Digital-to-analog converter with switching elements controlled by a microcontroller

• US 9,608,660 B2
• Filed: 04/03/2014
• Issued: 03/28/2017
• Est. Priority Date: 04/08/2013
• Status: Expired due to Fees

• Current Assignee: Renesas Electronics Corporation
• Original Assignee: Renesas Electronics Corporation
• Inventors: Vohora, Bushan
• Primary Examiner(s): JEAN PIERRE, PEGUY
• Application Number:
  US14/783,321
• Publication Number:
  US 20160065233A1
• Time in Patent Office: 1,090 Days
• Field of Search: 341/144, 341/143, 341/118, 341/155, 341/150
• US Class Current: 1/1
• CPC Class Codes: H03M 1/0626 by filtering
• CPC Class Codes: H03M 1/661 Improving the reconstruction of the analogue output signal beyond the resolution of the digital input signal, e.g. by interpolation, by curve-fitting, by smoothing
• CPC Class Codes: H03M 1/668 Servo-type converters
• CPC Class Codes: H03M 1/82 with intermediate conversion to time interval

Abstract

A digital-to-analog converter (DAC) is described. The DAC comprises a resistor having a resistance R and a capacitor having a capacitance C. The DAC comprises a first switching element configured, in response to a first control signal, to couple the capacitor to a first rail via a path having a resistance less than R and a second switching element configured, in response to a second control signal, to couple the capacitor to the first rail through the resistor. The DAC also comprises a third switching element configured, in response to a third control signal, to couple the capacitor to a second rail (8) via a path having a resistance less than R and a fourth switching element configured, in response to a responsive to a fourth control signal, to couple the capacitor to the second through the resistor. The capacitor can be quickly charged or discharged over a period less than RC or less than 0.7 RC. The DAC may comprise a first control element configured to switch on the second switching element before switching on the first switching element and a second control element configured to switch on the fourth switching element before switching on the third switching element.

Claims

1. Apparatus comprising:

a digital-to-analog converter comprising;

a resistor having a resistance R;

a capacitor having a capacitance C;

a first switching element which couples the capacitor to a first rail via a path having a resistance less than R in response to a first control signal;

a second switching element which couples the capacitor to the first voltage rail through the resistor in response to a second control signal;

a third switching element which couples the capacitor to a second rail via a path having a resistance less than R in response to a third control signal, and

a fourth switching element which couples the capacitor to the second rail through the resistor in response to a fourth control signal;

and a microcontroller which provides and/or causes generation of the control signals to generate an analog output signal based on a digital input signal,

wherein a control signal is applied for a duration less than RC.

2. Apparatus according to claim 1, comprising:

a first control element which switches on the second switching element before switching on the first switching element; and

a second control element which switches on the fourth switching element before switching on the third switching element.

3. Apparatus according to claim 2, wherein the first and second control elements introduce first and second propagation delays respectively.

4. Apparatus according to claim 3, wherein the first and/or second propagation delay(s) is (are) no more than 50 ns, no more than 20 ns or no more than 10 ns.

5. Apparatus according to claim 3, wherein the first and/or second propagation delay(s) is (are) at least 1 ns, at least 2 ns or at least 5 ns.

6. Apparatus according to claim 1, comprising:

a first path between a control signal input and a control terminal of the first switching element via an element which introduces a first delay; and

a second path between the control signal input and a control terminal of the second switching element without an element which introduces a delay or via an element which introduces a delay less than the first delay.

7. Apparatus according to claim 1, comprising:

a third path between another control signal input and a control terminal of the third switching element via another element which introduces a second delay; and

a fourth path between the other control signal input and a control terminal of the fourth switching element without an element which introduces a delay or via an element which introduces a delay less than the second delay.

8. Apparatus according to claim 1, wherein the first switching element couples the capacitor directly to the first rail.

9. Apparatus according to claim 1, wherein the third switching element couples the capacitor directly to the second rail.

10. Apparatus according to claim 1, comprising a single capacitor between the first and second rails.

11. Apparatus according to claim 1, wherein the first control element provides the first control signal in dependence upon the second control signal and a fifth control signal.

12. Apparatus according to claim 1, wherein the first control element comprises a logic gate.

13. Apparatus according to claim 1, wherein the second control element provides the third control signal in dependence upon the fourth control signal and a sixth control signal.

14. Apparatus according to claim 1, wherein the second control element comprises a logic gate.

15. Apparatus according to claim 1, wherein the first and third switching elements are arranged in a push-pull configuration.

16. Apparatus according to claim 1, wherein the first and third switching elements comprise first and third transistors.

17. Apparatus according to claim 16, wherein the first and third transistors comprise bipolar junction transistors.

18. Apparatus according to claim 1, wherein the second and fourth switching elements are arranged in a push-pull configuration.

19. Apparatus according to claim 1, wherein the second and fourth switching elements comprise second and fourth transistors.

20. Apparatus according to claim 19, wherein the second and fourth transistors are bipolar junction transistors.

21. A method of controlling an apparatus, the apparatus comprising a resistor having a resistance R, a capacitor having a capacitance C and at least one switching element which couples the capacitor to a voltage rail through the resistor in response to a control signal, and a microcontroller which provides and/or causes generation of the control signal, the method comprising:

applying the control signal for a duration less than RC,

when the capacitor is in a discharged state, initially charging the capacitor through the resistor for a given time period and then charging the capacitor via a path having a resistance less than R, and

when the capacitor is in charged state, initially discharging the capacitor through the resistor for a given time period and then discharging the capacitor via a path having a resistance less than R.

22. A method of controlling an apparatus, the apparatus comprising a first switching element which couples the capacitor to a first rail via a path having a resistance less than R in response to a first control signal, a second switching element which couples the capacitor to the first voltage rail through the resistor in response to a second control signal, a third switching element which couples the capacitor to a second rail via a path having a resistance less than R in response to a third control signal, and a fourth switching element which couples the capacitor to the second rail through the resistor in response to a fourth control signal, and a microcontroller which provides and/or causes generation of the control signal, wherein the method comprises:

applying the first, second, third or fourth control signal for a duration less than RC.