is present at the output of the first stage in order to block the positive programming voltage from shorting to ground through the negative pump circuit. The blocking transistor prevents the voltage applied to the gate of the switching transistor of the third stage from flowing through the pull-down diode of the third stage.