Patent ID: 8823424

Claim:
A circuit for improving noise immunity of a single-end level shifter in a floating gate driver having the single-end level shifter to translate a set signal and a reset signal to a common output terminal of the single-end level shifter to provide an output voltage to control a bistable circuit in reference to a voltage of an ultra-high-voltage floating well to generate a switch signal, the circuit comprising: a well transient detector connected to the common output terminal, a power input terminal of the floating gate driver, and the ultra-high-voltage floating well, detecting the output voltage to assert a well transient detect signal; and a masking circuit connected to the common output terminal, the power input terminal, and the well transient detector, masking noise in the output voltage under control of the well transient detect signal, to apply a translated set signal and a translated reset signal to the bistable circuit for turning on and turning off the switch signal, respectively; wherein the well transient detector comprises: a Zener diode and a first current source connected in series between the power input terminal and the ultra-high-voltage floating well; a second current source and a transistor connected in series between the power input terminal and the common output terminal, the transistor having a control terminal connected to the Zener diode; and a buffer having a signal input terminal connected to an output terminal of the transistor, and two bias input terminals connected to the power input terminal and the ultra-high-voltage floating well, respectively, determining the well transient detect signal according to a voltage at the output terminal of the transistor.