ADP2360ACPZ-5.0-R7 datasheet(13/16 Pages) AD

13 / 16 page

ADP2360

Data Sheet

Rev. 0 | Page 12 of 15

APPLICATIONS INFORMATION

Compatible components for the step-down application circuits

in Figure 24 and Figure 25 are identified using the guidelines in

this section.

AGND

(EPAD)

VIN

PGND

CIN

COUT

ADP2360

FB 4

ITH 3

VOUT

VIN

OFF

CSS

RPG

RITH

Figure 24. Typical Application Circuit Fixed Output Voltage

AGND

(EPAD)

VIN

PGND

CIN

COUT

ADP2360

FB 4

ITH

VOUT

VIN

OFF

CSS

RPG

RITH

RFB1

RFB2

CFF

Figure 25. Typical Application Circuit Adjustable Output Voltage

SETTING THE OUTPUT VOLTAGE

The ADP2360 is available with 3.3 V and 5.0 V fixed output voltage

options. For the fixed options, an internal resistive feedback divider

sets the output voltage and no external resistors are necessary,

as shown in Figure 24.

The ADP2360 is also available with an adjustable output voltage

and can be configured for output voltages between 0.8 V and

VIN. Use the following equation to determine RFB1 and RFB2 for

the desired VOUT:

FALLING

FB2

FB1

OUT



















(2)

When using an external resistor divider, the optional feedforward

capacitor CFF may be placed across RFB1.

INPUT CAPACITOR SELECTION

An input capacitor must be placed between the VIN pin and

PGND. Ceramic capacitors greater than or equal to 4.7 μF are

recommended. The input capacitor reduces the input voltage

ripple caused by the switching current. Place the input capacitor

as close as possible to the VIN pin to reduce input voltage spikes.

The voltage rating of the input capacitor must be greater than

the maximum input voltage.

ESTIMATING THE SWITCHING FREQUENCY

The ADP2360 switching frequency (fSW) can be estimated with

the following equation:





–

PEAK

OUT





(3)

where the duty cycle, D, is approximated by

OUT

D 

(4)

Note that the switching frequency changes in direct proportion

to the output current. The maximum frequency can be controlled

by the inductor value and the peak current control resistor RITH.

SETTING THE PEAK INDUCTOR CURRENT

The control method of the ADP2360 means that the maximum

output current is slightly less than half of IPEAK. The peak current

limit must be programmed to at least twice the desired

maximum output current.

The value of the selected IPEAK current in the ADP2360 application

affects the efficiency, switching frequency, and output voltage

ripple. Larger IPEAK values tend to give improved efficiency. Using a

smaller IPEAK value gives a higher switching frequency and reduced

output voltage ripple.

The desired peak current limit (IPEAK) is programmed to a discrete

value between 50 mA and 140 mA with an external resistor from

ITH to AGND. This external resistor, RITH, is chosen using the

values in Table 5.

Table 5. Peak Inductor Current Settings

RITH (kΩ)

IPEAK (mA)

Open

1500

825

576

453

365

100

287

120

140

The values given in Table 5 correspond to standard 1% E96

resistor values. A 1% tolerance resistor of the specified value

must be used to ensure the correct IPEAK value is selected. The

IPEAK value set by RITH on the ITH pin is determined upon startup

and is reset only if the device is disabled and reenabled using the

EN pin or a VIN power cycle.

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