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    5. MLCCs: An Alternative solution, for Smartphone applications, instead of Tantalum Capacitor

    Ceramic Capacitor/Application SupportMLCCs: An Alternative solution, for Smartphone applications, instead of Tantalum Capacitor

    Tantalum capacitors are often used as the capacitor connected to the power line of PA(=Power Amplifier) for GSM on smart phones. In this report, we evaluate replacing the tantalum capacitor (Ta-Cap) with a ceramic capacitor.

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    1Target capacitor

    We purchased a smartphone and evaluated it. The circuit of the battery line, which is the analysis of our own, is shown in the figure below. A Ta-Cap is connected near the power line of the PA for GSM.

    The circuit of the battery line

    2Proposal of replacement

    The proposal is illustrated below. We selected the low acoustic noise Ceramic capacitor “ZRB series” as replacement. As you can see, the mounting space is reduced by 50%.

    ＜ Proposal ＞

    C1：Ta-Cap 100uF/1206size x 1pcs → Low acoustic noise ceramic capacitor 22uF/6.3V/0603size x 2pcs

    Proposal of replacement

    3Evaluation for replacement

    We measured the following properties before and after replacement.

    Evaluation for replacement

    1）Communication characteristics

    The value of the capacitor that is connected to the PA power line affects signal quality. Therefore, it is necessary to test the communication characteristics.

    2) Voltage fluctuation

    If the impedance of the power line changes, noise will change. Therefore, it is necessary to test the power line voltage fluctuations of the PA.

    3) Acoustic evaluation

    The PA for GSM is operated by a burst audible frequency (217Hz) cycle. Therefore, an evaluation of acoustic noise is required.

    4Communication characteristics and voltage fluctuation

    Communication characteristics and voltage fluctuation were tested by the measurement system below.

    Communication characteristics and voltage fluctuation

    Communication characteristics(1)

    ＜GSM850MHz GSM900MHz mode＞

    < GSM850MHz and GSM900MHz mode >

    The communication characteristics meet the standard for GSM!

    Communication characteristics(2)

    ＜GSM1800MHz GSM1900MHz mode＞

    < GSM1800MHz and GSM1900MHz mode >

    The communication characteristics meet the standard for GSM!

    Voltage fluctuation(1)

    ＜GSM850MHz mode and GSM900MHz mode＞

    << Voltage fluctuation >> GSM850MHz mode and GSM900MHz mode

    The noise of power line is reduced 7–8%.

    Voltage fluctuation(2)

    ＜GSM1800MHz mode and GSM1900MHz mode＞

    << Voltage fluctuation >> GSM1800MHz mode and GSM1900MHz mode

    The noise of power line is reduced 14–22%. 

    5Evaluation of acoustic noise

    Acoustic noise is measured as sound pressure level (SPL) by the measurement system below.

    Evaluation of acoustic noise
    Evaluation of acoustic noise_Initial (Ta-Cap) vs. proposal (ZRB series)

    SPL is equal to the initial. (There is no significant difference.)

    6Summary of evaluation

    We evaluated replacing the Ta-Cap that is connected to the power line of the PA for GSM with a ceramic capacitor. In the evaluation, we tested (1) the communication characteristics, (2) the voltage fluctuation, and (3) acoustic noise.

    1）Communication characteristics

    The communication characteristics are equal to the initial and meet the standard for GSM.

    2) Voltage fluctuation

    Voltage fluctuation is reduced 7–22%.

    3) Evaluation of acoustic noise

    Acoustic noise level is equal to the initial.

    7Merits of using ceramic capacitors

    Advantages of replacing the Ta-Cap with a ceramic capacitor

    Merits of using ceramic capacitors

    < Impedance characteristics of Ta-Cap 100uF vs ceramic capacitor 22uF >

    Impedance characteristics of Ta-Cap 100uF vs ceramic capacitor 22uF

    Ceramic capacitors have low ESR and low ESL characteristics. Therefore, the impedance of a ceramic capacitor (22uF/6.3V/0603size) is smaller than that of a Ta-Cap (100uF/6.3V/1206size) over 100kHz range. Thus, the ceramic capacitor has a better noise suppression effect at a high-frequency range.

    < Ripple current – Self heating characteristics >

    Ripple current – Self heating characteristics

    Temp. rise level is lower than Ta-Cap. due to low ESR.

    < Breakdown Voltage Characteristics >

    Breakdown Voltage Characteristics

    Ceramic capacitors have high breakdown voltage.

    8Summary

    We demonstrated the evaluation result of replacing the Ta-Cap with a ceramic capacitor, and the benefits of using a ceramic capacitor.

    Evaluation for replacement

    • Voltage fluctuation is reduced 7–22%. 
    • The communication characteristics are equal to the initial and meet the standard for GSM. 
    • Acoustic noise level is equal to the initial.

    Benefits of using a ceramic capacitor

    • Ceramic capacitors have good performance for noise suppression because the ESR and ESL of ceramic capacitors are lower than Ta-Cap.
    • Ceramic capacitor has low temperature rise performance because the ESR of ceramic capacitors is lower than Ta-Cap.
    • Breakdown voltage of ceramic capacitors is higher than Ta-Cap.

    Proposal

    C1: Ta-Cap 100uF/1206size x 1pcs → Low acoustic noise Ceramic capacitor 22uF/6.3V/0603size x 2pcs

    Replacement parts number: ZRB18AR60J226ME01

    Contact your local Murata sales rep for further support.

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    5. MLCCs: An Alternative solution, for Smartphone applications, instead of Tantalum Capacitor
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