Classifications

• • H—ELECTRICITY
  • H03—ELECTRONIC CIRCUITRY
  • H03K—PULSE TECHNIQUE
  • H03K3/00—Circuits for generating electric pulses; Monostable, bistable or multistable circuits
  • H03K3/02—Generators characterised by the type of circuit or by the means used for producing pulses
  • H03K3/027—Generators characterised by the type of circuit or by the means used for producing pulses by the use of logic circuits, with internal or external positive feedback
  • H03K3/03—Astable circuits
  • H03K3/0307—Stabilisation of output, e.g. using crystal
• • H—ELECTRICITY
  • H03—ELECTRONIC CIRCUITRY
  • H03K—PULSE TECHNIQUE
  • H03K3/00—Circuits for generating electric pulses; Monostable, bistable or multistable circuits
  • H03K3/01—Details
  • H03K3/012—Modifications of generator to improve response time or to decrease power consumption

Definitions

• the invention relates generally to clock signal oscillators and more specifically to an arrangement for low power clock signal generation in such oscillators.
• a high frequency, e.g. 13 MHz, clock signal is needed for different operating modes such as transmit, receive, etc. Since high frequency accuracy, typically +/-10 ppm, is required in transmit and receive modes, this 13 MHz clock signal is generated by means of an accurate crystal oscillator.
• a low frequency, e.g. 3.2 kHz, clock signal with a lower frequency accuracy requirement, typically +/- 250 ppm, is needed and low power consumption is desired.
• the object of the invention is to provide an arrangement for generating a clock signal with less power in a high accuracy crystal oscillator that comprises a gain stage controlled by a current from a current source, and a trimmable load capacitance.
• the arrangement according to the invention comprises a mode control unit for disconnecting at least part of the load capacitance and activating an oscillation amplitude regulator that is connected between the input terminal of the gain stage and the current source to reduce the current to the gain stage to such a value that oscillation is maintained with a minimum amplitude.
• FIG. 1 is a simplified schematic of an oscillator circuit with an embodiment of an arrangement according to the invention.
• Fig. 1 is a simplified schematic of a 13 MHz crystal oscillator circuit that comprises a crystal 1.
• the crystal 1 is connected with one of its terminals to an input terminal of a gain stage 2 and to ground via a trimmable load capacitance 3, and with its other terminal to an output terminal of the gain stage 2 and to ground via a trimmable load capacitance 4.
• trimmable load capacitance 3 By trimming the load capacitance 3, 4, high frequency accuracy, typically +/-10 ppm, is achieved.
• the gain of the gain stage 2 is proportional to the current supplied by a variable current source 5 to the gain stage 2.
• the oscillation amplitude at the output of the gain stage 2 is a function of its gain, i.e. the higher gain, the higher oscillation amplitude.
• an oscillation amplitude regulator 6 is connected with its input terminal to the input terminal of the gain stage 2, with its output terminal to a control input terminal of the current source 5, and with a control input terminal to an output terminal of a mode control unit 7.
• the oscillation amplitude is also a function of load capacitance, i.e. the less load capacitance, the higher oscillation amplitude is achieved for a certain gain. Therefore, the output terminal of the mode control unit 7 is also connected to control input terminals of the trimmable load capacitance 3, 4 making it possible to disconnect all or at least part of the load capacitance in sleep mode.
• a frequency divider 8 is connected to the output terminal of the oscillator 2 to provide a 3.2 kHz clock signal.
• the divider 8 is running in all operating modes, including sleep mode, since the 3.2 kHz clock is needed all the time.
• the oscillator circuit can be switched between an operating mode and a sleep mode.
• the mode control unit 7 is adapted to generate a control signal to disconnect at least part of the load capacitance 3, 4. By disconnecting part of the load capacitance 3, 4, less current will be needed from the current source 5 to the gain stage 2 to achieve a certain oscillation amplitude.
• the load capacitance 3, 4 can be decreased since the accuracy requirements for the 3.2 kHz clock signal are relatively low, e.g. 250 ppm.
• the control signal from the mode control unit 7 is also applied to the oscillation amplitude regulator 6 that is activated to reduce the current from the current source 5 to the gain stage 2 to such a value that oscillation is maintained with a minimum amplitude sufficient for proper frequency division performed by the divider 8.
• the 13 MHz clock signal can be blocked in sleep mode by means of e.g. a gate.
• a gate In the embodiment in Fig. 1, this is done by an AND gate 9 that is connected with its one input terminal to the output terminal of the gain stage 2 and with its other input terminal to the output terminal of the mode control unit 7.

Landscapes

• Chemical & Material Sciences (AREA)
• Crystallography & Structural Chemistry (AREA)
• Oscillators With Electromechanical Resonators (AREA)

Priority Applications (5)

Applications Claiming Priority (2)

Related Child Applications (1)

Publications (1)

Family

ID=20288145

Family Applications (1)

Country Status (7)

Cited By (2)

Families Citing this family (7)

Citations (6)

• 2002
  • 2002-06-07 SE SE0201774A patent/SE0201774L/ not_active Application Discontinuation
• 2003
  • 2003-05-21 EP EP03757224A patent/EP1514343B1/en not_active Expired - Lifetime
  • 2003-05-21 AU AU2003232707A patent/AU2003232707A1/en not_active Abandoned
  • 2003-05-21 WO PCT/SE2003/000821 patent/WO2003105333A1/en active Application Filing
  • 2003-05-21 DE DE60329842T patent/DE60329842D1/de not_active Expired - Lifetime
  • 2003-05-21 JP JP2004512281A patent/JP2005529534A/ja active Pending
  • 2003-05-21 CN CNB038130165A patent/CN100477485C/zh not_active Expired - Fee Related

Patent Citations (6)

Non-Patent Citations (3)

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