AMC3100

Copyright

© 2006 ADDtek Corp.

8

DD010_A -- JUNE 2006

APPLICATION INFORMATION

The basic AMC3100 application circuit is shown in Figure 1. External component selection is driven by load

requirement:

Adjustable Output Voltage:

In adjustable version, the output voltage is set by the below formula (1):

⎟

⎠

⎞

⎜

⎝

⎛ +

=

2

1

1

6

.

0

R

R

V

V

OUT

(1)

The external resistor divider sets the output voltage (see figure 1). Choose R1 around 1MΩ, R2 is then given by:

⎟

⎠

⎞

⎜

⎝

⎛

−

=

1

6

.

0

1

2

V

V

R

R

OUT

AMC3100-ADJ

RUN

SW

GND

L1

2.2uH

Rectified

VIN

FB

4.7uF

10uF

R1

1MΩ

R2

316KΩ

C1

22pF

Figure 1

Inductor selection:

For most applications, the value of the inductor will fall in the range of 1uH to 4.7uH. Its value is chosen

based on the desired ripple current. Large value inductors lower ripple current, and small value inductors result in

higher ripple currents.

⎟⎟

⎠

⎞

⎜⎜

⎝

⎛

−

=

∆

IN

OUT

OUT

L

V

V

fL

V

I

1

Where, f = operating frequency, andΔI

(2)

The output capacitor keeps output voltage ripple small and ensures regulation loop stable. The output capacitor

⎟⎟

⎠

⎞

⎜⎜

⎝

⎛

+

∆

≅

∆

OUT

L

OUT

fC

ESR

I

V

8

1

Table 1- Resistor Selection vs. Adjust Output Voltage.

R1

R2

1.2V

1.5V

1.8V

2.5V

3.3V