amc3100 ADDtek Corp, amc3100 Datasheet - Page 8

• Manufacturer Part Number: amc3100
• Description: 1.5mhz, 600ma Synchronous Step-down Converter
• Manufacturer: ADDtek Corp

requirement:
Adjustable Output Voltage:
Inductor selection:
based on the desired ripple current. Large value inductors lower ripple current, and small value inductors result in
higher ripple currents.
C
impedance shall be low in switching frequency. The output rippleΔV
Copyright © 2006 ADDtek Corp.
V
Rectified
∆
IN
V
OUT
＝2.5V to 5.5V
OUT
4.7uF
C
The output capacitor keeps output voltage ripple small and ensures regulation loop stable. The output capacitor
selection:
IN
≅
The basic AMC3100 application circuit is shown in Figure 1. External component selection is driven by load
In adjustable version, the output voltage is set by the below formula (1):
The external resistor divider sets the output voltage (see figure 1). Choose R1 around 1MΩ, R2 is then given by:
For most applications, the value of the inductor will fall in the range of 1uH to 4.7uH. Its value is chosen
Higher V
∆
I
L
⎛
⎜ ⎜
⎝
ESR
V
∆
R
I
OUT
2
IN
L
+
VIN
RUN
=
=
or V
8
V
=
AMC3100-ADJ
fC
⎛
⎜
⎝
OUT
fL
1
V
0
0
OUT
Figure 1
OUT
6 .
6 .
OUT
⎛
⎜ ⎜
⎝
SW
V
R
V
1
⎞
⎟ ⎟
⎠
−
1
also increases the ripple current as shown in the formula (2):
GND
⎛
⎜
⎝
1
−
V
V
OUT
Where, C
+
1
L1
2.2uH
IN
⎞
⎟
⎠
R
R
⎞
⎟ ⎟
⎠
1
2
⎞
⎟
⎠
FB
Where, f = operating frequency, and
OUT
316KΩ
1MΩ
R2
R1
0.6V≦V
APPLICATION INFORMATION
= output capacitance.
22pF
C1
C
10uF
OUT
OUT
V
OUT
≦5.5V
＝2.5V
8
Table 1- Resistor Selection vs. Adjust Output Voltage.
OUT
Δ
approximately:
V
1.2V
1.5V
1.8V
2.5V
3.3V
OUT
I
L
= ripple current in the inductor.
1M Ω , 1%
1M Ω , 1%
1M Ω , 1%
1M Ω , 1%
1M Ω , 1%
R1
DD010_A -- JUNE 2006
AMC3100
667K Ω , 1%
500K Ω , 1%
316K Ω , 1%
222K Ω , 1%
1M Ω , 1%
R2
(1)
(2)