ADP2302ARDZ-R7 datasheet(19/28 Pages) AD

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Data Sheet

ADP2302/ADP2303

Rev. A | Page 19 of 28

INPUT CAPACITOR

The input capacitor must be able to support the maximum input

operating voltage and the maximum RMS input current. The

rms ripple current flowing through the input capacitor is, at

maximum, ILOAD(max)/2. Select an input capacitor capable of

withstanding the rms ripple current for an application’s maxi-

mum load current using the following equation:



LOAD

RMS







(max)

)

(

where D is the duty cycle and is equal to

OUT





The recommended input capacitance is ceramic with X5R or X7R

dielectrics due to its low ESR and small temperature coefficients.

A capacitance of 10 μF should be adequate for most applications.

To minimize supply noise, place the input capacitor as close as

possible to the VIN pin of the ADP2302/ADP2303.

OUTPUT CAPACITOR

The output capacitor selection affects both the output voltage ripple

and the loop dynamics of the regulator. The ADP2302/ADP2303

are designed to operate with small ceramic capacitors that have

low ESR and equivalent series inductance (ESL) and are, therefore,

easily able to meet stringent output voltage ripple specifications.

When the regulator operates in continuous conduction mode,

the overall output voltage ripple is the sum of the voltage spike

caused by the output capacitor equivalent series resistance

(ESR) plus the voltage ripple caused by the charging and

discharging of the output capacitor























OUT

RIPPLE

ESR

Capacitors with lower ESR are preferable to guarantee low

output voltage ripple, as shown in the following equation:

RIPPLE

Cout

ESR





Ceramic capacitors are manufactured with a variety of dielec-

trics, each with different behavior over temperature and applied

voltage. X5R or X7R dielectrics are recommended for best

performance, due to their low ESR and small temperature

coefficients. Y5V and Z5U dielectrics are not recommended

because of their poor temperature and dc bias characteristics.

In general, most applications require a minimum output

capacitor value of 2 × 22 μF.

Some recommended output capacitors for VOUT ≤ 5.0 V are

provided in Table 9.

THERMAL CONSIDERATION

ADP2302/ADP2303 have an internal high-side MOSFET and

its drive circuit. Only a small amount of power dissipates inside

the ADP2302/ADP2303 package under typical load conditions,

which reduces thermal constraints.

However, in applications with maximum loads at high ambient

temperature and high duty cycle, the heat dissipated in the

package may cause the junction temperature of the die to

exceed the maximum junction temperature of 125°C. If the

junction temperature exceeds 150°C, the regulator goes into

thermal shutdown and recovers when the junction temperature

drops below 135°C.

The junction temperature of the die is the sum of the ambient

temperature and the temperature rise of the package due to

power dissipation, as indicated in the following equation:

TJ = TA + TR

where:

TJ is the junction temperature.

TA is the ambient temperature.

TR is the rising temperature of the package due to power

dissipation.

The rising temperature of the package is directly proportional

to the power dissipation in the package. The proportionality

constant for this relationship is the thermal resistance from the

junction of the die to the ambient temperature, as shown in the

following equation:

TR = θJA × PD

where:

TR is the rising temperature of the package.

θJA is the thermal resistance from the junction of the die to the

ambient temperature of the package.

PD is the power dissipation in the package.

Table 9. Recommended Capacitors for VOUT ≤ 5.0 V

Vendor

Value

Part No.

Dimensions L × W × H (mm)

Murata

22 μF, 6.3 V, X5R

GRM31CR60J226KE19

3.2 × 2.5 × 2.0

47 μF, 6.3 V, X5R

GRM32ER60J476ME20

3.2 × 2.5 × 2.0

TDK

22 μF, 6.3 V, X5R

C3216X5R0J226MB

3.2 × 1.6 × 0.85

33 μF, 6.3 V, X5R

C3216X5R0J336MB

3.2 × 1.6 × 1.3

47 μF, 6.3 V, X5R

C3225X5R0J476MB

3.2 × 2.5 × 2.5

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