Rainbow-electronics MAX1543 Manual do Utilizador descarregar pdf (Página 14)

MAX1542/MAX1543

TFT LCD DC-to-DC Converter with

Operational Amplifiers

14 ______________________________________________________________________________________

Thermal-Overload Protection

Thermal-overload protection prevents excessive power

dissipation from overheating the MAX1542/MAX1543.

When the junction temperature exceeds T

= +160°C, a

thermal sensor immediately activates the fault protec-

tion, which shuts down the device, allowing the IC to

cool. The input voltage must fall (below V

UVLO

) to clear

the fault latch and reactivate the controller.

Thermal-overload protection protects the controller in

the event of fault conditions. For continuous operation,

do not exceed the absolute maximum junction-temper-

ature rating of T

= +150°C.

Applications Information

Inductor Selection

The primary considerations in inductor selection are

inductor physical shape, circuit efficiency, and cost.

The factors that determine the inductance value are

input voltage, output voltage, switching frequency, and

maximum output current. Final inductor selection

includes ensuring the chosen inductor meets the appli-

cation’s peak current and RMS current requirements.

Very high inductance values minimize the current ripple

and therefore reduce the peak current, which decreas-

es core losses in the inductor and I

R losses in the cir-

cuit’s entire power path. However, large inductance

PGND

FREQ*

COMP

5µA

ERROR

COMPARATOR

ERROR

AMPLIFIER

CLOCK

MAX1542

MAX1543

CURRENT

SENSE

CONTROL

AND DRIVER

LOGIC

SOFT-

START

SLOPE

COMPEN-

SATION

OSCILLATOR

1.24V

∑

AGND

SWITCH

CONTROL

(SEE FIGURE 4)

OUT2

NEG2

POS2

OUT1

NEG1

POS1

DEL CTLSRC COM DRN*

SUP

EXT*

*MAX1543 ONLY.

5µA

Figure 3. Functional Diagram

1 2 ... 9 10 11 12 13 14 15 16 17 18 19 20

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