Comparator with adaptive timing

• US 8,487,659 B2
• Filed: 04/22/2011
• Issued: 07/16/2013
• Est. Priority Date: 04/22/2011
• Status: Active Grant

• Current Assignee: Analog Devices, Inc.
• Original Assignee: Analog Devices, Inc.
• Inventors: Kapusta, Ronald
• Primary Examiner(s): LUU, AN T
• Application Number:
  US13/092,465
• Publication Number:
  US 20120268185A1
• Time in Patent Office: 816 Days
• Field of Search: 327/3, 327/9, 327/12, 327/33, 327/37, 327/43, 327/45, 327/51, 327/52, 327/57
• US Class Current: 327/3
• CPC Class Codes: H03K 2005/00065 by current control, e.g. by parallel current control transistors
• CPC Class Codes: H03M 1/0617 characterised by the use of methods or means not specific to a particular type of detrimental influence
• CPC Class Codes: H03M 1/0836 of phase error, e.g. jitter
• CPC Class Codes: H03M 1/46 with digital/analogue converter for supplying reference values to converter

Abstract

An adaptive delay device that provides a delay to a signal based on circuit conditions such as temperature, supply voltage values and/or fabrication processes. The adaptive delay device may respond to circuit conditions by charging a capacitive device to a threshold voltage. A comparator may incorporate the adaptive delay device to provide adaptive timing for the comparator functions thereby attaining improved noise performance and/or reduce power consumption.

Claims

1. A comparator, comprising:

a preamplifier responsive to a first control signal;

a latch responsive to a second control signal; and

a delay element, having an input for the first control signal and an output for the second control signal, the delay element having a circuit structure to adaptively increase or decrease delay propagation of the first control signal in a manner that counteracts PVT effects present in other components of the comparator.

2. The comparator of claim 1, wherein the delay element further comprises:

a capacitive element for supplying a threshold voltage to a control input of an output switch; and

an intermediate switch for selectively delivering a current to the capacitive element, wherein the capacitive element charges to a threshold voltage that actuates the output switch which changes an output signal, wherein a time required to charge the capacitive element to the threshold voltage varies in response to circuit conditions of the comparator.

3. The comparator of claim 2, wherein a current source provides the current to the capacitive element, and the current is proportional to the temperature of circuit components of the comparator.

4. The comparator of claim 3, wherein the current source comprises:

a first pair of transistors configured as a current mirror;

a second pair of transistors with commonly connected control inputs connected to a drain terminal of one transistor of the first pair of transistors; and

a single transistor with a control input connected to a terminal of a resistive element.

5. A successive approximation register analog-to-digital converter on an integrated circuit chip configured with a plurality of on-chip circuit components, comprising:

a comparator for determining whether an input signal is representative of a digital high or low signal; and

an adaptive delay device having an input for receiving a control signal and an output connected to the comparator, wherein the adaptive delay device is configured to respond inversely to the response of other circuit components forming the successive approximation register analog-to-digital converter, and output the control signal to the comparator based on the inverse response of the adaptive delay device.

6. The successive approximation register analog-to-digital converter of claim 5, wherein the adaptive delay device further comprises:

a capacitive element for supplying a threshold voltage to a control input of an output switch; and

an intermediate switch for selectively delivering a current to the capacitive element, wherein the capacitive element charges to a threshold voltage that actuates the output switch which changes an output signal, wherein the time required to charge the capacitive element to the threshold voltage is responsive to circuit conditions of the converter.

7. The successive approximation register analog-to-digital converter of claim 6, wherein the current is proportional to the temperature of circuit components of the converter, and provided by a current source.

8. The successive approximation register analog-to-digital converter of claim 7, wherein the current source comprises:

a first pair of transistors configured as a current mirror;

a second pair of transistors with commonly connected control inputs connected to a drain terminal of one transistor of the first pair of transistors; and

a single transistor with a control input connected to a terminal of a resistive element.

9. A method of controlling PVT effects in a circuit system, comprising:

responsive to a state change in an input signal, charging a capacitive element with reference to a first supply voltage; and

when the capacitive element'"'"'s output voltage reaches a voltage threshold, generating an output voltage;

wherein the method is performed in an integrated circuit, and delays between the state change of the input signal and the generated output voltage vary inversely in response to PVT effects on other components of the integrated circuit.

10. The method of claim 9, wherein the voltage threshold is set by determining when an output voltage of the capacitive element is within a voltage threshold of a second supply voltage, opposite from the first supply voltage.

11. The method of claim 9, wherein the generated output voltage is a same voltage as the input signal.