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MAX8722AEEG+T

P1-P3P4-P6P7-P9P10-P12P13-P15P16-P18P19-P20
For pricing, delivery, and ordering information, please contact Maxim Direct at 1-888-629-4642,
or visit Maxim's website at www.maxim-ic.com.
General Description
The MAX8722A integrated backlight controller is opti-
mized to drive cold-cathode fluorescent lamps (CCFLs)
using a full-bridge resonant inverter architecture.
Resonant operation maximizes striking capability and
provides near-sinusoidal waveforms over the entire
input range to improve CCFL lifetime. The controller
operates over a wide input voltage range (4.6V to 28V)
with high power to light efficiency. The device also
includes safety features that effectively protect against
many single-point fault conditions including lamp-out
and short-circuit faults.
The MAX8722A achieves 10:1 dimming range by “chop-
ping” the lamp current on and off using a digital pulse-
width modulation (DPWM) method. The DPWM frequency
can be accurately adjusted with a resistor or synchro-
nized to an external signal. The brightness is controlled
by an analog voltage on the CNTL pin. The device direct-
ly drives the four external n-channel power MOSFETs of
the full-bridge inverter. An internal 5.3V linear regulator
powers the MOSFET drivers, the DPWM oscillator, and
most of the internal circuitry. The MAX8722A is available
in a low-cost, 24-pin QSOP package and operates over a
-40°C to +85°C temperature range.
Applications
Notebook Computer Displays
LCD Monitors
LCD TVs
Features
♦ Synchronized to Resonant Frequency
Longer Lamp Life
Guaranteed Striking Capability
High Power to Light Efficiency
♦ Wide Input Voltage Range (4.6V to 28V)
♦ Input-Voltage Feed-Forward for Excellent Line
Rejection
♦ Accurate Dimming Control with Analog Interface
♦ 10:1 Dimming Range
♦ Adjustable Accurate DPWM Frequency with Sync
Function
♦ Adjustable Lamp Current Rise and Fall Time
♦ Secondary Voltage Limit Reduces Transformer
Stress
♦ Lamp-Out Protection with Adjustable Timeout
♦ Secondary Overcurrent Protection with
Adjustable Timeout
♦ Low-Cost 24-Pin QSOP Package
MAX8722A
Low-Cost CCFL Backlight Controller
________________________________________________________________ Maxim Integrated Products 1
Ordering Information
19-3321; Rev 0; 10/05
PART
TEMP RANGE PIN-PACKAGE
PKG
CODE
MAX8722AEEG
-40°C to +85°C
24 QSOP
E24-1
MAX8722A
GND
GH2
LX2
BST2
BST1
LX1
GH1
GL1
V
DD
BATT
IFB
VFB
GL2
ISEC
CNTL
ILIM
FREQ
SYNC
PGND
COMP
V
IN
V
CC
DPWM
TFLT
V
CC
V
CC
SHDN
Minimal Operating Circuit
24
23
22
21
20
19
18
17
1
2
3
4
5
6
7
8
GND
V
CC
V
DD
PGNDTFLT
ILIM
BATT
TOP VIEW
GL2
GL1
GH1
LX1FREQ
SYNC
DPWM
CNTL
16
15
14
13
9
10
11
12
BST1
BST2
LX2
GH2ISEC
VFB
IFB
COMP
QSOP
MAX8722A
SHDN
Pin Configuration
MAX8722A
Low-Cost CCFL Backlight Controller
2 _______________________________________________________________________________________
ABSOLUTE MAXIMUM RATINGS
ELECTRICAL CHARACTERISTICS
(Circuit of Figure 1. V
BATT
= 12V, V
CC
= V
DD
, V
SHDN
= 5.3V, T
A
= 0°C to +85°C. Typical values are at T
A
= +25°C, unless otherwise noted.)
Stresses beyond those listed under “Absolute Maximum Ratings” may cause permanent damage to the device. These are stress ratings only, and functional
operation of the device at these or any other conditions beyond those indicated in the operational sections of the specifications is not implied. Exposure to
absolute maximum rating conditions for extended periods may affect device reliability.
BATT to GND..........................................................-0.3V to +30V
BST1, BST2 to GND ...............................................-0.3V to +36V
BST1 to LX1, BST2 to LX2 ........................................-0.3V to +6V
CNTL, FREQ, SYNC, V
CC
, V
DD
to GND ...................-0.3V to +6V
COMP, DPWM, ILIM, TFLT to GND ............-0.3V to (V
CC
+ 0.3V)
GH1 to LX1 ..............................................-0.3V to (V
BST1
+ 0.3V)
GH2 to LX2 ..............................................-0.3V to (V
BST2
+ 0.3V)
GL1, GL2 to GND .......................................-0.3V to (V
DD
+ 0.3V)
IFB, ISEC, VFB to GND................................................-3V to +6V
SHDN to GND...........................................................-0.3V to +6V
PGND to GND .......................................................-0.3V to +0.3V
Continuous Power Dissipation (T
A
= +70°C)
24-Pin QSOP (derate 9.5mW/°C above +70°C)........761.9mW
Operating Temperature Range ...........................-40°C to +85°C
Junction Temperature......................................................+150°C
Storage Temperature Range .............................-65°C to +150°C
Lead Temperature (soldering, 10s) .................................+300°C
PARAMETER CONDITIONS
MIN
TYP
UNITS
V
CC
= V
DD
= V
BATT
4.6 5.5
BATT Input Voltage Range
V
CC
= V
DD
= open 5.5
28.0
V
V
BATT
= 28V 1 2
BATT Quiescent Current V
SHDN
= V
CC
,
V
IFB
= 1V
V
BATT
= V
CC
= 5V 2
mA
BATT Quiescent Current,
Shutdown
SHDN = GND 6 20 µA
V
CC
Output Voltage, Normal
Operation
V
SHDN
= 5.5V, 6V < V
BATT
< 28V,
0 < I
LOAD
< 10mA
5.25 5.40 5.55
V
V
CC
Output Voltage, Shutdown SHDN = GND, no load 3.5 4.6 5.5 V
V
CC
rising (leaving lockout)
4.58
V
CC
Undervoltage-Lockout
Threshold
V
CC
falling (entering lockout) 4.0
V
V
CC
Undervoltage-Lockout
Hysteresis
200
mV
GH1, GH2, GL1, GL2 On-
Resistance, High
I
TEST
= 10mA, V
CC
= V
DD
= 5.3V 20 37 Ω
GH1, GH2, GL1, GL2 On-
Resistance, Low
I
TEST
= 10mA, V
CC
= V
DD
= 5.3V 10 20 Ω
GH1, GH2, GL1, GL2 Maximum
Output Current
0.3 A
BST1, BST2 Leakage Current V
BST
_ = 12V, V
LX
_ = 7V 5 µA
Resonant Frequency Range Guaranteed by design 30 80 kHz
Minimum Off-Time
340 470 600
ns
Maximum Off-Time 24 33 43 µs
Current-Limit Threshold
LX1 to PGND, LX2 to PGND
(Fixed)
ILIM = V
CC
180 200 220
mV
V
ILIM
= 0.5V 80
100 120
Current-Limit Threshold
LX1 to PGND, LX2 to PGND
(Adjustable)
V
ILIM
= 2.0V
370 400 430
mV
MAX8722A
Low-Cost CCFL Backlight Controller
_______________________________________________________________________________________ 3
ELECTRICAL CHARACTERISTICS (continued)
(Circuit of Figure 1. V
BATT
= 12V, V
CC
= V
DD
, V
SHDN
= 5.3V, T
A
= 0°C to +85°C. Typical values are at T
A
= +25°C, unless otherwise noted.)
PARAMETER CONDITIONS
MIN TYP MAX
UNITS
Zero-Current Crossing Threshold
LX1 to GND, LX2 to GND
1612mV
Current-Limit Leading Edge
Blanking
240 350 460
ns
IFB Input Voltage Range -2 +2 V
IFB Regulation Point
770 790 810
mV
0 < V
IFB
< 2V -2 +2
IFB Input Bias Current
-2V < V
IFB
< 0
-150
µA
IFB Lamp-Out Threshold
560 600 640
mV
IFB to COMP Transconductance
0.5V < V
COMP
< 4V 60
100 160
µS
COMP Output Impedance 71018MΩ
COMP Discharge Current During
Overvoltage or Overcurrent Fault
V
IFB
= 800mV, V
ISEC
= 2V
1200
µA
COMP Discharge Current During
DPWM Off-Time
CNTL = GND, V
COMP
= 2V
100
µA
DPWM Rising to Falling Ratio V
IFB
= 0 2.5 —
ISEC Overcurrent Threshold
1.15 1.21 1.28
V
ISEC Input Bias Current 0 < V
ISEC
< 2V
-0.3 +0.3
µA
VFB Input Bias Current -4V < V
VFB
< +4V -25
+25
µA
VFB Overvoltage Threshold 2.2 2.3 2.4 V
R
FREQ
= 100kΩ
343
R
FREQ
= 169kΩ
204 209 214
DPWM Chopping Frequency
R
FREQ
= 340kΩ
106
Hz
DPWM Input Low Voltage SYNC = V
CC
, R
FREQ
= 169kΩ 0.8 V
DPWM Input High Voltage SYNC = V
CC
, R
FREQ
= 169kΩ 2.1 V
DPWM Input Hysteresis SYNC = V
CC
, R
FREQ
= 169kΩ
100
mV
DPWM Input Bias Current SYNC = V
CC
, R
FREQ
= 169kΩ
-0.3 +0.3
µA
DPWM Output Low Resistance SYNC = GND, FREQ = V
CC
2.4 kΩ
DPWM Output High Resistance SYNC = V
CC
, FREQ = V
CC
2.4 kΩ
SYNC Input Low Voltage 0.8 V
SYNC Input High Voltage 2.1 V
SYNC Input Hysteresis
100
mV
SYNC Input Bias Current V
SYNC
= 2V
-0.3 +0.3
µA
SYNC Input Frequency Range 10 50 kHz
CNTL Minimum Duty-Cycle
Threshold
0.20 0.23 0.26
V
CNTL Maximum Duty-Cycle
Threshold
1.9 2.0 2.1 V
CNTL Input Current 0 < V
CNTL
< V
CC
-0.1 +0.1
µA
DPWM ADC Resolution Guaranteed monotonic 5 Bits
P1-P3P4-P6P7-P9P10-P12P13-P15P16-P18P19-P20

MAX8722AEEG+T

Mfr. #:
Buy MAX8722AEEG+T
Manufacturer:
Maxim Integrated
Description:
Display Drivers & Controllers CCFL Backlight Controller
Lifecycle:
New from this manufacturer.
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