Multi-standard, automatic impedance controlled driver with supply regulation

Patent metadata

Field	Value
Publication number	US-9753479-B2
Application number	US-201213564150-A
Country	US
Kind code	B2
Filing date	Aug 1, 2012
Priority date	Aug 1, 2012
Publication date	Sep 5, 2017
Grant date	Sep 5, 2017

Abstract

A pre-driver circuit generates a driver bias signal based on a swing command, a driver impedance characteristic, and an input signal. A driver receives the driver bias signal and generates, in response, a driver signal having a swing and having an output impedance corresponding to the bias signal. Optionally, the driver receives power from a switchable one of multiple supply rails, according to the swing. Optionally, the driver has voltage controlled resistor elements and the driver bias signal is generated based on the swing command and a replica of the driver voltage controlled resistor elements.

First claim

What is claimed is:

1. A regulated output impedance driver, comprising:
a driver supply;
a plurality of pre-driver slices each configured to generate a driver bias signal based at least in part on a swing command, a driver impedance characteristic, and an input signal; and
a plurality of driver slices each coupled to the driver supply and each having a driver output, the plurality of drivers slices each being configured to receive the driver bias signal and generate, in response, at the driver output a driver signal having a swing and an output impedance corresponding to the driver bias signal,
the pre-driver circuit being configured to automatically adjust the driver bias signal such that the output impedance at the driver output is varied to match an impedance of a given line; and further comprising:
a programmable swing control circuit configured to generate a swing control signal;
the plurality of pre-driver slices, each pre-driver slice being configured to output a driver bias
signal based on the swing control signal; and
the plurality of driver slices connected in parallel with commonly connected outputs, each
driver slice being configured to output a driver signal based on the driver bias signal from a corresponding pre-driver slice,
the programmable swing control circuit being configured to control the plurality of pre-driver slices to output the driver bias signals to automatically control output impedances of the plurality of driver slices, and each driver slice being capable of outputting a pull-up driver signal and a pull-down driver signal; and the output impedance of each driver slice being controlled such that an aggregate output impedance of the plurality of driver slices is a desired output impedance R_Spec, the aggregate output impedance being an impedance of parallel connected outputs of the plurality of driver slices.

2. The regulated output impedance driver of claim 1 , the driver supply comprising:
a voltage regulator having an input and an output; and
a supply select switch receiving a first supply rail and a second supply rail and configured to selectively switch, based on a target swing, a coupling of the voltage regulator input between the first supply rail and the second supply rail.

3. The regulated output impedance driver of claim 1 , the pre-driver circuit comprising:
a pre-driver control circuit configured to generate a pre-driver swing control signal based at least in part on the swing command and the driver impedance characteristic; and
a pre-driver configured to generate the driver bias signal based at least in part on the input signal and the pre-driver swing control signal.

4. The regulated output impedance driver of claim 3 ,
the driver comprising a voltage-controlled resistor element associated with the driver impedance characteristic,
the pre-driver control circuit comprising a replica of the voltage-controlled resistor element, and
the pre-driver control circuit being configured to generate the driver bias signal further based on the replica of the voltage-controlled resistor element.

5. The regulated output impedance driver of claim 4 , the pre-driver control circuit comprising:
a reference resistor;
a reference resistor current source configured to set a reference current through the reference resistor that establishes a voltage on the reference resistor corresponding to the swing command;
a bias voltage detector configured to identify a reference bias voltage that when applied to the replica of the voltage-controlled resistor element establishes a voltage on a current input of the replica of the voltage-controlled resistor element corresponding to the voltage established on the reference resistor; and
a pre-driver swing control signal generator configured to generate the pre-driver swing control signal based at least in part on the reference bias voltage.

6. The regulated output impedance driver of claim 5 , the bias voltage detector comprising:
a replica reference current source controllable by the voltage established on the reference resistor, configured to pass a current through the replica of the voltage-controlled resistor element; and
a comparator that varies the reference bias voltage on the replica of the voltage-controlled resistor element to establish said voltage on the current input.

7. The regulated output impedance driver of claim 5 , the pre-driver control circuit further comprising a driver mid-point offset generator configured to generate a driver mid-point offset signal based at least in part on the reference bias voltage.

8. The regulated output impedance driver of claim 7 , the driver mid-point offset generator being configured to generate the driver mid-point offset signal at a level of one-half the reference bias voltage.

9. The regulated output impedance driver of claim 1 ,
the pre-driver circuit comprising a pre-driver control circuit configured to generate a pre-driver swing control signal based at least in part on a swing command and the driver impedance characteristic, and a pre-driver configured to generate the driver bias signal based at least in part on the input signal and the pre-driver swing control signal,
the driver comprising a circuit leg comprising a switched pull-up element switchably coupling the driver output to the driver supply and a switched pull-down element switchably coupling the driver output to a ground reference,
the switched pull-up element comprising a voltage controlled pull-up resistor element in series with a pull-up resistor, and the switched pull-down element comprising a voltage controlled pull-down resistor element in series with a pull down resistor,
the pre-driver control circuit comprising a replica of the circuit leg; having a replica of the switched pull-up element switchably coupling the driver output to the driver supply and a replica of the switched pull-down element switchably coupling the driver output to a ground reference, and
the replica of the switched pull-up element comprising a replica of the voltage controlled pull-up resistor element in series with a replica of the pull-up resistor, and the replica of the switched pull-down element comprising a replica of the voltage controlled pull-down resistor element in series with a replica of the pull down resistor.

10. The regulated output impedance driver of claim 9 , the pre-driver control circuit comprising:
a reference resistor;
a reference resistor current source configured to establish a reference current through the reference resistor that establishes a voltage on the reference resistor corresponding to the swing command;
a bias voltage detector configured to identify a reference bias voltage that when applied to the replica of the voltage controlled resistor element establishes a voltage corresponding to the voltage established on the reference resistor; and
a pre-driver swing control signal generator configured to generate a pre-driver swing control signal based at least in part on the reference bias voltage.

11. The regulated output impedance driver of claim 1 , the regulated output impedance driver being integrated in at least one semiconductor die.

12. The regulated output impedance driver of claim 1 , further comprising a device, selected from the group consisting of a set top box, music player, video player, entertainment unit, navigation device, communications device, personal digital assistant (PDA), fixed location data unit, and a computer, into which the regulated output impedance driver is integrated.

13. A method for regulating output impedance of a driver, the method comprising:
generating a driver bias signal based on a swing command, a

Assignees

• Hafizi Madjid
• Xu Jie
• Kong Xiaohua
• Dang Nam V
• Qualcomm Inc

Inventors

• Hafizi Madjid
• Xu Jie
• Kong Xiaohua
• Dang Nam V

Classifications

• H04L25/0278

  Arrangements for impedance matching · CPC title

• H04L25/028

  Arrangements specific to the transmitter end · CPC title

• H03F2200/03

  the amplifier being designed for audio applications · CPC title

• G05F3/08 Primary

  wherein the variable is DC · CPC title