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Data Sheet

ADP2300/ADP2301

Rev. C | Page 19 of 28

CATCH DIODE

The catch diode conducts the inductor current during the off

time of the internal MOSFET. The average current of the diode

in normal operation is, therefore, dependent on the duty cycle

of the regulator as well as the output load current.

(max)

)

(

LOAD

OUT

AVG

DIODE













−

where VD is the diode forward drop.

The only reason to select a diode with a higher current rating than

necessary in normal operation is for the worst-case condition, in

which there is a shorted output. In this case, the diode current

increases up to the typical peak current-limit threshold. Be sure to

consult the diode data sheet to ensure that the diode can operate

well within the thermal and electrical limits.

The reverse breakdown voltage rating of the diode must be higher

than the highest input voltage and allow an appropriate margin

for the ringing that may be present on the SW node. A Schottky

diode is recommended for best efficiency because it has a low

forward voltage drop and fast switching speed. Table 8 provides

a list of recommended Schottky diodes.

Table 8. Recommended Schottky Diodes

Vendor

Part No.

RRM

(V)

AVG

(A)

ON Semiconductor

MBRS230LT3

MBRS240LT3

Diodes Inc.

B230A

B240A

Vishay

SL23

SS24

INPUT CAPACITOR

The input capacitor must be able to support the maximum input

operating voltage and the maximum rms input current. The

maximum rms input current flowing through the input

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

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

mum load current using the following equation:

)

(

(max)

)

(

LOAD

RMS

−

where D is the duty cycle and is equal to

OUT

The recommended input capacitor 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 to

the VIN pin of the ADP2300/ADP2301 as possible.

OUTPUT CAPACITOR

The output capacitor selection affects both the output voltage ripple

and the loop dynamics of the regulator. The ADP2300/ADP2301

are designed to operate with small ceramic capacitors that have low

equivalent series resistance (ESR) and equivalent series inductance

(ESL) and are, therefore, easily able to meet stringent output voltage

ripple specifications.

When the regulator operates in forced continuous conduction

mode, the overall output voltage ripple is the sum of the voltage

spike caused by the output capacitor ESR plus the voltage ripple

caused by charging and discharging 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

ESR

OUT

∆

≤

Ceramic capacitors are manufactured with a variety of dielectrics,

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 using the ADP2301 (1.4 MHz

switching frequency) require a minimum output capacitor value

of 10 µF, whereas most applications using the ADP2300 (700 kHz

switching frequency) require a minimum output capacitor value

of 20 µF. Some recommended output capacitors for VOUT ≤ 5.0 V

are listed in Table 9.

Table 9. Recommended Capacitors for VOUT ≤ 5.0 V

Vendor

Value

Part No.

Dimensions

L × W × H (mm)

Murata

10 µF, 6.3 V

GRM31MR60J106KE19

3.2 × 1.6 × 1.15

22 µF, 6.3 V

GRM31CR60J226KE19

3.2 × 1.6 × 1.6

TDK

10 µF, 6.3 V

C3216X5R0J106K

3.2 × 1.6 × 1.6

22 µF, 6.3 V

C3216X5R0J226M

3.2 × 1.6 × 0.85

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