PLL Correction Circuit Testing via Phase Difference Output
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Solution Overview
Problem
Testing semiconductor devices with PLL circuits before product shipment is challenging due to the difficulty in accurately measuring correction currents and the potential for property deterioration from parasitic capacitance or leakage paths caused by external terminals and switches.
Innovation Solution
A semiconductor device with a PLL circuit that includes a phase comparison part, voltage conversion part, oscillation part, and correction circuit, where the phase difference signal is outputted through an external terminal for testing, allowing a test control signal to produce a correction current, enabling pulse width evaluation to determine the correction circuit's effectiveness without requiring a switch for external current measurement.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If a switch and external terminal are added to output the correction current for testing, then the testability of the correction circuit is improved, but parasitic capacitance and leakage paths are introduced that deteriorate the properties of the correction circuit during normal operation
Solution Approach 1:
The invention extracts the testing function from the normal operation path by outputting the phase difference signal (which contains information about correction current effectiveness) through a separate external terminal rather than requiring a dedicated switch for correction current output. This allows testing without adding parasitic elements to the correction circuit path.
Solution Approach 2:
The phase difference signal serves as an intermediary that indirectly indicates the effectiveness of the correction current. Instead of directly measuring the correction current (which would require switches and external terminals connected to the correction circuit), the system uses the phase difference signal as a mediator to assess correction circuit performance, thereby avoiding direct connection of test equipment to the correction circuit.
2Measurement precision
If a switch is used to output the correction current during test, then the correction current can be measured externally, but the switch introduces parasitic capacitance and leakage paths that affect normal operation
Solution Approach 1:
The phase difference signal acts as an intermediary indicator that reflects correction current effectiveness without requiring direct measurement of the correction current itself. This eliminates the need for switches and external terminals connected to the correction current path, thereby avoiding parasitic capacitance and leakage issues while still enabling assessment of correction circuit performance.
Solution Approach 2:
The invention replaces the mechanical/electrical switch-based measurement system with a signal-based assessment system. Instead of using a physical switch to route correction current to an external terminal for measurement, the system uses the phase difference signal (an electrical signal already present in the circuit) to indirectly indicate correction current effectiveness, eliminating the need for physical switching mechanisms.
3Measurement precision
If high accuracy current measurement is required for testing the correction current, then accurate assessment of the correction circuit is achieved, but the testing becomes difficult and requires specialized equipment
Solution Approach 1:
The phase difference signal serves as an intermediary measurement parameter that is easier to measure accurately than the correction current itself. By measuring the phase difference signal (which can be done with standard digital logic analysis equipment) rather than directly measuring the correction current (which would require high-precision current measurement equipment), the system achieves accurate assessment of correction circuit performance with simpler, more accessible testing equipment.
Data Source
AI summary
A semiconductor device according to the present invention has a PLL circuit which includes: a phase comparison part that detects the phase difference between a reference signal and an oscillation signal to produce a phase difference signal indicative of the phase difference in binary and then output the produces signal to outside through a first external terminal; a voltage conversion part that applies, to a phase difference voltage node, a phase difference voltage having a voltage value corresponding to the phase difference represented by the phase difference signal; an oscillation part that produces, as an oscillation signal, a signal having a frequency depending on the phase difference voltage; and a correction circuit that supplies a correction current to the phase difference voltage node, and upon reception of a test control signal at a second external terminal, supplies a current depending on the test control signal to the phase difference voltage node as a correction current.