US 2008/0258795 A1 · LOW POWER OSCILLATOR

Abstract

A CMOS low frequency oscillator circuit comprising an amplifier (10) and an interface for connecting a first and a second terminal of an external crystal oscillator (14) in a feedback path of the amplifier (10). In one aspect, the oscillator circuit further comprises a regulated current source (24) supplying a regulated current to the amplifier (10) controlled by the voltage swing across the external crystal oscillator (14); and a constant current source (32) supplying a minimum constant current to the amplifier (10) independent of the voltage swing across the external crystal oscillator (14). In another aspect, the oscillator circuit further comprises an output stage (34) for converting an analog oscillator signal provided at the first and second terminals of the external crystal oscillator into a digital clock signal; wherein the output stage has a differential input (36) and a single-ended output (38) and includes a comparator (40) coupled with its differential input to the two terminals of the external crystal (14), the comparator (40) having a single-ended output; two parallel branches (42, 44) of series-connected inverters (42a, 42b, 42c, 44a, 44b, 44c), each branch having an input connected to the output of the comparator (40); a dynamic inverter (46) with complementary inputs each connected to a different output of the two parallel circuit branches (42, 44); and a plurality of series-connected output inverters (48, 50, 52).

Claims20

Dependent claims

A CMOS low frequency oscillator circuit, comprising:

an amplifier;
an interface having first and a second terminals for connecting an external crystal oscillator in a feedback path of the amplifier;
a regulated current source connected, configured and adapted for supplying a regulated current to the amplifier controlled by a voltage swing across the oscillator first and second terminals;
and
a constant current source connected, configured and adapted for supplying a minimum constant current to the amplifier independent of the voltage swing.

2 more elements

A CMOS low frequency oscillator circuit, comprising:

an amplifier;
an interface having first and a second terminals for connecting an external crystal oscillator in a feedback path of the amplifier;
a regulated current source connected, configured and adapted for supplying a regulated current to the amplifier controlled by a voltage swing across the oscillator first and second terminals;
a constant current source connected, configured and adapted for supplying a minimum constant current to the amplifier independent of the voltage swing;
and
an output stage for converting an analog oscillator signal provided at the oscillator first and second terminals into a digital clock signal;
the output stage including:
a comparator having a single-ended output and a differential input with terminals respectively coupled to the oscillator first and second terminals;
two parallel branches of series-connected inverters, each branch having an input connected to the output of the comparator and having an output;
and
a dynamic inverter with two inputs, each connected to an output of a different one of the two parallel circuit branches.

8 more elements

Dependencies are inferred from the claim text.

Low power oscillator

Life of this patent

Low power oscillator

Life of this patent

Abstract

Claims20