Rainbow-electronics MAX754 Bedienungsanleitung PDF herunterladen (Seite 15)

MAX753/MAX754

CCFL Backlight and

LCD Contrast Controllers

______________________________________________________________________________________ 15

MAX753

6-BIT DAC

PULSE-SKIP

COMPARATOR

PRESET

6-BIT COUNTER

CLK

DAC

LFB

REF

LDRV

BATT

+5V INPUT

LON

GND

PGND

LADJ

C1

0.22µF

L2

33µH

BATTERY

INPUT

D8

1N5819

NEGATIVE

LCD-BIAS

OUTPUT

ON/OFF

CONTROL

ON-TIME

LOGIC

OFF-TIME

LOGIC

C2

10µF

C15

1µF

R19

2.2Ω

C6

10µF

35V

ALTERNATE

D8 CONNECTION

(SEE TEXT)

C4

0.22µF

D3

1N5819

Figure 8. MAX753 Negative LCD-Bias Generator

* DAC OUTPUT VOLTAGE = REF - LFB

625

635

645

DAC CODE

ZERO SCALE

DAC OUTPUT VOLTAGE (mV)*

MID SCALE FULL SCALE

30 31 32 61 62 63

918

928

937

1220

1230

1240

Figure 9. MAX753 LCD DAC Transfer Function

The MAX753’s DAC transfer function is shown in Figure 9.

The following equation relates the switching regulator’s

regulated output voltage to the DAC’s voltage (REF - LFB):

The value REF - LFB (and not LFB) is specified in the

Electrical Characteristics

. The most negative output

voltage occurs for the largest value of REF - LFB.

The MAX753’s combination boost converter and

charge-pump inverter was chosen over a conventional

buck-boost inverter because it allows the use of low-

cost N-channel MOSFETs instead of more expensive P-

channel ones. Additionally, its efficiency is 5% to 10%

better than a standard buck-boost inverter.

V REF 1

REF LFB

OUT

=−+













−

()

1 2 ... 10 11 12 13 14 15 16

Kommentare zu diesen Handbüchern

Keine Kommentare

Rainbow-electronics MAX754 Bedienungsanleitung Seite 15

Kommentare zu diesen Handbüchern

Verwandte Produkte und Handbücher für Sensoren Rainbow-electronics MAX754