MAX749ESA Ver la hoja de datos (PDF) - Maxim Integrated
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MAX749ESA Datasheet PDF : 12 Pages
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Digitally Adjustable LCD Bias Supply
Choosing an Inductor
Practical inductor values range from 22µH to 100µH,
and 47µH is normally a good choice. Inductors with a
ferrite core or equivalent are recommended. The induc-
tor’s saturation current rating – the current at which the
core begins to saturate and the inductance falls to 80%
or 90% of its nominal value – should ideally equal the
current limit (see Current-Sense Resistor section).
However, because the current is limited by the
MAX749, the inductor can safely be driven into satura-
tion with only a slight impact on efficiency.
For highest efficiency, use a coil with low resistance,
preferably under 300mΩ. To minimize radiated noise,
use a toroid, pot-core, or shielded inductor.
250
0.2
VOUT = -5V
200
L = 47µH
0.25
0.3
150
100
0.5
50
1.0
0
2
3
4
5
6
INPUT VOLTAGE (V)
Figure 9a. Maximum Output Current vs. Input Voltage,
VOUT = -5V
140
0.2
120
VOUT = -12V
L = 47µH
100
0.25
80
0.3
60
40
0.5
20
1.0
0
2
3
4
5
6
INPUT VOLTAGE (V)
Figure 9b. Maximum Output Current vs. Input Voltage,
VOUT = -12V
100
0.2
VOUT = -15V
L = 47µH
80
0.25
60
0.3
40
0.5
20
1.0
0
2
3
4
5
6
INPUT VOLTAGE (V)
Figure 9c. Maximum Output Current vs. Input Voltage,
VOUT = -15V
60
0.2
50
VOUT = -24V
L = 47µH
40
0.25
30
0.3
20
0.5
10
1.0
0
2
3
4
5
6
INPUT VOLTAGE (V)
Figure 9d. Maximum Output Current vs. Input Voltage,
VOUT = -24V
25
0.2
20
VOUT = -48V
L = 47µH
0.25
0.3
15
10
0.5
5
1.0
0
2
3
4
5
6
INPUT VOLTAGE (V)
Figure 9e. Maximum Output Current vs. Input Voltage,
VOUT = -48V
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