Browse Prior Art Database

Shoot-Through-Current-Free Ring-Oscillator for Accurate Capacitance Measurement

IP.com Disclosure Number: IPCOM000223646D
Publication Date: 2012-Nov-20
Document File: 5 page(s) / 189K

Publishing Venue

The IP.com Prior Art Database

Abstract

Disclosed is a method to measure the cap value of a capacitive load and obtain the accurate Cload readout given the Ring-Oscillator derived ΔCeff parameter value. The approach is to purpose a novel Ring-Oscillator structure to eliminate the shoot-through current during switching transition, and to get an accurate capacitance measurement that is insensitive to the number of Ring-stages, the Vdd bias, and the series resistance value of the Cload under test.

This text was extracted from a PDF file.
This is the abbreviated version, containing approximately 52% of the total text.

Page 01 of 5

Shoot-Through-Current-Free Ring-Oscillator for Accurate Capacitance Measurement

It is a common practice to measure the cap value of a capacitive load using Ring-oscillator. The purpose is to have the measured ΔCeff equals the real Cap value. However, the observed ΔCeff value is either higher or lower than the expected real cap value, and observed ΔCeff is a non-monotonic function of Frequency, which is modulated by changing the Vdd power supply. This makes it difficult to measure the accurate Cload value with the derived Ring Ceff parameter. Furthermore, the frequency dependency of Cload is inferred by hw observed Ceff(Vdd) dependency. One solution is needed by which to obtain the accurate Cload readout given the Ring-Oscillator derived ΔCeff parameter value.

Figures 1 and 2 illustrate the problem. The TSV or any other cap load has unknown cap and series resistance value.

Figure 1: Illustration of the problem

Ceff = 2*(Idda-Iddq)*Delay/Vdd;

ΔCeff = Ceff_loaded-Ceff_unloaded

Figure 2: Illustration of the problem

1


Page 02 of 5

There is no hardware (HW) solution available so far to obtain an accurate capacitance measurement using Ring-Oscillator.

Two possible causes for the opposite Ceff(Vdd) dependency are:
 Shoot-through current, which causes higher Ceff

 Too-fast cycle, which causes lower Ceff


The interaction of both effects makes non-monotonic Ceff vs. Vdd response, which makes accurate capacitance measurement difficult.

Figure 3: Cause: Shoot-Through Current Through the Inverter

The proposed solution is to purpose a novel Ring-Oscillator structure to eliminate the

2


Page 03 of 5

shoot-through current during switching transition, and to get an accurate capacitance measurement that i...