OUT

LH

IN

OUT

IN

SW

V

I

L

V

V

V

f

u

u

u

u

)

(

K

(2)

where

• fSW is the switching frequency of the converter

• ILH is the inductor current ripple

• η is the boost converter power convert efficiency

Having selected the inductance value, follow Equation 3 to Equation 5 to calculate the inductor's peak current

for the application. Depending on different load conditions, the TPS61322xx works in continuous current mode

or discontinuous conduction mode(DCM). In different modes, the peak currents of the inductor are also different.

Equation 3 provides an easy way to estimate whether the device works in CCM or DCM. Equation 4 shows the

peak current when the device works in CCM and Equation 5 shows the peak current when the device works in

DCM.

2

LH

IN

OUT

OUT

I

V

I

V

!

u

u

K

(3)

where

• ILH is the inductor current ripple

• η is the boost converter power convert efficiency

2

,

LH

IN

OUT

OUT

peak

L

I

V

I

V

I

u

u

K

(4)

where

• IL,peak is the peak current of the inductor

• ILH is the inductor current ripple

• η is the boost converter power convert efficiency

LH

peak

L

I

I

,

(5)

where

• IL,peak is the peak inductor.

• ILH is the inductor current ripple

The saturation current of the inductor must be higher than the calculated peak inductor current, otherwise the

excessive peak current in the inductor harms the device and reduces the system reliability.

8.2.1.2.4

In this example, the maximum load for the boost converter is 50 mA, the minimum input voltage is 0.9 V, and the

efficiency under this condition can be estimated at 80%, so the boost converter works in continuous operation

mode by the calculation. The inductor peak current is calculated as 258 mA. To have some margin, a 4.7-µH

inductor with at least 300 mA saturation current is recommended for this application. A 10-µH inductor can be

used as well by increasing the output capacitance to higher than 22 µF to make the loop stable. Table 8-2 lists

the recommended inductors for TPS61322xx device.

Table 8-2. List of Inductors

INDUCTAN

CE [µH]

SATURATION CURRENT

[A]

DC

RESISTANC

E [mΩ]

SIZE (L×W×H)(mm)

PART NUMBER

MANUFACTURER(1)

4.7

1.7

165

2.5 × 2 × 1.2

DFE252012P-4R7M=P2

MURATA

4.7

1.5

141

3 × 3 × 1.5

74438335047

Wurth

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TPS61322

SLVSDY5E – JANUARY 2018 – REVISED FEBRUARY 2024

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