TS4621ML datasheet(27/40 Pages) STMICROELECTRONICS

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TS4621ML

Application information

Doc ID 023181 Rev 1

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4.3

External component selection

The TS4621ML requires few external passive components to operate correctly. Each

component is described in the following sections.

4.3.1

Step-down inductor selection (L1)

The TS4621ML needs one inductor for the internal step-down DC/DC converter. This

inductor must fit the following constraints:

●

Typical value: 2.2 µH to 3.3 µH (3.3 µH is recommended)

●

Maximum current in operating mode: 400 mA

●

Minimum inductor value at maximum current: 1.5 µH

●

Maximum inductor value at zero current: 4.3 µH

●

DC resistance: from 50 m

Ω up to 450 mΩ

Table 6 shows the part number that should be used according to the inductor value.

4.3.2

Step-down output capacitor selection (Ct)

For the internal DC/DC step-down converter, the TS4621ML needs one output capacitor.

The three criteria for selecting the output capacitor are the range value of the capacitor

including self tolerance, DC variation and the minimum ESR value, which is mandatory to

avoid oscillation of the converter. Therefore the following constraints must be observed.

●

Typical capacitor value: 10 µF at DC = 0 V

●

Maximum capacitor value: 12 µF at DC = 0 V

●

Minimum capacitor value: 4.8 µF at DC = 2 V

●

Voltage range across this capacitor: from 1.1 V to 2 V

●

Minimum DC ESR value: 5 m

A ceramic capacitor in a 0603-type package is also recommended because of its close

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

resistance that have a negative impact on the audio performance.

Table 6.

Recommended inductor

Manufacturer

Part number

Value

Murata

LQM21PN3R3NGRD

3.3 µH

LQM2MPN3R3G0L

3.3 µH

LQM2MPN2R2G0L

2.2 µH

FDK

MIPSZ2012D3R3

3.3 µH

MIPSZ2012D2R2

2.2 µH

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