ML4851
DESIGN CONSIDERATIONS
R
A
=
R
B
×
LAYOUT
Good PC board layout practices will ensure the proper
operation of the ML4851. Important layout considerations
include:
V
0.2
IN( MIN)
−
1
(Continued)
(6)
TOP LAYER
BOTTOM LAYER
n
Use adequate ground and power traces or planes
n
Keep components as close as possible to the ML4851
n
Use short trace lengths from the inductor to the V
L
pin
and from the output capacitor to the V
OUT
pin
n
Use a single point ground for the ML4851 PWR GND
pin and the input and output capacitors, and connect
GND to PWR GND with a separate trace
A sample PC board layout is shown in Figure 6.
Figure 6. Sample PC Board Layout
ML4851-3
V
IN
L = 10µH
1.0
1.5
2.0
L = 18µH
1.0
1.5
2.0
2.5
3.0
L = 33µH
1.0
1.5
2.0
2.5
3.0
L = 56µH
1.0
1.5
2.0
2.5
3.0
I
OUT
(mA)
45.8
108.3
184.1
30.1
70.9
125.5
185.7
243.4
17.6
42.7
76.1
120.4
159.6
10.6
25.9
47.6
75.8
108.0
EFFICIENCY PERCENTAGE
77.6
77.7
77.9
82.5
83.5
83.9
84.5
85.4
86.0
87.8
88.7
89.7
90.7
85.2
89.1
90.8
92.0
93.1
ML4851-5
V
IN
L = 10µH
1.0
1.5
2.0
L = 18µH
1.0
1.5
2.0
2.5
3.0
3.5
L = 33µH
1.0
1.5
2.0
2.5
3.0
3.5
4.0
4.5
L = 56µH
1.0
1.5
2.0
2.5
3.0
3.5
4.0
4.5
I
OUT
(mA)
24.2
68.0
123.1
15.7
43.3
80.4
125.3
169.9
236.9
9.1
24.8
47.4
74.5
106.9
147.5
190.0
227.8
5.5
13.9
28.5
45.7
67.1
92.5
122.1
149.6
EFFICIENCY PERCENTAGE
78.3
79.9
80.3
82.3
84.8
85.7
86.2
86.5
87.0
83.5
87.0
88.6
89.5
90.3
90.8
91.4
92.1
80.1
85.9
88.9
90.3
91.4
92.3
92.6
93.8
Table 1. Maximum Output Current and Efficiency vs. V
IN
8
July, 2000
DATASHEET
MICRO-LINEAR [ MICRO LINEAR CORPORATION ]
