Data Sheet

ADP1607

Rev. C | Page 13 of 16

CHOOSING THE INPUT CAPACITOR

The ADP1607 requires a 10 µF or greater input bypass capacitor

maintaining a constant input voltage. The value of the input

capacitor can be increased without any limit for smaller input

voltage ripple and better input voltage filtering. The capacitor must

have a 4 V or higher voltage rating to support the maximum

close to the ADP1607 as possible.

Different types of capacitors can be considered, but for battery-

powered applications, the best choice is the multilayer ceramic

capacitor, due to its small size, low equivalent series resistance

(ESR), and low equivalent series inductance (ESL). X5R or X7R

dielectrics are recommended. Y5V capacitors should not be used

due to their variation in capacitance over temperature. Alterna-

tively, use a high value, medium ESR capacitor in parallel with a

0.1 µF low ESR capacitor.

CHOOSING THE OUTPUT CAPACITOR

maintain the output voltage and supply current to the load. The

output capacitor supplies the current to the load when the N-

When choosing the output capacitor, it is also important to account

for the loss of capacitance due to output voltage dc bias. This

may result in using a capacitor with a higher rated voltage to

achieve the desired capacitance value. See Figure 25 for an

example of how the capacitance of a 10 µF ceramic capacitor

changes with the dc bias voltage.

0

2

4

6

8

10

12

0

1

2

3

4

5

6

DC BIAS VOLTAGE (V)

Figure 25. Typical Ceramic Capacitor Performance

The value and characteristics of the output capacitor greatly

affect the output voltage ripple, transient performance, and

continuous operation is calculated as follows:

OUT

ON

OUT

OUT

C

OUT

C

t

I

C

Q

V

×

=

=

∆

(4)

where:

SW

ON

f

D

t

=

(5)

and,

OUT

IN

OUT

V

V

V

D

−

=

(6)

As shown in the duty cycle and output ripple voltage equations,

the output voltage ripple increases with the load current.