Temperature compensated voltage pump
View Patent ↗The present invention relates to an integrated circuit voltage pump with temperature compensation circuitry providing improved DC output voltage accuracy over an operational temperature range. The compensation circuitry is operative to eliminate or reduce temperature induced changes of voltage drops across semiconductor diodes of the integrated circuit voltage pump.
1. An integrated circuit voltage pump comprising:
an input terminal adapted to receive a DC input voltage;
an output terminal supplying a DC output voltage derived from the DC input voltage;
a pump stage disposed in-between the input terminal and the output terminal and comprising first and second semiconductor diodes electrically connected to first and second pump capacitors, respectively, each of first and second semiconductor diodes having a diode voltage drop with a predetermined temperature coefficient in conducting mode;
a compensation circuit adapted to generate first and second non-overlapping voltages pulses of respective amplitudes based on first and second non-overlapping clock signals and apply the first and second voltage pulses to the first and second pump capacitors, respectively,
the compensation circuit being adapted to adjust an amplitude of at least one of the first and second non-overlapping voltage pulses to compensate for temperature induced changes in at least one of the diode voltage drops,
the compensation circuit configured to derive the respective amplitudes of first and second non-overlapping voltage pulses from a temperature sensitive DC voltage source having a temperature coefficient substantially identical to the temperature coefficient of the first or the second semiconductor diode;
wherein the temperature sensitive DC voltage source comprises a forward biased diode of the same type as at least one of the first and second semiconductor diodes which is connected in-between a terminal of the temperature sensitive voltage source and a substantially temperature independent DC voltage source; and
wherein the compensation circuit is supplied with power from the terminal of the temperature sensitive voltage source.
2. An integrated circuit voltage pump according to claim 1 , wherein the compensation circuit is adapted to adjust the respective amplitudes of the first and second non-overlapping voltage pulses to compensate for respective temperature induced changes of the first and second diode voltage drops.
3. An integrated circuit voltage pump according to claim 1 , comprising plurality of cascaded pump stages disposed in-between the input terminal and the output terminal.
4. An integrated circuit voltage pump according to claim 1 , wherein each semiconductor diode comprises a diode selected from a group including a poly-diode, a diffusion diode in a N-well, a diode-connected MOS transistor, and a diode-connected bipolar transistor.
5. An integrated circuit voltage pump according to claim 1 , wherein all semiconductor diodes of the pump stage, or all semiconductor diodes of the plurality of cascaded pump stages, are of same type.
6. An integrated circuit voltage pump according to claim 1 , wherein the compensation circuit comprises a clock pump circuit comprising:
a first stage coupled to the first and second non-overlapping clock signals and supplied with power from the temperature independent DC voltage source; and
a second stage operatively connected to signal outputs of the first stage and supplied with power from the temperature sensitive DC voltage to generate the first and second non-overlapping voltages pulses.
7. An integrated circuit voltage pump according to claim 1 , wherein the compensation circuit comprises:
a current sensor adapted to detect a level of current through the first or the second semiconductor diode; and
an adaptive control loop adapted to adjust a level of current through the forward biased semiconductor diode of the temperature sensitive DC voltage source to match the detected level of current through the first or the second semiconductor diode.
8. An integrated circuit voltage pump according to claim 1 , wherein the first and second pump capacitors comprise respective metal capacitors, poly-poly capacitors or MOS capacitors.
9. A condenser microphone circuit comprising:
a microphone transducer element comprising a displaceable diaphragm and an adjacently positioned perforated back plate; and
an integrated circuit voltage pump operatively connected to the microphone transducer element and configured to apply a DC bias voltage between the displaceable diaphragm the perforated back plate, wherein the integrated circuit voltage pump includes:
an input terminal adapted to receive a DC input voltage;
an output terminal supplying a DC output voltage derived from the DC input voltage;
a pump stage disposed in-between the input terminal and the output terminal and comprising first and second semiconductor diodes electrically connected to first and second pump capacitors, respectively, each of first and second semiconductor diodes having a diode voltage drop with a predetermined temperature coefficient in conducting mode;
a compensation circuit adapted to generate first and second non-overlapping voltages pulses of respective amplitudes based on first and second non-overlapping clock signals and apply the first and second voltage pulses to the first and second pump capacitors, respectively,
the compensation circuit being adapted to adjust an amplitude of at least one of the first and second non-overlapping voltage pulses to compensate for temperature induced changes in at least one of the diode voltage drops,
the compensation circuit configured to derive the respective amplitudes of first and second non-overlapping voltage pulses from a temperature sensitive DC voltage source having a temperature coefficient substantially identical to the temperature coefficient of the first or the second semiconductor diode;
wherein the temperature sensitive DC voltage source comprises a forward biased diode of the same type as at least one of the first and second semiconductor diodes which is connected in-between a terminal of the temperature sensitive voltage source and a substantially temperature independent DC voltage source; and
wherein the compensation circuit is supplied with power from the terminal of the temperature sensitive voltage source.
10. A condenser microphone circuit according to claim 9 , wherein the compensation circuit is adapted to adjust the respective amplitudes of the first and second non-overlapping voltage pulses to compensate for respective temperature induced changes of the first and second diode voltage drops.
11. A condenser microphone circuit according to claim 9 , further comprising plurality of cascaded pump stages disposed in-between the input terminal and the output terminal.
12. A condenser microphone circuit according to claim 9 , wherein each semiconductor diode comprises a diode selected from a group including a poly-diode, a diffusion diode in an N-well, a diode-connected MOS transistor, and a diode-connected bipolar transistor.
13. A condenser microphone circuit according to claim 9 , wherein all semiconductor diodes of the pump stage, or all semiconductor diodes of the plurality of cascaded pump stages, are of same type.
14. A condenser microphone circuit according to claim 9 , wherein the compensation circuit comprises a clock pump circuit comprising:
a first stage coupled to the first and second non-overlapping clock signals and supplied with power from the temperature independent DC voltage source; and
a second stage operatively connected to signal outputs of the first stage and supplied with power from the temperature sensitive DC voltage to generate the first and second non-overlapping voltages pulses.
15. A condenser microphone circuit according to claim 9 , wherein the compensation circuit comprises:
a current sensor adapted to detect a level of current through the first or the second semiconductor diode; and
an adaptive control loop adapted to adjust a level of current through the forward biased semiconductor diode of the temperature sensitive DC voltage source to match the detected level of current through the first or the second semiconductor diode.
16. A condenser microphone circuit according to claim 9 , wherein the first and second pump capacitors comprise respective metal capacitors, poly-poly capacitors or MOS capacitors.
17. A voltage pump circuit, comprising:
an input terminal to receive a DC input voltage;
an output terminal to supply a DC output voltage derived from the DC input voltage;
a pump stage connected between the input and output terminals, the pump stage including first and second diodes connected to first and second pump capacitors, each of the first and second diodes having a forward-biased diode voltage drop with a temperature coefficient; and
a compensation circuit to generate first and second non-overlapping voltage pulses as a function of first and second non-overlapping clock signals, apply the first and second voltage pulses to the first and second pump capacitors, and adjust an amplitude of at least one of the first or second non-overlapping voltage pulses as a function of a temperature sensitive DC voltage to compensate for temperature induced changes in the diode voltage drop of at least one of the first or second diodes,
wherein the compensation circuit includes a temperature sensitive DC voltage source including a third diode connected to a substantially temperature independent DC voltage source, the third diode having a forward-biased diode voltage drop with a temperature coefficient substantially the same as the temperature coefficient of the forward-biased diode voltage drop of the first or the second diodes.