MAX1739EEP+ Maxim Integrated Products, MAX1739EEP+ Datasheet - Page 17

• 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

increases the circuit’s demand for current but may not
be enough to blow the fuse. With the buck switch short-
ed, the center tap rises above its regulation point,
which causes the CCV amplifier’s output (V
low. To detect this, the MAX1739/MAX1839 check that
V
this condition persists for over 250ms (or 64 DPWM
pulses), the inverter switch commutation is stopped
with either DL1 or DL2 on. With the buck switch short-
ed, this will cause a short circuit with enough current to
blow the fuse. If the buck switch is not shorted, then the
inverter latches off as in a lamp-out condition.
Both buck-switch short and lamp-out detection will
clear the STATUS1 bit in the SMBus interface. STA-
TUS1 does not clear immediately but will clear about 2
seconds after the inverter has been forced off (see
Digital Interface).
Note that once the inverter board fuse has blown,
SMBus communications with the part will cease since
the MAX1739 will then be without power.
Figure 8. Standard Application Circuit
CCV
is below 1V at the end of every DPWM period. If
4.7μF
C9
(5V TO 28V)
V
IN
C1
DIMMING
______________________________________________________________________________________
ON/OFF
C2
C3
VL
BATT
CCV
CCI
REF
MINDAC
MODE
CRF/SDA
CTL/SCL
SH/SUS
MAX1739
MAX1839
SYNC
CSAV
CTFB
GND
BST
DL2
DL1
DHI
CS
VL
LX
CCV
) to go
CCFL Backlight Controllers
D1
N1
C5
D2
Wide Brightness Range
As shown in the standard application circuit (Figure 8),
the MAX1739/MAX1839 regulate the current of a 4.5W
CCFL. The IC’s analog voltage interface sets the lamp
brightness with a minimum 20:1 power adjustment
range. This circuit operates from a wide supply-voltage
range of 7V to 24V. Typical applications include note-
book, desktop monitor, and car navigation displays.
To select the correct component values for the
MAX1739/MAX1839 circuit, several CCFL parameters
(Table 4) and the minimum DC input voltage must be
specified.
Components T1, C6, C7, N2A, and N2B form the Royer
oscillator. A Royer oscillator is a resonant tank circuit
that oscillates at a frequency dependent on C7, the pri-
mary magnetizing inductance of T1 (LP), and the
impedance seen by the T1 secondary. Figure 8 shows
L1
R4
R5
C4
Applications Information
N2A
C6
T1
C7
CCFL Specifications
N2B
Royer Oscillator
R13
D5
17