Datasheet
Data Sheet ADP2118
Rev. C | Page 17 of 24
The ADP2118 has integrated loop compensation for simple
power design. Table 5 and Table 6 show the typical recom-
mended inductors and capacitors for the ADP2118. X5R or X7R
ceramic capacitors are highly recommended.
Table 5. Recommended L and C
OUT
Value at f
S
= 1.2 MHz
V
IN
(V) V
OUT
(V) L (μH) C
OUT
(μF)
3.3 1.0 1 100 + 47
3.3 1.2 1 100
3.3 1.5 1 100
3.3 1.8 1 100
3.3 2.5 1 100
5 1.0 1 100 + 47
5 1.2 1 100
5 1.5 1 100
5 1.8 1 100
5 2.5 1 100
5 3.3 1 100
Table 6. Recommended L and C
OUT
Value at f
S
= 600 kHz
V
IN
(V) V
OUT
(V) L (μH) C
OUT
(μF)
3.3 1.0 1.5 100 + 47
3.3 1.2 1.5 100
3.3 1.5 1.5 100
3.3 1.8 1.5 100
3.3 2.5 1.5 100
5 1.0 1.5 100 + 47
5 1.2 1.5 100
5 1.5 2.2 100
5 1.8 2.2 100
5 2.5 2.2 100
5 3.3 2.2 100
Higher or lower inductors and output capacitors can be used in
the regulator, but the system stability and load transient
performance need to be checked.
The minimum output capacitor can be 47 μF. If f
S
= 1.2 MHz,
the inductor range is 0.8 μH to 3.3 μH. If f
S
= 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:
DDII
ORMS
1
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 R
TRKT
= R
TOP
and R
TRKB
= R
BOT
.
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
R
R
R
R
V
V
1
1
08301-005
V
MASTER
V
SLAVE
R
TOP
R
BOT
R
TRKT
R
TRKB
TRK
FB
ADP2118
Figure 42. Voltage Tracking
08301-006
VOLTAGE
TIME
V
MASTER
V
SLAVE
Figure 43. Coincident Tracking
08301-007
TIME
V
MASTER
V
SLAVE
VOLTAGE
Figure 44. Ratiometric Tracking