PM6685 datasheet(34/52 Pages) STMICROELECTRONICS

34 / 52 page

Monitoring and protections

PM6685

34/52

Equation 10

where fsw is the switching frequency, VIN is the input voltage, VOUT is the output voltage

and

∆IL is the selected inductor ripple current.

In order to prevent overtemperature working conditions, inductor must be able to provide an

RMS current greater than the maximum RMS inductor current ILRMS:

Equation 11

Where

∆IL(max) is the maximum ripple current:

Equation 12

If hard saturation inductors are used, the inductor saturation current should be much greater

than the maximum inductor peak current Ipeak:

Equation 13

Using soft saturation inductors it’s possible to choose inductors with saturation current limit

nearly to Ipeak.

Below there is a list of some inductor manufacturers.

Table 11.

Inductor manufacturer

Manufacturer

Series

Inductor value (uH)

RMS current (A)

Saturation current (A)

COILCRAFT

SER1360

4 to 8

6 to 8.6

7 to 12

COILCRAFT

MLC

2.2 to 4.5

13.6 to 8.8

11.5 to 17

TDK

RLF12560

2.7 to 10

7.5 to 11.5

7.5 to 14.4

OUT

∆

−

(max))

(

(max))

(

LOAD

LRMS

∆

max

OUT

max

(max)

−

∆

(max)

Ipeak

LOAD

∆

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