AMC3100
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):
R1
R2
⎛
⎝
⎞
⎟
0.6V≦VOUT≦5.5V
(1)
VOUT = 0.6V 1+
⎜
⎠
The external resistor divider sets the output voltage (see figure 1). Choose R1 around 1MΩ, R2 is then given by:
R1
R 2 =
V
⎛
⎜
⎞
⎟
OUT
− 1
0.6V
⎝
⎠
VOUT＝2.5V
Table 1- Resistor Selection vs. Adjust Output Voltage.
L1
C1
22pF
R1
2.2uH
VIN＝2.5V to 5.5V
Rectified
VOUT
1.2V
1.5V
1.8V
2.5V
R1
R2
1MΩ
VIN
SW
1MΩ, 1%
1MΩ, 1%
1MΩ, 1%
1MΩ, 1%
1MΩ, 1%
667KΩ, 1%
500KΩ, 1%
316KΩ, 1%
FB
R2
316KΩ
AMC3100-ADJ
COUT
10uF
CIN
4.7uF
RUN
GND
3.3V
1MΩ, 1%
222KΩ, 1%
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.
Higher VIN or VOUT also increases the ripple current as shown in the formula (2):
⎛
⎞
VOUT
fL
VOUT
VIN
Where, f = operating frequency, andΔIL = ripple current in the inductor.
(2)
⎜
⎜
⎟
⎟
∆IL =
1−
⎝
⎠
COUT selection:
The output capacitor keeps output voltage ripple small and ensures regulation loop stable. The output capacitor
impedance shall be low in switching frequency. The output rippleΔVOUT approximately:
⎛
⎞
1
Where, COUT = output capacitance.
⎜
⎟
⎟
∆VOUT ≅ ∆IL ESR +
⎜
⎝
8 fCOUT
⎠
Copyright © 2006 ADDtek Corp.
8
DD010_A -- JUNE 2006
ADDTEK [ ADDTEK CORP ]
