ADP5014ACPZ-R7 datasheet(27/34 Pages) AD

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Data Sheet

ADP5014

Rev. A | Page 27 of 34

DESIGN EXAMPLES

This section provides an example of the step by step design

procedures and the external components required for Channel 1.

Table 12 lists the design requirements for this example.

Table 12. Example Design Requirements for Channel 1

Parameter

Specification

Input Voltage

VPVIN1 = 5 V ± 5%

Output Voltage

VOUT1 = 1.2 V

Output Current

IOUT1 = 4 A

Output Ripple

ΔVOUT1_RIPPLE = 5 mV in CCM mode

Load Transient

±5%, at 20% to 80% load transient, 1 A/µs

Although this example shows step by step design procedures for

Channel 1, the procedures apply to all other buck regulator

channels (Channel 2 to Channel 4).

SETTING THE SWITCHING FREQUENCY

The first step when setting the switching frequency is to determine

the switching frequency for the ADP5014 design. In general,

higher switching frequencies produce a smaller solution size

due to the lower component values required, whereas lower

switching frequencies result in higher conversion efficiency due

to lower switching losses.

The switching frequency of the ADP5014 can be set to a value

from 500 kHz to 2.5 MHz by connecting a resistor from the RT

pin to ground. The selected resistor allows users to make

decisions based on the trade-off between efficiency and solution

size. For more information, see the Oscillator section.

However, the highest supported switching frequency must be

assessed by checking the voltage conversion limitations

enforced by the minimum on time and the minimum off time

(see the Voltage Conversion Limitations section).

In this design example, a switching frequency of 1.2 MHz

achieves a good combination of small solution size and high

conversion efficiency. To set the switching frequency to

1.2 MHz, use the following equation to calculate the resistor

value, RRT:

RRT (kΩ) = (100,000/fSW (kHz))

According to this equation, select standard resistor RRT =

82.5 kΩ.

SETTING THE OUTPUT VOLTAGE

Because the desired output voltage setting is less than VREF

voltage, use the resistor divider from the accurate internal

VREF reference voltage to set the desired output voltage and

directly tie the feedback pin (FB1) to the output (see Figure 38).

Select a 10 kΩ bottom resistor (R2) and then calculate the top

resistor using the following equation:

R1 = R2 × ((VREF − VOUT)/VOUT)

where:

VOUT is the output voltage.

VREF is 2.0 V for Channel 1 to Channel 4.

To set the output voltage to 1.2 V, choose the following resistor

values: R1 = 6.65 kΩ, and R2 = 10 kΩ.

SETTING THE CONFIGUATIONS (CFG1 AND CFG2)

The CFG1 pin can be used to program the load output

capability and parallel operation for all channels. For this

example, choose RCFG1 = 0 kΩ. For more information, see the

configuration in Function Configurations (CFG1 and CFG2).

The CFG2 pin can be used to program the operation mode

(FPWM or PWM/PSM mode), the enable mode (manual mode

or sequence mode), the timer (×1 or ×8), and GPIO functionalities

(PWRGD, SYNC-IN, CLK-OUT, UVO) for all channels. For

this example, choose RCFG2 = 0 kΩ. For more information, see the

configuration in Function Configurations (CFG1 and CFG2).

SELECTING THE INDUCTOR

The peak-to-peak inductor ripple current, ΔIL, is set to 30% of

the maximum output current. Use the following equation to

estimate the value of the inductor (L):

OUT

∆

−

)

(

where:

VIN = 5 V.

VOUT = 1.2 V.

D is the duty cycle (D = VOUT/VIN = 0.24).

ΔIL = 30% × 4 A = 1.2 A.

fSW = 1.2 MHz.

The resulting value for L is 0.63 µH. The closest standard

inductor value is 0.8 µH; therefore, the inductor ripple current,

ΔIL1, is 0.95 A.

The inductor peak current is calculated using the following

equation:

IPEAK = IOUT + (ΔIL/2)

The calculated peak current for the inductor is 4.48 A.

The rms current of the inductor can be calculated using the

following equation:

OUT

RMS

∆

The rms current of the inductor is approximately 4.01 A.

Therefore, an inductor with a minimum rms current rating of

4.01 A and a minimum saturation current rating of 4.48 A is

required. However, to prevent the inductor from reaching its

saturation point in current-limit conditions, it is recommended

that the inductor saturation current be higher than the maximum

peak current limit, typically 6 A, for reliable operation.

Based on these requirements and recommendations, the

COILCRAFT XAL5030-801MEB, with a direct current

resistance (DCR) of 5.14 mΩ, is selected for this design.

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