R5975D datasheet(35/47 Pages) STMICROELECTRONICS

Part #	R5975D

Description	Up to 3 A step-down switching regulator for aerospace applications

PDF	47 Pages

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Manufacturer	STMICROELECTRONICS [STMicroelectronics]

Direct Link	http://www.st.com

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35 / 47 page

DocID026878 Rev 1

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R5975D

Application information

Figure 21. Short-circuit current VIN = 36 V

8.6

Positive buck-boost regulator

The device can be used to implement a step-up/down converter with a positive output

voltage.

The output voltage is given by:

Equation 37

where the ideal duty cycle D for the buck-boost converter is:

Equation 38

However, due to power losses in the passive elements, the real duty cycle is always higher

than this. The real value (that can be measured in the application) should be used in the

following formulas.

The peak current flowing in the embedded switch is:

Equation 39

VOUT

VIN

–

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



VOUT

VIN VOUT

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

ISW

ILOAD

–

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

IRIPPLE

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

ILOAD

–

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

VIN



-----------

fSW

---------



R5975D Datasheet(PDF) 35 Page - STMicroelectronics

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