7

Application information

The DCP3601 is a buck DC-to-DC converter. It is typically used to convert a higher input voltage to a lower output

DC voltage with a maximum output current of 1 A. The following design procedure can be used to select

components for the DCP3601.

7.1

Typical application

The device only requires a few external components to convert from a wide voltage range supply to a fixed output

voltage. The figure below shows a basic schematic.

Figure 4. DCP3601 application schematic

7.2

Output voltage setting

The error amplifier reference voltage is 0.85 V typical (refer to Table 7). The output voltage is adjusted accordingly

with the following equation:

VOUT=0.85∙ 1+R1R2

(8)

7.3

Input capacitor selection

The input capacitor voltage rating must be higher than the maximum input operating voltage of the application.

During the switching activity a pulsed current flows into the input capacitor, and so its RMS current capability must

be selected according to the application conditions. Internal losses of the input filter depend on the ESR value, so

low ESR capacitors (such as multilayer ceramic capacitors) usually have a higher RMS current capability. On the

other hand, given the RMS current value, a lower ESR input filter has lower losses and so contributes to higher

conversion efficiency.

The maximum RMS input current, flowing through the capacitor, can be calculated as follows:

IRMS=IOUT∙ 1−Dη Dη

(9)

Where IOUT is the maximum DC output current, D is the duty cycles, η is the efficiency. This function has a

maximum at D = 0.5 and, considering η = 1, it is equal to IOUT/2. In a specific application, the range of possible

duty cycles has to be considered in order to find out the maximum RMS input current. The maximum and

minimum duty cycles can be calculated as:

DMAX= VOUT+ΔVLOW_side

VIN_min+ΔVLOW_side−ΔVHIGH_side

(10)

DMIN= VOUT+ΔVLOW_side

VIN_max+ΔVLOW_side−ΔVHIGH_side

(11)

DCP3601

Application information

DS14782 - Rev 1

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