MAX1739EEP+ Maxim Integrated Products, MAX1739EEP+ Datasheet - Page 18

• Manufacturer Part Number: MAX1739EEP+
• Description: Display Drivers Wide Brightness Rang e CCFL Backlight Con
• Manufacturer: Maxim Integrated Products

Specifications of MAX1739EEP+

• Lead Free Status / RoHS Status: Lead free / RoHS Compliant

Wide Brightness Range
CCFL Backlight Controllers
a proven application that is useful for a wide range of
CCFL tubes and power ranges. Table 5 shows the rec-
ommended components for a 4.5W application.
The MAX1739/MAX1839 require three external switches
to operate: N1, N2A, and N2B. N1 is the buck switch;
select a logic-level N-channel MOSFET with low R
to minimize conduction losses (100mΩ, 30V typ). Also
select a comparable-power Schottky diode for D1.
N2A/N2B are the Royer oscillator switches that drive
the transformer primary; select a dual-logic-level N-
channel MOSFET with low R
tion losses (100mΩ, 30V typ).
Table 4. CCFL Specifications
18
Table 5. Components for the Standard Application Circuit
DESIGNATION
CCFL Minimum Strike
Voltage
(Kick-Off Voltage)
CCFL Typical Operating
Voltage
(Lamp Voltage)
CCFL Maximum Operating
Current (Lamp Current)
CCFL Maximum Frequency
(Lamp Frequency)
______________________________________________________________________________________
SPECIFICATION
L1
N1
N2
T1
D1
D2
D3
C6
C7
47µH, 1.1A inductor
30V, 0.1Ω N-channel MOSFET
30V, 95mΩ dual N-channel MOSFET
8.7µH, 180:1 transformer
30V, 1A Schottky diode
0.1A Schottky diode
0.1A dual Schottky diode
22pF, 3.1kV capacitor
0.1µF, 63V, low-dissipation capacitor
DSON
SYMBOL
DESCRIPTION
V L
V
I L
f L
S
to minimize conduc-
MOSFETs
mA
UNITS
V
V
kHz
RMS
RMS
RMS
DSON
Although CCFLs typically operate at <550V RMS , a higher voltage
(1000V
voltage is typically higher at cold temperatures and at the tube’s end
of life. This voltage is set by the combination of the maximum primary
voltage (center-tap voltage limit corresponding to
V
Once a CCFL has been struck, the voltage required to maintain light
output falls to approximately 550V
little as 250V
constant, even as the tube’s brightness is varied.
The maximum RMS AC current through a CCFL is typically 5mA
DC current is not allowed through CCFLs. The maximum lamp current
is set by the sense resistor (R13) at the maximum brightness setting.
The maximum AC-lamp-current frequency. The MAX1739/ MAX1839
synchronize to the Royer oscillator frequency set by the external
components and are designed to operate between 32kHz and
100kHz.
CTFB
= 0.6V) and the transformer (T1) turns ratio.
RMS
R4 and R5 sense the transformer’s primary voltage.
Figure 9 shows the relationship between the primary
and secondary voltage. To set the maximum average
secondary transformer voltage, set R5 = 10kΩ, and
select R5 according to the following formula:
where V
voltage (above the strike voltage), and N is the turns
ratio of the transformer.
CR104-470
FDN361AN
FDC6561AN
5371-T001 (CIUH842 style)
CRS02
BAT54
MMBD4148SE
GHM1038-SL-220J-3K
SMD1812
and up) is required initially to start the tube. The strike
RECOMMENDED DEVICE
RMS
. The CCFL operating voltage stays relatively
S
is the maximum RMS secondary transformer
R
4
DESCRIPTION
=
R
5
RMS
⎛
⎜
⎝
1 5
.
. Short tubes may operate on as
V
S RMS
N
(
Sense Resistors
)
MANUFACTURER
−
1
⎞
⎟
⎠
Fairchild
Fairchild
Fairchild
Fairchild
Toshiba
Sumida
Sumida
Murata
WIMA
RMS
.