Digital pulse width modulation controller with preset filter coefficients

1. A voltage regulator comprising:

at least one power switch adapted to convey power between respective input and output terminals of said voltage regulator; and

a digital controller adapted to control operation of said at least one power switch responsive to an output measurement of said voltage regulator, said digital controller comprising:

an analog-to-digital converter providing a digital error signal representing a difference between said output measurement and a reference value;

a digital filter having a transfer function defined by plural filter coefficients;

a digital pulse width modulator providing a control signal to said at least one power switch, said control signal having a pulse width corresponding to said digital control output; and

a memory containing a plurality of pre-defined coefficient sets, said digital filter being adapted to load a selected one of said pre-defined coefficient sets into said plural filter coefficients.

2. The voltage regulator of claim 1 , wherein said digital controller further comprises a multiplexer operatively coupled to said memory and to said digital filter and adapted to select one of said pre-defined coefficient sets in response to a control signal.

3. The voltage regulator of claim 2 , wherein said digital controller further comprises a selector adapted to provide said control signal to said multiplexer in response to an address signal.

4. The voltage regulator of claim 3 , wherein said address signal is received from an external host.

5. The voltage regulator of claim 3 , wherein said address signal is defined by at least one external resistor.

6. The voltage regulator of claim 1 , wherein said digital filter provides the following transfer function H(z):

H

⁡

(

z

)

=

PWM

⁡

(

z

)

VEd

⁡

(

z

)

=

C

0

+

C

1

·

z

-

1

+

C

2

·

z

-

2

+

C

3

·

z

-

3

1

-

B

1

·

z

-

1

-

B

2

·

z

-

2

-

B

3

·

z

-

3

wherein PWM(z) is the digital control output, VEd(z) is the error signal, C 0. . . C 3 are input side coefficients, and B 1 . . . B 3 are output side coefficients.

7. A method of controlling a voltage regulator comprising at least one power switch adapted to convey power between input and output terminals of said voltage regulator, said method comprising:

receiving an output measurement of said voltage regulator;

sampling said output measurement to provide a digital error signal representing a difference between said output measurement and a reference value;

filtering said digital error signal to provide a digital control output based on a transfer function defined by plural filter coefficients;

providing a control signal to said at least one power switch, said control signal having a pulse width corresponding to said digital control output;

storing a plurality of pre-defined coefficient sets; and

selectively loading a selected one of said pre-defined coefficient sets into said plural filter coefficients.

8. The method of claim 7 , wherein said selectively loading step further comprising selecting said one of said pre-defined coefficient sets in response to an externally provided address signal.

9. The method of claim 7 , wherein said selectively loading step further comprising selecting said one of said pre-defined coefficient sets in response to at least one externally coupled resistor.

10. The method of claim 7 , wherein said filtering step further comprising filtering said digital error signal using the following transfer function H(z):

H

⁡

(

z

)

=

PWM

⁡

(

z

)

VEd

⁡

(

z

)

=

C

0

+

C

1

·

z

-

1

+

C

2

·

z

-

2

+

C

3

·

z

-

3

1

-

B

1

·

z

-

1

-

B

2

·

z

-

2

-

B

3

·

z

-

3

wherein PWM(z) is the digital control output, VEd(z) is the error signal, C 0 . . . C 3 are input side coefficients, and B 1 . . . B 3 are output side coefficients.

11. A voltage regulator comprising:

at least one power switch adapted to convey power between respective input and output terminals of said voltage regulator; and

a digital controller adapted to control operation of said at least one power switch responsive to an output measurement of said voltage regulator, said digital controller comprising:

an analog-to-digital converter providing a digital error signal representing a difference between said output measurement and a reference value;

a digital filter having a transfer function defined by plural filter coefficients and means for selecting said plural filter coefficients from among a plurality of pre-defined coefficient sets; and

a digital pulse width modulator providing a control signal to said at least one power switch, said control signal having a pulse width corresponding to said digital control output.

12. The voltage regulator of claim 11 , wherein said selecting means further comprises a memory containing said plurality of pre-defined coefficient sets and a multiplexer operatively coupled to said memory and to said digital filter and adapted to select one of said pre-defined coefficient sets in response to a control signal.

13. The voltage regulator of claim 12 , wherein said digital controller further comprises a selector adapted to provide said control signal to said multiplexer in response to an address signal.

14. The voltage regulator of claim 13 , wherein said address signal is received from an external host.

15. The voltage regulator of claim 13 , wherein said address signal is defined by at least one external resistor.

16. The voltage regulator of claim 11 , wherein said digital filter provides the following transfer function H(z):

H

⁡

(

z

)

=

PWM

⁡

(

z

)

VEd

⁡

(

z

)

=

C

0

+

C

1

·

z

-

1

+

C

2

·

z

-

2

+

C

3

·

z

-

3

1

-

B

1

·

z

-

1

-

B

2

·

z

-

2

-

B

3

·

z

-

3

wherein PWM(z) is the digital control output, VEd(z) is the error signal, C 0 . . . C 3 are input side coefficients, and B 1 . . . B 3 are output side coefficients.