DS3988T+T&R Maxim Integrated Products, DS3988T+T&R Datasheet - Page 9

• Manufacturer Part Number: DS3988T+T&R
• Description: Display Drivers 8-Ch CCFL Controller All N-FET Drive, La
• Manufacturer: Maxim Integrated Products

Specifications of DS3988T+T&R

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

Figure 1. Per Channel Logic Diagram
The DS3988 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 (PC
board) design easy to implement. The push-pull drive
scheme also provides an efficient DC-to-AC conversion
and produces near-sinusoidal waveforms.
Each DS3988 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 cen-
ter tap on the primary side that is connected to a DC
voltage supply. The DS3988 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 accu-
rately 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
PHASED LAMP FREQUENCY
[20.48MHz TO 40.96MHz]
512 x LAMP FREQUENCY
CHANNEL ENABLE
CHANNEL FAULT
[40kHz TO 80kHz]
DPWM SIGNAL
RMS
) AC waveform that is required to power
Detailed Description
1 OF 8 CHANNELS
CONTROLLER
DIGITAL
CCFL
_____________________________________________________________________
256 LAMP CYCLE
256 LAMP CYCLE
Fluorescent Lamp Controller
INTEGRATOR
INTEGRATOR
LAMP REGULATION
RMS
LAMP OVERCURRENT
LSE BIT AT CR1.0
LAMP OUT
8-Channel Cold-Cathode
on the DS3988. The DS3988 compares the peak resistor
voltage against an internal reference voltage to deter-
mine the duty cycle for the MOSFET gates. Each CCFL
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 DS3988 uses an I
communication with the on-board EEPROM configura-
tion registers and user memory. The configuration regis-
ters—four Soft-Start Profile registers (SSP1/2/3/4) and
two Control Registers (CR1/2)—allow the user to cus-
tomize many DS3988 parameters such as the soft-start
ramp rate, the lamp and dimming frequency sources,
fault-monitoring options, and channel enabling/disabling.
The eight bytes of nonvolatile user memory can be used
to store manufacturing data such as date codes, serial
numbers, or product identification numbers.
The device is shipped from the factory with the configu-
ration registers programmed to a set of default configu-
ration parameters. To inquire about custom factory
programming, email [e-mail].
OVERVOLTAGE
EEPROM Registers and I
2.0V
1.0V
400mV
1.0V
DRIVERS
GATE
2
C-compatible serial interface for
DETECT/
DETECT
DS3988
HOLD
PEAK
PEAK
Serial Interface
2
C-Compatible
OVD
OVERVOLTAGE
DETECTION
LCM
LAMP CURRENT
MONITOR
G
G
B
A
MOSFET
GATE
DRIVERS
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