ML4871CS-3 MICRO-LINEAR [Micro Linear Corporation], ML4871CS-3 Datasheet - Page 8

• Manufacturer Part Number: ML4871CS-3
• Description: High Current Boost Regulator
• Manufacturer: MICRO-LINEAR [Micro Linear Corporation]

ML4871
DESIGN EXAMPLE
In order to design a boost converter using the ML4871, it
is necessary to define a few parameters. For this example,
assume that V
I
First, it must be determined whether the ML4871 is
capable of delivering the output current. This is done using
Equation 1:
Next, select an inductor. As previously mentioned, the
recommended inductance is 10µH. Make sure that the
peak current rating of the inductor is at least 1.5A, and
that the DC resistance of the inductor is in the range of 50
to 100m .
Finally, the value of the output capacitor is determined
using Equation 2:
The closest standard value would be a 100µF capacitor
with an ESR rating of 100m . If such a low ESR value
cannot be found, two 47µF capacitors in parallel could
also be used.
8
OUT(MAX)
I
C
OUT MAX
OUT
V
IN
1.8
2.0
2.2
2.4
2.6
2.8
3.0
3.2
3.4
3.6
3.8
4.0
4.2
4.4
4.6
4.8
(
(V)
= 500mA.
=
)
44 10
IN
=
5 0
125
™
.
= 3.0V to 3.6V, V
.
V
™
m
H
30
50
V
=
.
.
OUT
88
V
V
386.2
451.9
521.5
585.9
651.0
716.5
782.0
m
™
F
= 3.3V
0 7
.
I
OUT(MAX)
OUT
A
=
0 53
= 5.0V, and
.
Table 1. Typical I
A
(mA)
V
OUT
286.2
332.1
379.1
430.0
479.0
525.4
571.8
618.5
665.0
711.7
758.7
805.3
851.9
899.0
946.1
992.7
= 5.0V
OUT
and Efficiency vs. V
The complete circuit is shown in Figure 9. As mentioned
previously, the use of an input supply bypass capacitor is
highly recommended.
V
V
IN
IN
V IN
100µF
= 2.4V, V
= 2.4V, V
I
OUT
1.0
2.0
5.0
10.0
20.0
50.0
100.0
200.0
586.0
1.0
2.0
5.0
10.0
20.0
50.0
100.0
200.0
485.0
Figure 9. Typical Application Circuit
(mA)
OUT
OUT
IN
= 3.3V
= 5.0V
V L1
V IN
GND
DETECT
(Sumida CD75)
ML4871
10µH
PWR GND
EFFICIENCY PERCENTAGE
V OUT
RESET
V L2
82.0
84.4
87.0
87.6
87.9
88.3
88.6
88.2
65.1
84.4
87.0
87.7
88.4
88.9
89.1
88.9
87.5
71.6
100µF
V OUT