Patent ID: 7187244

Claim:
An adjustable oscillator circuit for producing a pulsed output, comprising: a timing capacitor; an adjustable current source coupled to the capacitor for charging the capacitor at an adjustable rate; a threshold circuit comprising a comparator for changing a charging or discharging state of the capacitor based on a charge value of the capacitor; the threshold circuit including a first threshold value circuit providing a first threshold value to the comparator for comparison with the charge value of the capacitor when the capacitor is in a charging state and a second threshold value circuit providing a second threshold value to the comparator for comparison with the charge value of the capacitor when the capacitor is in a discharging state, further comprising a first gating switch coupled between a comparator input and the first threshold value circuit and a second gating switch coupled between the comparator input and the second threshold value circuit, said first and second gating switches being responsive to an output of the comparator to determine which of the first and second threshold values is provided to the comparator input; a first switch in the adjustable current source operable to vary the current supplied to the capacitor for charging the capacitor at the adjustable rate; a digital to analog converter coupled to a control input of the first switch and operable to receive input digital data and to provide an analog control signal to the control input of the first switch to vary the current supplied to the capacitor based on the input digital data thereby to charge the capacitor at the adjustable rate determined by the input digital data; further comprising a second switch coupled to said capacitor for discharging said capacitor and having a control input coupled to the comparator output, said first gating switch providing said first threshold value to the comparator and allowing said capacitor to be charged until the charge value of said capacitor substantially equals said first threshold value, said second gating switch providing said second threshold value to the comparator while said second switch discharges said capacitor and allowing said capacitor to be discharged until said capacitor charge value is substantially equal to said second threshold value.