US 12,224,710 B2
Low power crystal oscillator
Anand Kumar, Noida (IN); and Nitin Jain, Greater Noida (IN)
Assigned to STMicroelectronics International N.V., Geneva (CH)
Filed by STMicroelectronics International N.V., Geneva (CH)
Filed on Sep. 7, 2023, as Appl. No. 18/463,212.
Application 18/463,212 is a division of application No. 17/931,863, filed on Sep. 13, 2022, granted, now 11,901,865.
Claims priority of provisional application 63/246,026, filed on Sep. 20, 2021.
Prior Publication US 2023/0421101 A1, Dec. 28, 2023
Int. Cl. H03B 5/06 (2006.01); H03B 5/36 (2006.01)
CPC H03B 5/364 (2013.01) [H03B 5/06 (2013.01); H03B 5/366 (2013.01); H03B 2200/0082 (2013.01); H03B 2200/0094 (2013.01)] 18 Claims
OG exemplary drawing
 
1. A method for operating a low power crystal oscillator circuit, comprising:
sending a startup signal of a first polarity to a startup terminal of a crystal oscillator circuit having an output terminal and a first current supply;
driving the crystal oscillator circuit with current of a first amperage through a first current mirror having first and second current mirror transistors, the first current mirror being coupled between a high power supply and a low power supply, the crystal oscillator circuit configured to output a first voltage value at the output terminal in response to the first amperage, the startup terminal being coupled to the output terminal and to a terminal of a first startup transistor, the crystal oscillator circuit including a second current supply coupled to the low power supply and a third current mirror transistor;
maintaining the startup signal of the first polarity at the startup terminal for a first period time;
reversing the first polarity of the startup signal on the startup terminal to cause the first current mirror to turn off and cease to draw current;
driving the crystal oscillator circuit with current of a second amperage through the first current mirror; and
drawing current of the second amperage value from the first current supply which is J times less than the first amperage and the crystal oscillator circuit outputs voltage of a second voltage value which is K times less than the first voltage value at the output terminal.