US 2003/0111669 A1Published application

CMOS relaxation oscillator circuit with improved speed and reduced process/temperature variations

AssigneeElantec Semiconductor, Inc.

InventorXijian Lin

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Abstract

An improved relaxation oscillator circuit is provided using conventional CMOS device shunted with a current source (101 and 103) at each load of two cross-coupled gain stages. The improved oscillator uses a clamp voltage reference (134), to control the voltage swing across the charging/discharging capacitor (118). The improvements provide improved speed to power ratio, increased frequency tuning range, and less process and temperature variation effects. A transistor (130) and current source (138) replicate output transistors (110, 114) and current sources (101, 103). An amplifier (132) receives a clamp voltage reference (134) and current from the transistor (130) and current source (138) and functions to provide necessary drive currents to the gates of transistors (110, 114) which drive the outputs (VOR, VOL)

Claims21

Dependent claims

A relaxation oscillator circuit, comprising:

a first current source (101) coupling a first voltage source (199) to a first node (VOR);
a first transistor (110) having a drain connected to the first voltage source (199), a gate forming a second node, and a source connected to the first node (VOR);
a second current source (103) coupling the first voltage source (199) to a third node (VOL);
a second transistor (114) having a drain connected to the first voltage source (199), a gate connected to the second node, and a source connected to the third node (VOL);
a third transistor (112) having a drain connected to the first node (VOR), a gate connected to the third node (VOL), and a source forming a fourth node (VSR);
a fourth transistor (116) having a drain connected to the third node (VOL), a gate connected to the first node (VOR), and a source forming a fifth node (VSL);
a first current sink (105) coupling a second voltage source (198) to the fourth node (VSR);
a second current sink (107) coupling the second voltage source (198) to the fifth node (VSL);
a capacitor (118) coupling the fourth node (VSR) to the fifth node (VSL);
a fifth transistor (130) having a drain connected to the first voltage source (199), a gate connected to the second node, and a source forming a sixth node;
a third current source (138) coupling the first voltage source (199) to the sixth node;
a third current sink (136) coupling the second voltage source (198) to the sixth node;
an amplifier (132) having an output connected to the second node, an inverting terminal connected to the sixth node, and a non-inverting terminal;
and
a third voltage source (134) coupling the non-inverting terminal of the amplifier (132) to the first voltage source (199).

12 more elements

A relaxation oscillator circuit, comprising:

a first current source (101) coupling a first voltage source (199) to a first node (VOR);
a first transistor (110) having a drain-source path coupling the first voltage source (199) to the first node (VOR), and having a gate forming a second node;
a second current source (103) coupling the first voltage source (199) to a third node (VOL);
a second transistor (114) having a drain-source path connecting the first voltage source (199) to the third node (VOL), and having a gate connected to the second node;
a third transistor (112) having a drain-source path connecting the first node (VOR) to a fourth node (VSR), and having a gate connected to the third node (VOL);
a fourth transistor (116) having a drain-source path coupling the third node (VOL) to a fifth node (VSL), and having a gate connected to the first node (VOR);
a first current sink (105) coupling a second voltage source (198) to the fourth node (VSR);
a second current sink (107) coupling the second voltage source (198) to the fifth node (VSL);
a capacitor (118) coupling the fourth node (VSR) to the fifth node (VSL);
a fifth transistor (130) having a drain-source path coupling the first voltage source (199) to a sixth node, and having a gate connected to the second node;
a third current source (138) coupling the first voltage source (199) to the sixth node;
a third current sink (136) coupling the second voltage source (198) to the sixth node;
an amplifier (132) having an output connected to the second node, an inverting terminal connected to the sixth node, and a non-inverting terminal;
and
a third voltage source (134) coupling the non-inverting terminal of the amplifier (132) to the first voltage source (199).

12 more elements

A relaxation oscillator circuit, comprising:

a first current source (101) coupling a first voltage source (199) to a first node (VOR);
a first transistor (110) having a collector-emitter path connecting to the first voltage source (199) to the first node (VOR), and having a base forming a second node;
a second current source (103) coupling the first voltage source (199) to a third node (VOL);
a second transistor (114) having a collector-emitter path connecting the first voltage source (199) to the third node (VOL), and having a base connected to the second node;
a third transistor (112) having a collector-emitter path connecting the first node (VOR) to a fourth node (VSR), and having a base connected to the third node (VOL);
a fourth transistor (116) having a collector-emitter path connected to the third node (VOL) to a fifth node (VSL), and having a base connected to the first node (VOR);
a first current sink (105) coupling a second voltage source (198) to the fourth node (VSR);
a second current sink (107) coupling the second voltage source (198) to the fifth node (VSL);
a capacitor (118) coupling the fourth node (VSR) to the fifth node (VSL);
a fifth transistor (130) having a collector-emitter path connecting the first voltage source (199) to a sixth node, and having a base connected to the second node;
a third current source (130) coupling the first voltage source (199) to the sixth node;
a third current sink (136) coupling the second voltage source (198) to the sixth node;
an amplifier (132) having an output connected to the second node, an inverting terminal connected to the sixth node, and a non-inverting terminal;
and
a third voltage source (134) coupling the non-inverting terminal of the amplifier (132) to the first voltage source (199).

12 more elements

A relaxation oscillator circuit, comprising:

a first current source (101) coupling a first voltage source (199) to a first node (VOR);
a first transistor (110) including a first terminal coupled with a second terminal forming a path coupling the first voltage source (199) to the first node (VOR), and a control terminal connected between the first terminal and the second terminal;
a second current source (103) coupling the first voltage source (199) to a third node (VOL);
a second transistor (114) including a first terminal coupled with a second terminal forming a path coupling the first voltage source (199) to the third node (VOL), and a control terminal connected between the first terminal and the second terminal;
a third transistor (112) including a first terminal coupled with a second terminal forming a path coupling the first node (VOR) to a fourth node (VSR), and a control terminal connected between the first node and the second node, the control terminal connected to the third node (VOL);
a fourth transistor (116) including a first terminal coupled with a second terminal forming a path coupling the third node (VOL) to a fifth node (VSL), and a control terminal connected between the first node and the second node, the control terminal connected to the first node (VOR);
a first current sink (105) coupling a second voltage source (198) to the fourth node (VSR);
a second current sink (107) coupling the second voltage source (198) to the fifth node (VSL);
a capacitor (118) coupling the fourth node (VSR) to the fifth node (VSL);
a fifth transistor (130) including a first terminal coupled with a second terminal forming a path coupling the first voltage source (199) to a sixth node, and a control terminal connected between the first node and the second node, the control terminal connected to the second node;
a third current source (138) coupling the first voltage source (199) to the sixth node;
a third current sink (136) coupling the second voltage source (198) to the sixth node;
an amplifier (132) having an output connected to the second node, an inverting terminal connected to the sixth node, and a non-inverting terminal;
and
a third voltage source (134) coupling the non-inverting terminal of the amplifier (132) to the first voltage source (199).

12 more elements

Dependencies are inferred from the claim text.