CR oscillation circuit

Patent metadata

Field	Value
Publication number	US-9716501-B2
Application number	US-201615059977-A
Country	US
Kind code	B2
Filing date	Mar 3, 2016
Priority date	Apr 10, 2015
Publication date	Jul 25, 2017
Grant date	Jul 25, 2017

Abstract

A CR oscillation circuit includes inverters forming a loop for circulation of a signal, CR time constant circuits inserted into the loop for delaying the signal, each circuit having a capacitor, a plurality of resistance elements, and a transmission gate that selects an arbitrary resistance element of the plurality of resistance elements as a charge and discharge path of the capacitor, and a gate voltage generation circuit as means for outputting a gate voltage for controlling ON/OFF of each transmission gate that outputs a constant voltage in conjunction of a threshold voltage of a field-effect transistor as a gate voltage for turning ON the transmission gate.

First claim

What is claimed is:

1. A CR oscillation circuit comprising:
at least one switching gate forming a loop for circulation of a signal;
a CR time constant circuit inserted into the loop for delaying the signal, the circuit having a capacitor, a plurality of resistance elements, and a selection part that selects an arbitrary resistance element of the plurality of resistance elements as a charge and discharge path of the capacitor; and
a control section that controls ON/OFF of the selection part and controls the selection part so that temperature characteristics of a resistance value of the selection part may be constant when the selection part is turned ON,
the selection part including a transmission gate, and
the control section having a gate voltage generation unit that outputs a gate voltage for controlling ON/OFF of the transmission gate and outputs a constant voltage in conjunction with a threshold voltage of a field-effect transistor as a gate voltage for turning ON the transmission gate.

2. The CR oscillation circuit according to claim 1 , wherein
the transmission gate in the CR time constant circuit is provided on a side of an output node and the resistance element is provided on a side of the capacitor of the switching gate.

3. The CR oscillation circuit according to claim 1 , wherein
the transmission gate includes a P-channel field-effect transistor and an N-channel field-effect transistor, and the constant voltage output by the gate voltage generation unit is supplied to a substrate of the P-channel field-effect transistor or a substrate of the N-channel field-effect transistor.

4. The CR oscillation circuit according to claim 1 , wherein
the switching gate includes a P-channel field-effect transistor and an N-channel field-effect transistor, and the constant voltage output by the gate voltage generation unit is supplied to a source of the P-channel field-effect transistor or a source of the N-channel field-effect transistor of the switching gate.

5. The CR oscillation circuit according to claim 1 , wherein
the switching gate includes a P-channel field-effect transistor and an N-channel field-effect transistor, and the constant voltage output by the gate voltage generation unit is supplied to a source and a substrate of the P-channel field-effect transistor of the switching gate or a source and a substrate of the N-channel field-effect transistor of the switching gate.

6. The CR oscillation circuit according to claim 1 , wherein
the control section further includes a resistance control circuit that outputs a selection signal for designating ON/OFF of the transmission gate, and
the gate voltage generation unit includes a constant voltage generation circuit that outputs the constant voltage, and a level shifter that is supplied with the constant voltage, shifts a level of the selection signal, and outputs the gate voltage.

7. The CR oscillation circuit according to claim 6 , wherein
the level shifter includes an inverter.

8. The CR oscillation circuit according to claim 7 , wherein
the inverter includes a P-channel field-effect transistor and an N-channel field-effect transistor, and the constant voltage output by the constant voltage generation circuit is supplied to a source and a substrate of the P-channel field-effect transistor of the inverter or a source and a substrate of the N-channel field-effect transistor of the switching gate.

9. The CR oscillation circuit according to claim 1 , wherein
the gate voltage generation unit includes a constant voltage generation circuit that has a differential transistor pair of two field-effect transistors with different threshold voltages and outputs an offset voltage due to a difference between the threshold voltages as the constant voltage.

Assignees

• Seiko Epson Corp

Inventors

• Shirao Akira

Classifications

• H03K3/011 Primary

  Modifications of generator to compensate for variations in physical values, e.g. voltage, temperature {(to maintain energy constant H03K3/015)} · CPC title

• H03B5/10

  active element in amplifier being vacuum tube (H03B5/14 takes precedence) · CPC title

• H03K3/0315

  Ring oscillators · CPC title

• H03B5/04

  Modifications of generator to compensate for variations in physical values, e.g. power supply, load, temperature · CPC title

• H03L7/00

  Automatic control of frequency or phase; Synchronisation · CPC title