MAX749ESA Maxim Integrated Products, MAX749ESA Datasheet - Page 9

• Manufacturer Part Number: MAX749ESA
• Description: Display Drivers Digitally Adjustable able LCD Bias Supply
• Manufacturer: Maxim Integrated Products

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.
Figure 9b. Maximum Output Current vs. Input Voltage,
V
Figure 9a. Maximum Output Current vs. Input Voltage,
V
OUT
OUT
= -12V
= -5V
250
200
150
100
140
120
100
50
80
60
40
20
0
0
2
2
V
L = 47 H
V
L = 47 H
OUT
OUT
_______________________________________________________________________________________
= -5V
= -12V
3
3
INPUT VOLTAGE (V)
INPUT VOLTAGE (V)
Digitally Adjustable LCD Bias Supply
4
4
Choosing an Inductor
5
5
6
6
0.2
0.25
0.3
0.5
1.0
0.2
0.25
0.3
0.5
1.0
Figure 9c. Maximum Output Current vs. Input Voltage,
V
Figure 9d. Maximum Output Current vs. Input Voltage,
V
Figure 9e. Maximum Output Current vs. Input Voltage,
V
OUT
OUT
OUT
= -15V
= -24V
= -48V
100
60
50
40
30
20
10
25
20
15
10
80
60
40
20
0
5
0
0
2
2
2
V
L = 47 H
V
L = 47 H
OUT
V
L = 47 H
OUT
OUT
= -24V
3
= -48V
3
3
= -15V
INPUT VOLTAGE (V)
INPUT VOLTAGE (V)
INPUT VOLTAGE (V)
4
4
4
5
5
5
6
6
6
0.2
0.25
0.3
0.5
1.0
0.2
0.25
0.3
0.5
1.0
0.2
0.25
0.3
0.5
1.0
9