DS3992Z-18P+ Maxim Integrated Products, DS3992Z-18P+ Datasheet - Page 9

• Manufacturer Part Number: DS3992Z-18P+
• Description: IC CTRLR CCFL 180-440HZ 16-SOIC
• Manufacturer: Maxim Integrated Products
• Type: CCFL Controllerr

Specifications of DS3992Z-18P+

• Frequency: 40 ~ 80 kHz
• Current - Supply: 8mA
• Voltage - Supply: 4.5 V ~ 5.5 V
• Operating Temperature: -40°C ~ 85°C
• Package / Case: 16-SOIC (3.9mm Width)
• Lead Free Status / RoHS Status: Lead free / RoHS Compliant
• Current - Output: -
• Lead Free Status / Rohs Status: Details

Figure 4. Fault-Handling Flowchart
When both the DS3992 and the DC inverter supplies
are at acceptable levels, the DS3992 will attempt to
strike the lamps. The DS3992 slowly ramps up the
MOSFET gate duty cycle until the lamp strikes. The
controller detects that the lamp has struck by detecting
current flow in the lamp. If during the strike ramp, the
maximum allowable voltage is reached, the controller
will stop increasing the MOSFET gate duty cycle to
keep from overstressing the system. The DS3992 will
go into a fault-handling state if the lamp has not struck
after 65,536 lamp cycles. If an overvoltage event is
detected during the strike attempt, the DS3992 will dis-
able the MOSFET gate drivers and go into the fault-
handling state.
Once the lamp is struck, the DS3992 moves to the run
lamp stage. In the run lamp stage, the DS3992 adjusts
the MOSFET gate duty cycle to optimize the lamp cur-
rent. The gate duty cycle is always constrained to keep
the system from exceeding the maximum allowable
lamp voltage. If lamp current ever drops below the
lamp out reference point for 65536 lamp cycles, then
the lamp is considered extinguished. In this case the
MOSFET gate drivers are disabled and the device
moves to the fault handling stage.
LAMP OVERCURRENT
[INSTANTANEOUS]
Two-Channel, Push-Pull CCFL Controller
[RAMP AND REGULATE TO
CURRENT BOUNDED BY
_____________________________________________________________________
INVERTER SUPPLIES
AT PROPER LEVELS?
IF LINE REGULATION
THRESHOLD IS MET
OVD THRESHOLD]
[REGULATE LAMP
LAMP VOLTAGE]
STRIKE LAMP
DEVICE AND
RUN LAMP
YES
MOSFET GATE DRIVERS ENABLED
RUN LAMP STAGE
LAMP STRIKE TIMEOUT
[65536 LAMP CYCLES]
[65,536 LAMP CYCLES]
In the case of a lamp overcurrent condition, the
DS3992 will instantaneously declare the controller to be
in a fault state. If either channel on the DS3992 goes
into the fault state, only the faulty channel will be shut
down. Once a fault state is entered, the controller will
remain in that state until one of the following occurs:
•
•
External component selection has a large impact on the
overall system performance and cost. The two most
important external components are the transformers
and n-channel MOSFETs.
The transformer should be able to operate in the 40kHz
to 80kHz frequency range of the DS3992, and the turns
ratio should be selected so the MOSFET drivers run at
28% to 35% duty cycle during steady-state operation.
The transformer must be able to withstand the high
open-circuit voltage that will be used to strike the lamp.
Additionally, its primary/secondary resistance and
inductance characteristics must be considered
because they contribute significantly to determining the
[64 LAMP CYCLES]
LAMP-OUT TIMEOUT
OVERVOLTAGE
V
The SVM input drops below 2.0V.
CC
drops below the UVLO threshold.
Applications Information
[MUST POWER CYCLE THE DS3992
OR TAKE SVM BELOW 2V TO RESET
THE CCFL CONTROLLER]
FAULT STATE
Component Selection
9