MAX1895 Datasheet, PDF (1/31 Pages) Maxim Integrated Products – High-Efficiency, Wide Brightness Range, CCFL Backlight Controllers

19-2157; Rev 1; 10/02
High-Efficiency, Wide Brightness
Range, CCFL Backlight Controllers
General Description
The MAX1895/MAX1995 integrated controllers are opti-
mized to drive cold-cathode fluorescent lamps (CCFL)
using a synchronized full-bridge inverter architecture.
Synchronized drive provides near sinusoidal wave-
forms over the entire input range to maximize the life of
CCFLs. The controllers also operate over a wide input
voltage range with high efficiency and broad dimming
range.
The MAX1895/MAX1995 include safety features that
limit the transformer secondary voltage and protect
against single-point fault conditions including lamp-out
and short-circuit faults.
The MAX1895/MAX1995 regulate the CCFL brightness
in three ways: linearly controlling the lamp current, digi-
tal pulse-width modulating (DPWM) the lamp current, or
using both methods simultaneously to achieve the
widest dimming range (>30:1). CCFL brightness can
be controlled with either an analog voltage (both
MAX1895 and MAX1995) or a two-wire SMBus™ com-
patible interface (MAX1895 only).
The MAX1895/MAX1995 directly drive the four external
N-channel power MOSFETs of the full-bridge inverter.
An internal 5.3V linear regulator powers the MOSFET
drivers, the synchronizable DPWM oscillator, and most
of the internal circuitry. The MAX1895/MAX1995 are
available in the space-saving 28-pin thin QFN package
and operate over the -40°C to +85°C temperature
range.
Applications
Notebook Computers
Car Navigation Displays
LCD Monitors
Point-of-Sale Terminals
Portable Display Electronics
Features
o Synchronized-to-Resonant Frequency
Good Crest Factor for Longer Lamp Life
Ensures Maximum Strike Capability
o High Power to Light Efficiency
o Wide Dimming Range (3 Methods)
Lamp Current Adjust: >3 to 1
Digital PWM (DPWM): >10 to 1
Combined: >30 to 1
o Feed-Forward for Fast Response to Step Change
of Input Voltage
o Wide Input Voltage Range (4.6V to 28V)
o Transformer Secondary Voltage Limiting to
Reduce Transformer Stress
o Lamp-Out Protection with 2s Timeout
o Short-Circuit and Other Single-Point Fault
Protections
o Synchronizable DPWM Frequency
o Dual-Mode Brightness Control Interface
SMBus Serial Interface (MAX1895 Only)
Analog Interface (Both Devices)
o High-Accuracy Analog Interface
Separate 100% Brightness Voltage Reference
Pin (CRFSDA)
Separate Minimum Lamp-Current Set-Point Pin
(MINDAC)
o Small Footprint 28-Pin Thin QFN (5mm x 5mm)
Package
Pin Configurations
TOP VIEW
Ordering Information
PART
MAX1895ETI
MAX1895EGI*
MAX1995ETI
MAX1995EGI*
TEMP RANGE
-40°C to +85°C
-40°C to +85°C
-40°C to +85°C
-40°C to +85°C
*Contact factory for availability.
PIN-PACKAGE
28 Thin QFN 5 ✕ 5
28 QFN 5 ✕ 5
28 Thin QFN 5 ✕ 5
28 QFN 5 ✕ 5
Pin Configurations continued at end of data sheet.
SMBus is a trademark of Intel Corp.
ILIM 1
REF 2
MINDAC 3
GND 4
MODE 5
CRF/SDA 6
CTL/SCL 7
MAX1895
21 GH2
20 LX2
19 BST2
18 BST1
17 LX1
16 GH1
15 GL1
THIN QFN
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