MAX753CSLASHD datasheet(11/16 Pages) MAXIM

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CCFL Backlight and

LCD Contrast Controllers

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Table 3. Spreadsheet Design Equations

T1 Center-Tap Peak Voltage

PARAMETER

SYMBOL

MIN

TYP

MAX

VTAP,PK

Strike Voltage (VS)

VS,RMS

1100

1500

= -SQRT(2) * ILAMP,RMS(max) /

(CBAL * w * SIN(phi)) / n

Discharging Tube Voltage (VL)

VLAMP,RMS

435

Bias Voltage

VLCD

= VLCD(max) / 2

32.6

Output Current

ILCD

0.0245

T1 Turns Ratio (Sec/Pri)

171

T1 Resonating Inductance

LMAG

0.000045

C9 Value

CRES

2.2E-07

C10 Value

CBAL

1.5E-11

Royer Frequency

= SQRT [1 / (LMAG * CRES)]

Reference Voltage

VREF

1.25

Second Volts Constant

0.000008

2.4E-05

R8 Current-Sensing Resistor

= PI() * VREF * SQRT(2) /

(2 * ILAMP,RMS(max))

Secondary Voltage Phase vs. Tube

Voltage

phi

= ATAN (-ILAMP,RMS(max) /

(CBAL * w * + VLAMP,RMS)

Secondary Limit Voltage

VLIM

= VS,RMS(max) * 0.9

T1 Center-Tap Limit Peak Voltage

= SQRT(2) * VLIM / n

R5/R6

ROTP,RATIO

= VREF / (D25 - 0.6 - VREF)

VIN(min) Full-Load Switching Period

TFL

= sV(min) / VIN(min) + sV(min) /

(VLCD(max) - VIN(min))

L2 Inductance

= L2(max) * 0.8

= sV(min) ^ 2 / (2 * TFL *

VLCD(max) * ILCD(min))

L2 Peak Currrent

= sV(max) / L2(min)

R4/R3

RLCD,RATIO

= VREF / (VLCD(max) - VREF)

Input Voltage

VIN

= (2 / PI()) * VTAP,PK

Discharging Tube Current (IL)

ILAMP,RMS

= 0.28 *

ILAMP,RMS(max)

0.005

CCFL Specifications

LCD Contrast Voltage Specifications

Royer Specifications

MAX754 Specifications

CCFL Circuit Calculations

LCD Circuit Calculations

Application Circuit Operating Range

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