decrease by a specific percentage. This can vary by 10% to 35%. Inductance is also affected by dc current and

temperature.

10.2.1.2.1.1 Inductor Equations

Inductor current rating is determined by the requirements of the load. The inductance is determined by two

factors: the minimum value required for stability and the maximum ripple current permitted in the application.

Use Equation 1 to determine the required current rating. Equation 1 shows the approximate relationship between

90% of its initial inductance value at this current.

L

PVDD

PVDD

I

= I

VBAT

0.8

æ

ö

´ ç

÷

´

è

ø

(1)

CAUTION

Use a minimum working inductance of 1.3 μH. Lower values may damage the inductor.

Use a minimum working inductance of 1.3 μH. Lower values may damage the inductor.

inductor and reduces the potential for EMI. Use Equation 2 to determine the value of the inductor, L. Equation 2

maximum acceptable ripple current into Equation 2 and solve for L.

L

BOOST

VBAT

(PVDD

VBAT)

L =

I

PVDD

´

-

D

´ ¦

´

(2)

inductance to reduce the ripple current. Do not use greater than 4.7 μH, as this prevents the boost converter

from responding to fast output current changes properly. If using above 3.3 µH, then use at least 10 µF

capacitance on PVOUT to ensure boost converter stability.

The typical inductor value range for the TPA2015D1 is 2.2 μH to 3.3 µH. Select an inductor with less than 0.5 Ω

dc resistance, DCR. Higher DCR reduces total efficiency due to an increase in voltage drop across the inductor.

Table 10-2. Sample Inductors

L

(μH)

SUPPLIER

COMPONENT CODE

SIZE

(L×W×H mm)

DCR TYP

(mΩ)

(A)

C RANGE

2.2

Chilisin

Electronics Corp.

CLCN252012T-2R2M-N

2.5 x 2.0 x 1.2

105

1.2

4.7 – 22 µF / 16 V

6.8 – 22 µF / 10 V

2.2

Toko

1239AS-H-2R2N=P2

2.5 × 2.0 × 1.2

96

2.3

2.2

Coilcraft

XFL4020-222MEC

4.0 x 4.0 x 2.15

22

3.5

3.3

Toko

1239AS-H-3R3N=P2

2.5 × 2.0 × 1.2

160

2.0

10 – 22 µF / 10 V

3.3

Coilcraft

XFL4020-332MEC

4.0 x 4.0 x 2.15

35

2.8

10.2.1.2.2 Boost Converter Capacitor Selection

The value of the boost capacitor is determined by the minimum value of working capacitance required for

stability and the maximum voltage ripple allowed on PVDD in the application. Working capacitance refers to the

available capacitance after derating the capacitor value for DC bias, temperature, and aging.

Do not use any component with a working capacitance less than 4.7 μF. This corresponds to a 4.7 µF / 16 V

capacitor, or a 6.8 µF / 10 V capacitor. Do not use above 22 µF capacitance as it will reduce the boost converter

response time to large output current transients.

TPA2015D1

SLOS638C – NOVEMBER 2011 – REVISED JUNE 2022

www.ti.com

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