UM1685 datasheet(27/31 Pages) STMICROELECTRONICS

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UM1685

Sensing resistors of the EVAL6482H

The output current range of the board is determined by the sensing resistors as indicated in

Equation 2 and Equation 3:

Equation 2

Ipeak,min = 7.8 mV / Rsense

Equation 3

Ipeak,max = 1 V / Rsense

Where 7.8 mV and 1 V are the minimum and the maximum value of the TVAL registers.

However the actual output current is usually limited by the power rating of the sensing

resistors:

Equation 4

Note:

The power rating of the sensing resistor determining the maximum output current is 50% of

the nominal one.

If the operative range resulting from the sensing resistors which are mounted on the board

is not suitable for the application, it is possible to change these components in order to fit the

requirements.

The sensing resistors should make the current control to operate with a peak reference

voltage between 0.2 and 0.1 volts. This way the power dissipation on the sensing resistor is

not excessive and the offset of the sensing circuitry does not affect the performance of the

current control algorithm.

Equation 5

Rsense = 0.2 V / Ipeak

Iout limit



Pdmax



Rsense

------------------

(r.m.s. value)

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