Datasheet

ADP1610
Rev. A | Page 14 of 20
Table 5. Recommended External Components for Popular Input/Output Voltage Conditions
V
IN
(V) V
OUT
(V) F
SW
(MHz) L (μH) C
OUT
(μF) C
IN
(μF) R1 (kΩ) R2 (kΩ) R
COMP
(kΩ) C
comp
(pF) I
OUT_MAX
(mA)
3.3 5 0.700 4.7 22 22 30.9 10 68 150 600
5 1.23 2.7 10 22 30.9 10 100 100 600
9 0.700 10 10 10 63.4 10 20 680
350
9 1.23 4.7 4.7 10 63.4 10 47 150
350
10 0.700 10 10 10 71.5 10 33 470
300
10 1.23 4.7 4.7 10 71.5 10 39 220
300
12 0.700 10 10 10 88.7 10 33 470
250
12 1.23 4.7 10 10 88.7 10 75 150
250
5 9 0.700 10 10 10 63.4 10 24 470
450
9 1.23 4.7 4.7 10 63.4 10 47 150
450
10 0.700 10 10 10 71.5 10 33 330
425
10 1.23 4.7 4.7 10 71.5 10 51 220
425
12 0.700 10 10 10 88.7 10 33 330
350
12 1.23 4.7 4.7 10 88.7 10 75 150 350
REF
COMP
FB
C2
C
C
R
C
ERROR AMP
1
2
04472-004
g
m
Figure 26. Compensation Components
The capacitor (C2) is chosen to cancel the zero introduced by
output capacitance ESR. C2 is calculated using the following
equation:
COMP
OUT
R
CESR
C2
×
=
(19)
For low ESR output capacitance such as with a ceramic capaci-
tor, C2 is optional. For optimal transient performance, the
R
COMP
and C
COMP
may need to be adjusted by observing the load
transient response of the ADP1610. For most applications, the
compensation resistor is to be in the range of 30 kΩ to 400 kΩ,
and the compensation capacitor is to be in the range of 100 pF
to 1.2 nF. Table 5 shows external component values for several
applications.
SOFT START CAPACITOR
The voltage at SS ramps up slowly by charging the soft start
capacitor (C
SS
) with an internal 3 µA current source. Table 6
listed the values for the soft start period, based on maximum
output current and maximum switching frequency.
The soft start capacitor limits the rate of voltage rise on the COMP
pin. This limits the peak switch current at startup. Table 6 shows a
typical soft start period (t
SS
) at maximum output current (I
OUT_MAX
)
for several conditions.
A 20 nF soft start capacitor results in negligible input current
overshoot at startup and is therefore suitable for most applications.
However, if an unusually large output capacitor is used, a longer
soft start period is required to prevent input inrush current.
Table 6. Typical Soft Start Period
V
IN
(V) V
OUT
(V) C
OUT
(μF) C
SS
(nF) t
SS
(ms)
3.3 5 10 20 0.3
5 10 100 2
9 10 20
2.5
9 10 100
8.2
12 10 20
3.5
12 10 100
15
5 9 10 20
0.4
9 10 100
1.5
12 10 20
0.62
12 10 100 2
Conversely, if fast startup is a requirement, the soft start capacitor
can be reduced or even removed, allowing the ADP1610 to start
quickly, but allowing greater peak switch current (see Figure 22
to Figure 25).