DS3994Z+W Maxim Integrated Products, DS3994Z+W Datasheet - Page 9

• Manufacturer Part Number: DS3994Z+W
• Description: Display Drivers 4-Ch Cold-Cathode Fl uorescent Controller
• Manufacturer: Maxim Integrated Products

Specifications of DS3994Z+W

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

Figure 1. Per Channel Logic Diagram
The DS3994 uses a push-pull drive scheme to convert
a DC voltage (5V to 24V) to the high-voltage (600V
to 1200V
the CCFLs. The push-pull drive scheme uses a minimal
number of external components, which reduces
assembly cost and makes the printed circuit board
design easy to implement. The push-pull drive scheme
also provides an efficient DC-to-AC conversion and
produces near-sinusoidal waveforms.
Each DS3994 channel drives two logic-level n-channel
MOSFETs that are connected between the ends of a
step-up transformer and ground (see Figure 1 and the
Typical Operating Circuit ). The transformer has a center
tap on the primary side that is connected to a DC voltage
supply. The DS3994 alternately turns on the two
MOSFETs to create the high-voltage AC waveform on the
secondary side. By varying the duration of the MOSFET
turn-on times, the controller is able to accurately control
the amount of current flowing through the CCFL.
A resistor in series with the CCFL’s ground connection
enables current monitoring. The voltage across this
resistor is fed to the lamp current monitor (LCM) input
on the DS3994. The DS3994 compares the peak resistor
voltage against an internal reference voltage to deter-
mine the duty cycle for the MOSFET gates. Each CCFL
512 x LAMP FREQUENCY
[10.24MHz ~ 40.96MHz]
DIMMING PWM SIGNAL
LAMP FREQUENCY
CHANNEL ENABLE
CHANNEL FAULT
[20kHz ~ 80kHz]
RMS
) AC waveform that is required to power
Detailed Description
CONTROLLER
DIGITAL
CCFL
_____________________________________________________________________
Fluorescent Lamp Controller
64 LAMP CYCLE
INTEGRATOR
RMS
LAMP MAXIMUM VOLTAGE REGULATION
LAMP STRIKE AND REGULATION
4-Channel Cold-Cathode
receives independent current monitoring and control,
which results in equal brightness across all of the lamps
and maximizes the lamp’s brightness and lifetime.
The DS3994 can also drive more than one lamp per
channel. See the Typical Operating Circuit section for
implementation details when using multiple lamps per
channel.
The DS3994 uses an I
communication with the on-board EEPROM configuration
registers and user memory. The configuration registers,
four Burst Dimming Stagger Registers (BDS1/2/3/4), and
three Control Registers (CR1/2/3)—allow the user to cus-
tomize many DS3994 parameters such as the time delay
to stagger the burst dimming between channels, the
lamp and dimming frequency sources, fault-monitoring
options, and channel enabling/disabling. The three bytes
of nonvolatile user memory can be used to store manu-
facturing data such as date codes, serial numbers, or
product identification numbers.
The device is shipped from the factory with the con-
figuration registers programmed to a set of default
configuration parameters. To inquire about custom
factory programming, please send an email to
[e-mail].
LOC BIT IN CR1.0
OVERVOLTAGE
LAMP OVERCURRENT
EEPROM Registers and I
LAMP OUT
2
C-compatible serial interface for
1.0V
400mV
2.0V
1.0V
DRIVERS
GATE
OVDn
OVERVOLTAGE DETECTOR
Serial Interface
2
C-Compatible
LCMn
LAMP CURRENT
MONITOR
GAn
GBn
MOSFET
DRIVERS
GATE
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