Application Support

MLCCs: 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.
*Click to jump to each item
     
 

1. Target capacitor

2. Proposal of replacement

3. Evaluation for replacement

4. Communication characteristics and voltage fluctuation

5. Evaluation of acoustic noise

6. Summary of evaluation

7. Merits of using ceramic capacitors

8. Summary


SubTitleIconNo01 Target 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

SubTitleIconNo02 Proposal 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


SubTitleIconNo03 Evaluation 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.


SubTitleIconNo04 Communication 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%. 

 


SubTitleIconNo05 Evaluation 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.)


SubTitleIconNo06 Summary 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.

SubTitleIconNo07 Merits 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.

SubTitleIconNo08 Summary


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.