Digital signal sampler
AssigneeT-Ram, Inc.
InventorBruce L. Bateman
Life of this patent
Estimating the term…
Abstract
A sampling circuit for testing an integrated circuit receives several signals from points of interest in the integrated circuit, digitizes them, and determines whether the digitized signal is above or below a threshold. By sampling the signal at different phases of a system clock signal, a determination can be made of when during the system clock signal the signal at a point of interest changed state. Circuits are provided for making minimal impact on the circuit being observed. Circuits are also provided for clocking the observed signal so that it can be compared to other observed signals.
Claims13
A method for testing a group of periodic signals generated by at least one circuit in a semiconductor device operating under a system clock signal, comprising:
- (a) providing a selection signal for selecting a first one of the group of periodic signals;
- (b) providing a strobe signal,
- (c) capturing a state of the first periodic signal in response to the strobe signal;
- (d) generating an output signal that is associated with the captured periodic signal;
- (e) shifting the strobe signal in time relative to the system clock signal;
- (f) repeating steps (c), (d) and (e) using the time shifted strobe signal until a termination criterion is met;
- and
- (g) providing another selection signal for selecting a second one of the group of periodic signals and repeating steps (b), (c), (d), (e) and (f) using the second periodic signal.
A signal testing system comprising:
- a tester generating a clock signal and a strobe signal that can be time shifted relative to the clock signal;
- an integrated circuit operating under the clock signal and generating at least a first and a second periodic signals, comprising:
- a plurality of pads including a first pad for accepting the clock signal, a second pad for accepting the strobe signals, and a third pad for delivering an output signal;
- a first and a second circuit for generating a first and a second state from the first and the second periodic signals, respectively;
- the first and the second circuits having substantially similar delays;
- a first and a second capturing device to capture the first and the second states, respectively, in response to the strobe signal;
- and
- an output device for providing to the third pad the output signal associated with one of the two captured states.
Dependencies are inferred from the claim text.