TS4621ML datasheet(28/40 Pages) STMICROELECTRONICS

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Application information

TS4621ML

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Doc ID 023181 Rev 1

4.3.3

Full capacitive inverter capacitors selection (C12 and CSS)

Two capacitors (C12 and Css) are needed for this internal DC/DC inverter.

The three criteria for selecting these capacitors are the range value of the capacitor

including self tolerance, DC variation and the minimum ESR to minimize power losses.

●

Typical capacitor value: 2.2 µF +/-20 %

●

Voltage across these capacitors: from 1.1 V to 2 V

●

Minimum capacitor value: 1 µF

Again, a ceramic capacitor in a 0603 or 0402-type package is also recommended because

of their close placement to the TS4621ML, which makes it easier to minimize parasitic

inductance and resistance that have a negative impact on the audio performance.

4.3.4

Power supply decoupling capacitor selection (Cs)

A 2.2 µF decoupling capacitor with low ESR is recommended for positive power supply

decoupling. Packages such as the 0402 or 0603 are also recommended because of their

close placement to the TS4621ML, which makes it easier to minimize parasitic inductance.

It is advised to choose a X5R dielectric for capacitor tolerance, and a 10 V DC rating voltage

for 4.8 V operations (or a 6.3 V DC rating voltage for 3.6 V operations), to take into

consideration the

ΔC/ΔV variation of this type of ceramic capacitor.

An important parameter is the rated voltage of the capacitor. A 2.2 µF/6.3 V capacitor used

at 4.8 V DC typically loses about 40 % of its value. In fact, with a 4.8 V power supply voltage,

the decoupling value is about 1.3 µF instead of 2.2 µF. Because the decoupling capacitor

influences the THD+N in the medium-to-high frequency region, this capacitor variation

becomes decisive. In addition, less decoupling means higher overshoots, which can be

problematic if they reach the power supply’s AMR value (5.5 V). This is why, for a 2.2 µF

value, we recommend a 2.2 µF/10 V, a 4.7 µF/6.3 V or a ceramic capacitor with a low DC

bias variation rated at 6.3 V.

4.3.5

Input coupling capacitor selection (Cin)

Cin input coupling capacitors are mandatory for the TS4621ML’s operation. They block any

DC component coming from the audio signal source.

Cin with Rin form a first-order high-pass filter and the -3 dB cut-off frequency is:

Rin is the single-ended input impedance that can be approximated at about Rindiff/2.

Rin also depends on the gain setting. Figure 10 provides the differential input impedance vs.

gain. One can also see that Rindiff is minimum for the maximum gain setting (that is, 6 dB).

Table 7.

Recommended capacitors

Manufacturer

Part number

Value

Murata

GRM188R60J106ME47

10 µF, 6.3 V, X5R

GRM188R60J106ME84

10 µF, 6.3 V, X5R

GRM188R61E106ME73

10 µF, 25 V, X5R

3dB

–

()

π Rin Cin

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