Freescale Semiconductor,inc.

Nxp USA, Inc.

Yi Zhao

Wenzhong Zhang

Shayan Zhang

Chris C Dao

Jehoda Refaeli

Dongling Zhang

A buffer provides a signal at an output node as a function of an input signal. First and second buffer stages have respective current conduction paths for asserting the output signal. An enabling element selectively enables the second buffer stage in response to assertion of an enabling signal in a state where the first and second buffer stages are both simultaneously enabled. The first buffer stage has hysteresis feedback paths from the output node for providing hysteresis in the buffer response. The hysteresis is smaller when the first and second buffer stages are both enabled than when only the first buffer stage is enabled. The response of the second buffer stage to the input signal, when enabled, is faster than the first buffer stage.

Input buffer with selectable hysteresis and speed

An amplifier applies a self-adapting voltage to an output terminal. A bias circuit provides a greater bias current in a first external connection condition, in the absence of a pull-up resistance connected to the output terminal, than when such a pull-up resistance is present. The amplifier applies a different voltage to the output terminal in the absence of a pull-up resistance than when such a pull-up resistance is present. The circuit can be used in a portable device for receiving charging current from a battery charger through a connector having a D+ pin for connection to the battery charger and connected to the amplifier output terminal for battery charger detection. The portable device can meet the USB battery charger specification rev. 1.2.

Self-adapting voltage amplifier and battery charger detection

A comparator used in a clock signal generation circuit compares two input signals and generates an output signal. The comparator has first and second input transistors coupled to the input signals. First and second hysteresis transistors are coupled between the input transistors and an output stage of the comparator, and apply hysteresis to a comparison of the input signals. First and second hysteresis control transistors are coupled between the input transistors and the hysteresis transistors to isolate the hysteresis transistors from the input transistors under control of a hysteresis enable signal. The comparator is operable in a first mode or a second mode based on a hysteresis enable signal. In the first mode the comparator applies hysteresis to the comparison of the input signals and in the second mode, compares the input signals without hysteresis.

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Tianjin, China

Yi Zhao