How to measure capacity versus bias voltage on MLCCs: Page 4 of 4

January 16, 2015 //By Fons Janssen
How to measure capacity versus bias voltage on MLCCs
Fons Janssen, Principal Member of Technical Staff, Maxim Integrated explains how to measure capacity versus bias voltage on MLCCs.
of the bias voltage.
 
A second measurement was performed, now using a known 2.2µF/16V capacitor taken from a sample kit supplied by Murata (part number = GRM188R61C225KE15). In this measurement the values were recorded over the entire operating 0V to 16V range. The relative capacitance was determined by measuring both the output voltage of the circuit and the actual oscillation period. Additionally, data was collected from the Murata® Simsurfing tool, which can provide the DC bias characteristic for this particular part based on measurements performed by Murata. Figure 6 shows all the results. Both graphs with our measurement data show almost identical results, which proves that the time-to-voltage circuit performs well over a larger dynamic range. There is some difference between the data from the Simsurfing tool and our measurements, but the shapes of the curves are similar.
        


Figure 6. Relative capacity as a function of bias voltage for a 2.2µF/16V MLCC. The values are normalized to the capacitance at 0V bias. The blue curve is based on measuring the output voltage of the circuit; the red curve is based on the measurement of the oscillation period; the green curve is based on characterization data supplied by the Murata Simsurfing tool.


Conclusion

Using the presented circuit, a dual power supply, and a voltmeter it is quite simple to measure the DC bias characteristic of a high-capacity MLCC. A quick bench test will reveal how much the capacitance decreases as a result of the applied bias voltage.

Reference
 
[1]        Fortunato, Mark, “Temperature and Voltage Variation of Ceramic Capacitors,” EDN, December 4, 2012, https://www.techonline.com/electrical-engineers/education-training/tech-papers/4410874/Temperature-and-Voltage-Variation-of-Ceramic-Capacitors. Also found as Maxim Integrated application note 5527, “Fortunato, Mark, Temperature and Voltage Variation of Ceramic Capacitors, or Why Your 4.7µF Capacitor Becomes a 0.33µF Capacitor,” https://www.maximintegrated.com/AN5527.

Murata is a registered trademark of Murata Manufacturing Co., Ltd.

The author wishes to thank his colleagues Mark Fortunato and Kuo-Chang Chan for their technical assistance.

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