ADP2118 datasheet(17/24 Pages) AD

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ADP2118

Rev. 0 | Page 17 of 24

Table 6. Recommended L and COUT Value at fS = 600 kHz

VIN (V)

VOUT (V)

L (μH)

COUT (μF)

3.3

1.0

1.5

100 + 47

3.3

1.2

1.5

100

3.3

1.5

100

3.3

1.8

1.5

100

3.3

2.5

1.5

100

1.0

1.5

100 + 47

1.2

1.5

100

1.5

2.2

100

1.8

2.2

100

2.5

2.2

100

3.3

2.2

100

Higher or lower inductors and output capacitors can be used in

the converter, but the system stability and load transient

performance need to be checked.

The minimum output capacitor can be 47 μF. If fS = 1.2 MHz,

the inductor range is 0.8 μH to 3.3 μH. If fS = 600 kHz, the

inductor range is 1.5 μH to 3.3 μH.

Table 7. Recommended Inductors

Manufacturer

Part Number

Coilcraft

MSS1038, MSS1048, MSS1260

Sumida

CDRH103R, CDRH104R, CDRH105R

Table 8. Recommended Capacitors

Manufacturer

Part Number

Description

Murata

GRM32ER60J107ME20

100 μF, 6.3 V, X5R, 1210

Murata

GRM32ER60J476ME20

47 μF, 6.3 V, X5R, 1210

TDK

C3225X5R0J107M

100 μF, 6.3 V, X5R, 1210

TDK

C3225X5R0J476M

47 μF, 6.3 V, X5R, 1210

INPUT CAPACITOR SELECTION

The input capacitor reduces the input voltage ripple caused by

the switch current on PVIN. Place the input capacitor as close

as possible to the PVIN pin. A 22 μF or 47 μF ceramic capacitor

is recommended. The rms current rating of the input capacitor

should be larger than the following equation:



RMS







VOLTAGE TRACKING

The ADP2118 includes a tracking feature that allows the

ADP2118 output (slave voltage) to be configured to track an

external voltage (master voltage), as shown in Figure 42.

A common application is coincident tracking, shown in Figure 43.

Coincident tracking limits the slave output voltage to be the

same as the master voltage until it reaches regulation. Connect

the TRK pin to a resistor divider from the master voltage. For

coincident tracking, set RTRKT = RTOP and RTRKB = RBOT.

Ratiometric tracking is shown in Figure 44. The slave output is

limited to a fraction of the master voltage. In this application,

the slave and master voltages reach the final value at the same

time. The ratio of the slave output voltage to the master voltage

is a function of the two dividers.

TRKB

TRKT

BOT

TOP

MASTER

SLAVE





VMASTER

VSLAVE

RTOP

RBOT

RTRKT

RTRKB

TRK

ADP2118

Figure 42. Voltage Tracking

TIME

VMASTER

VSLAVE

Figure 43. Coincident Tracking

TIME

VMASTER

VSLAVE

Figure 44. Ratiometric Tracking

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