MAX1996AETI+ Maxim Integrated Products, MAX1996AETI+ Datasheet - Page 17

• Manufacturer Part Number: MAX1996AETI+
• Description: Display Drivers CCFL Backlight Controller
• Manufacturer: Maxim Integrated Products

Specifications of MAX1996AETI+

• Lead Free Status / Rohs Status: Details

Figure 10. DPWM Synchronization
The MAX1996A includes POR and UVLO circuits. The
POR resets all internal registers such as DAC output,
fault conditions, and all SMBus registers. POR occurs
when V
olds are only guaranteed to meet electrical characteris-
tic limits for V
continues to function down to the POR threshold.
The UVLO is activated and disables both high-side and
low-side switch drivers when V
When the MAX1996A is placed in shutdown, all func-
tions of the IC are turned off except for the 5.3V linear
regulator that powers all internal registers and the
SMBus interface. The SMBus interface is accessible in
shutdown. In shutdown, the linear regulator output volt-
age drops to about 4.5V and the supply current is 6µA
(typ), which is the required power to maintain all inter-
nal register states. While in shutdown, lamp-out detec-
tion and short-circuit detection latches are reset. The
device can be placed into shutdown by either writing to
the shutdown mode register (SMBus mode only) or with
SH/SUS.
For safety, the MAX1996A monitors the lamp current to
detect the open-lamp fault. When the peak voltage on
IFB drops below 150mV (IFB regulation point must be
set above 48mV) the lamp-out timer starts. Before the
timer times out, V
an attempt to maintain lamp-current regulation. As V
rises, V
reaches its preset limit. At this point, V
limits the secondary voltage by limiting t
V
trol loop is able to quickly limit the secondary voltage.
CCV
SYNCHRONIZATION
is limited to 150mV above V
CC
SIGNAL
CCV
DPWM
is below 1.5V. The SMBus input-logic thresh-
SMBus
rises with it until the secondary voltage
CC
CCI
______________________________________________________________________________________
as low as 3.5V, but the interface
increases the secondary voltage in
ADC-
ADC+
500pF
10kΩ
Low-Power Shutdown
Lamp-Out Detection
CC
is below 4.2V (typ).
Range, CCFL Backlight Controller
CCI
POR and UVLO
High-Efficiency, Wide Brightness
VL
REF
MODE
, the voltage con-
GND
CCV
ON
MAX1996A
. Because
stops and
CCI
Without this clamping feature, the transformer voltage
would overshoot to dangerous levels because V
would take more time to slew down from its supply rail. If
the peak voltage on IFB does not rise above 150mV
before timeout, the MAX1996A shuts down the full
bridge.
The MAX1996A senses overcurrent faults on each
switching cycle. The current comparator monitors the
voltage drop from LX_ to GND. If the voltage exceeds
the current-limit threshold, the regulator turns off the
high-side switch to prevent the transformer primary cur-
rent from increasing further.
The MAX1996A’s standard application circuit, shown in
Figure 1, regulates the current of a 4.5W CCFL. The
IC’s analog voltage interface sets the lamp brightness
with a greater than 30 to 1 power adjustment range.
This circuit operates from a wide supply voltage range
of 4.6V to 28V. Typical applications for this circuit
include notebook, desktop monitor, and car navigation
displays. Table 4 shows the recommended compo-
nents for the power stage of the 4.5W application. To
select the correct component values, several C
parameters (Table 6) and the DC input characteristics
must be specified.
The MAX1996A requires four external switches—NL1,
NL2, NH1, and NH2—to form a full bridge to drive CCFL.
The regulator senses drain-to-source voltage of NL1 and
NL2 to detect the transformer primary minimum current
crossing and overcurrent fault condition. R
and NL2 should be matched. Select a dual logic-level N-
Figure 11. Simple RC Oscillator
REF
100kΩ
1%
Applications Information
Overcurrent Fault Detection
C
100kΩ
1%
R
MAX9031
V
CC
and Protection
TO MODE
DSON
MOSFETs
of NL1
CCV
CFL
17