4-Channel Cold-Cathode

Fluorescent Lamp Controller

22

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Table 5. Transformer Specifications

PARAMETER

CONDITIONS

MIN

TYP

MAX

UNITS

Turns Ratio (Secondary/Primary)

(Notes 11, 12, 13)

40

Frequency

40

80

kHz

Output Power

6W

Output Current

58

mA

Primary DCR

Center tap to one end

200

m

Ω

Secondary DCR

500

Ω

Primary Leakage

12

µH

Secondary Leakage

185

mH

Primary Inductance

70

µH

Secondary Inductance

500

mH

Center Tap Voltage

10.8

12

13.2

V

100ms minimum

2000

Secondary Output Voltage

Continuous

1000

Table 6. Resistor and Capacitor Selection Guide

DESIGNATOR

QTY

VALUE

25°C

TOLERANCE

(%)

TEMPERATURE

COEFFICIENT

NOTES

R1

1

10k

Ω

1—

—

R2

1

12.5k

Ω to

105k

Ω

1—

See the Setting the SVM Threshold Voltage section.

R3

1

20k

Ω to

40k

Ω

1

≤153ppm/°C

2% or less total tolerance. See the Lamp Frequency

Configuration section to determine value.

R4

1

18k

Ω to

45k

Ω

1

≤153ppm/°C

2% or less total tolerance. See the Lamp Frequency

Configuration section to determine value.

R5

1

4.7k

Ω

5

Any grade

—

R6

1

4.7k

Ω

5

Any grade

—

R7

1

4.7k

Ω

5

Any grade

—

R8

1/Ch

140

Ω

1—

See the Setting the RMS Lamp Current section.

C1

1/Ch

100nF

10

X7R

Capacitor value will also affect LCM bias voltage during

power-up. A larger capacitor may cause a longer time

C2

1/Ch

10pF

5

±1000ppm/°C

2kV to 4kV breakdown voltage required.

C3

1/Ch

27nF

5

X7R

Capacitor value will also affect LCM bias voltage during

power-up. A larger capacitor may cause a longer time

C4

1/Ch

33µF

20

Any grade

—

C5

2/DS3984

0.1µF

10

X7R

Note 11: Primary should be Bifilar wound with center tap connection.

Note 12: Turns ratio is defined as secondary winding divided by the sum of both primary windings.

Note 13: 40:1 is the nominal turns ratio for driving a 438mm x 2.2mm lamp with a 12V supply. Refer to AN3375 for more information.