Time interpolator circuit
View Patent ↗A time interpolator circuit increases the accuracy of digital counting circuits.
1. A time interpolator circuit comprising:
a current source connected to a first circuit node;
a diode connected between the first circuit node and a second circuit node;
a capacitor connected between the second circuit node and ground; and,
a logic circuit including a first switch capable of connecting the first circuit node to ground and a second switch capable of connecting the second circuit node to ground.
2. The time interpolator circuit of claim 1 further comprising:
an analog-to-digital converter connected to the second circuit node.
3. The time interpolator circuit of claim 1 further comprising:
an analog-to-digital converter for measuring voltage between the second circuit node and ground.
4. The time interpolator circuit of claim 1 further comprising:
a buffer amplifier having an input connected to the second circuit node; and,
an analog-to-digital converter connected to an output of the buffer amplifier.
5. The time interpolator circuit of claim 4 , the buffer amplifier comprising an operational amplifier and a feedback resistor network.
6. The time interpolator circuit of claim 4 , the buffer amplifier input having impedance high enough to prevent discharging the capacitor through the amplifier.
7. The time interpolator circuit of claim 4 , the analog-to-digital converter measuring a voltage between the second circuit node and ground as scaled by the amplifier.
8. The time interpolator circuit of claim 1 , the first and second switches being field effect transistors.
9. The time interpolator circuit of claim 1 , the diode preventing current flow from the second circuit node to the first circuit node.
10. A frequency counter comprising:
count synchronization logic having signal, reference clock, and start/stop control inputs;
an event counter and a time counter both connected to the count synchronization logic;
a microprocessor that receives digital input from the counters and sends a start/stop control signal to the count synchronization logic; and,
an interpolator according to claim 3 , the interpolator's first and second switches connected to the count synchronization logic and digital output from the interpolator's analog-to-digital converter connected to the microprocessor.
11. A time interval counter comprising:
start synchronization logic and stop synchronization logic;
a time counter connected to the start synchronization logic and to the stop synchronization logic;
a first interpolator according to claim 3 , the first interpolator connected to the start synchronization logic; and,
a second interpolator according to claim 3 , the second interpolator connected to the stop synchronization logic.