MB39C014 datasheet(15/32 Pages) CYPRESS

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Document Number: 002-08361 Rev. *C

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MB39C014

10.2 Output Voltage Setting

The output voltage VOUT of this IC is defined by the voltage input to VREFIN. Supply the voltage for inputting to VREFIN from an

external power supply, or set the VREF output by dividing it with resistors.

The output voltage when the VREFIN voltage is set by dividing the VREF voltage with resistors is shown in the following formula.

Note :

Refer to “Application Circuit Examples” for an example of this circuit.

Although the output voltage is defined according to the dividing ratio of resistance, select the resistance value so that the current

flowing through the resistance does not exceed the VREF current rating (1 mA) .

10.3 About Conversion Efficiency

The conversion efficiency can be improved by reducing the loss of the DC/DC converter circuit.

The total loss (PLOSS) of the DC/DC converter is roughly divided as follows :

PLOSS

= PCONT + PSW + PC

PCONT

: Control system circuit loss (The power used for this IC to operate, including the gate driving power for internal SW

FETs)

PSW

: Switching loss (The loss caused during switching of the IC's internal SW FETs)

: Continuity loss (The loss caused when currents flow through the IC's internal SW FETs and external circuits )

The IC's control circuit loss (PCONT) is extremely small, less than 100 mW with no load.

As the IC contains FETs which can switch faster with less power, the continuity loss (PC) is more predominant as the loss during heavy-

load operation than the control circuit loss (PCONT) and switching loss (PSW) .

VOUT

= 2.97 × VREFIN,

VREFIN

× VREF

+ R4

(VREF

= 1.20 V)

VREF

VREFIN

VREF

VREFIN

MB39C014

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