LEVEL SHIFTER

• US 20180109260A1
• Filed: 10/02/2017
• Published: 04/19/2018
• Est. Priority Date: 10/17/2016
• Status: Active Grant

• Current Assignee: Kabushiki Kaisha Tokai RIKA Denki Seisakusho
• Original Assignee: Kabushiki Kaisha Tokai RIKA Denki Seisakusho
• Inventors: MATSUBARA, Junichi
• Granted Patent: US 10,312,913 B2
• Time in Patent Office: Days
• CPC Class Codes: H03K 19/00307 in bipolar transistor circuits
• CPC Class Codes: H03K 19/00315 in field-effect transistor circuits
• CPC Class Codes: H03K 19/017518 using a combination of bipolar and field effect transistors [BIFET]
• CPC Class Codes: H03K 19/01831 with at least one differential stage
• CPC Class Codes: H03K 19/0813 Threshold logic
• CPC Class Codes: H03K 19/0944 using MOSFET or insulated gate field-effect transistors, i.e. IGFETH03K19/096 takes precedence
• CPC Class Codes: H03K 3/02337 Bistables with hysteresis, e.g. Schmitt trigger non-regenerative amplitude discriminators G01R19/165
• CPC Class Codes: H03K 5/082 with an adaptive threshold

Abstract

The present disclosure provides a level shifter including: a level shifter section that is driven by a first power source voltage, and that, in accordance with switching of an input signal of a voltage lower than the first power source voltage, switches an output signal that has been level-shifted, from the first power source voltage to a voltage lower than the first power source voltage; and a threshold voltage changing circuit that, in accordance with a switching direction of the input signal, changes a threshold voltage of the input signal for switching the output signal.

Claims

1. A level shifter comprising:

a level shifter section that is driven by a first power source voltage, and that, in accordance with switching of an input signal of a voltage lower than the first power source voltage, switches an output signal that has been level-shifted, from the first power source voltage to a voltage lower than the first power source voltage; and

a threshold voltage changing circuit that, in accordance with a switching direction of the input signal, changes a threshold voltage of the input signal for switching the output signal.

2. The level shifter of claim 1, wherein the threshold voltage changing circuit is a hysteresis circuit exhibiting hysteresis characteristics with respect to changes in a voltage of the output signal in response to changes in the voltage of the input signal.

3. The level shifter of claim 1, wherein the level shifter section comprises:

a differential amplifier circuit including;

a first transistor having a first main electrode connected to the first power source voltage, a second main electrode connected to a second power source voltage of a voltage lower than the first power source voltage, and a first control electrode connected via a resistor to an input terminal to which the input signal is input,

a second transistor having a third main electrode connected to the first power source voltage and a fourth main electrode connected to a second control electrode of the second transistor and to an output terminal where the output signal is output, and

a third transistor having a first electrical conductivity type and having a fifth main electrode connected to the fourth main electrode and the output terminal and a sixth main electrode connected to the second power source voltage; and

a current mirror circuit including;

the third transistor, and

a fourth transistor having the first electrical conductivity type and having a seventh main electrode connected to the first power source voltage, an eighth main electrode connected to the second power source voltage, and a fourth control electrode connected to a third control electrode of the third transistor.

4. The level shifter of claim 3, wherein the threshold voltage changing circuit includes:

a constant current source having an input connected to the first power source voltage;

a fifth transistor having the first electrical conductivity type and having a ninth main electrode connected to an output of the constant current source, a tenth main electrode connected to the second power source voltage, and a fifth control electrode connected to a node between the output terminal, and the fourth main electrode and the fifth main electrode; and

a sixth transistor having a second electrical conductivity type opposite to that of the first electrical conductivity type and having an eleventh main electrode connected to the fourth main electrode, a twelfth main electrode connected to the fifth main electrode and the output terminal, and a sixth control electrode connected to a node between the output of the constant current source and the ninth main electrode.

5. The level shifter of claim 4, wherein:

the constant current source and the sixth transistor are configured by an offset transistor, and

the fifth transistor is configured by a vertical diffused transistor.

6. The level shifter of claim 1, further comprising a clamp section that limits the amplitude of the output signal.