Rainbow-electronics MAX749 Manual do Utilizador descarregar pdf (Página 9)

Figure 9b. Maximum Output Current vs. Input Voltage,

OUT

= -12V

Figure 9c. Maximum Output Current vs. Input Voltage,

OUT

= -15V

Figure 9d. Maximum Output Current vs. Input Voltage,

OUT

= -24V

Figure 9e. Maximum Output Current vs. Input Voltage,

OUT

= -48V

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.

MAX749

Digitally Adjustable LCD Bias Supply

_______________________________________________________________________________________ 9

Figure 9a. Maximum Output Current vs. Input Voltage,

OUT

= -5V

MAX749-Fig 13

INPUT VOLTAGE (V)

MAXIMUM OUTPUT CURRENT (mA)

SENSE

(Ω)

3245

1.0

0.5

0.3

0.25

0.2

OUT

= -48V

L = 47µH

MAX-749-Fig10

INPUT VOLTAGE (V)

MAXIMUM OUTPUT CURRENT (mA)

100

120

140

OUT

= -12V

L = 47µH

SENSE

(Ω)

0.2

0.25

0.3

0.5

1.0

MAX749-Fig 11

INPUT VOLTAGE (V)

MAXIMUM OUTPUT CURRENT (mA)

100

SENSE

(Ω)

OUT

= -15V

L = 47µH

0.2

0.25

0.3

0.5

1.0

MAX749-Fig 12

INPUT VOLTAGE (V)

MAXIMUM OUTPUT CURRENT (mA)

SENSE

(Ω)

1.0

0.5

0.3

0.25

0.2

OUT

= -24V

L = 47µH

MAX749-Fig 9

INPUT VOLTAGE (V)

MAXIMUM OUTPUT CURRENT (mA)

SENSE

(Ω)

100

150

200

250

3245

1.0

0.5

0.3

0.25

0.2

OUT

= -5V

L = 47µH

1 2 3 4 5 6 7 8 9 10 11 12

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