ADP2105/ADP2106/ADP2107

Rev. 0 | Page 15 of 32

APPLICATIONS INFORMATION

EXTERNAL COMPONENT SELECTION

The external component selection for the ADP2105/ADP2106/

ADP2107 application circuits shown in Figure 35 and Figure 36

depend on input voltage, output voltage, and load current

requirements. Additionally, tradeoffs between performance

parameters like efficiency and transient response can be made

by varying the choice of external components.

SETTING THE OUTPUT VOLTAGE

The output voltage of ADP2105/ADP2106/ADP2107-ADJ is

externally set by a resistive voltage divider from the output

voltage to FB. The ratio of the resistive voltage divider sets the

output voltage, while the absolute value of those resistors sets

the divider string current. For lower divider string currents, the

small 10 nA (0.1 μA maximum) FB bias current should be taken

into account when calculating resistor values. The FB bias

current can be ignored for a higher divider string current, but

this degrades efficiency at very light loads.

To limit output voltage accuracy degradation due to FB bias

current to less than 0.05% (0.5% maximum), ensure that the

divider string current is greater than 20 μA. To calculate the

desired resistor values, first determine the value of the bottom

STRING

FB

BOT

I

V

R

=

where:

OFF

EN

SS

LX2

AGND

OUTPUT VOLTAGE = 1.2V, 1.5V, 1.8V, 3.3V

COMP

ON

PGND

GND

GND

GND

NC

LX1

PWIN2

1

2

3

4

12

11

10

9

16

15

14

13

5

6

7

8

L

LOAD

10Ω

0.1μF

NC = NO CONNECT

ADP2105/

ADP2106/

ADP2107

OUT_SENSE

PWIN1

IN

GND

Figure 35. Typical Applications Circuit for Fixed Output Voltage Options (ADP2105/ADP2106/ADP2107-xx)

OFF

EN

SS

LX2

FB

PWIN1

AGND

OUTPUT VOLTAGE

COMP

ON

PGND

IN

GND

GND

GND

NC

GND

LX1

PWIN2

FB

1

2

3

4

12

11

10

9

16

15

14

13

5

6

7

8

L

LOAD

10Ω

0.1μF

FB

NC = NO CONNECT

ADP2105/

ADP2106/

ADP2107

Figure 36. Typical Applications Circuit for Adjustable Output Voltage Option (ADP2105/ADP2106/ADP2107-ADJ)