MAXIM MAX1698, MAX1698A Technical data
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General Description
The MAX1698 and MAX1698A are efficient drivers for
white or color LEDs. They are ideal for large LED backlit
displays in PDAs and laptop computers. Numerous
benefits include greater simplicity, lower cost, higher
efficiency, longer bulb life, and greater reliability when
compared to fluorescent (CCFL) and electroluminescent (EL) lamps.
The MAX1698/MAX1698A are switch-mode boost controllers in which LED current, rather than output voltage,
is regulated The devices drive series-connected LEDs
with a controlled current that is measured with a typically 15Ω sense resistor, not an expensive fractional-ohm
value. LED current control and dimming are accomplished with an adjust input (ADJ). For larger light output, multiple LED banks can be connected in parallel
with up to 5W total output power.
The MAX1698A has a higher, and more accurately
specified, CS current limit than the MAX1698 for higherpower applications of 5W or more. Both devices are
supplied in a space-saving 10-pin µMAX package that
occupies half the space of an 8-pin SO. An evaluation
kit (MAX1698EVKIT) is available to speed designs.
Applications
Battery-Powered Backlight Applications
Backlight for LCD Panels
Notebook PCs
Handy Terminals
PDAs
Features
♦ Over 90% Efficiency
♦ Lossless, Adjustable LED Brightness
♦ Space-Saving 10-Pin µMAX Package
♦ Simpler, Lower Cost, More Reliable Compared
to CCFL or EL Backlights
♦ Up to 5W Output Power
MAX1698/MAX1698A
High-Efficiency Step-Up
Current Regulator for LEDs
________________________________________________________________ Maxim Integrated Products 1
Typical Operating Circuit
19-1621; Rev 2; 2/07
Pin Configuration
Ordering Information
PART T EM P RA N G E
MAX1698EUB -40°C to +85°C
MAX1698AEUB -40°C to +85°C
PIN PA C K A G E
10µMAX
10µMAX
PKG
CODE
U10-2
U10-2
TOP VIEW
V
SHDN
REF
1
CC
2
MAX1698
3
MAX1698A
4
5
µMAX
10
EXT
9
CS
8
PGND
7
GNDADJ
6
FBGND
V
CC
SHDN
REF
ADJ
GND
L
MAX1698
MAX1698A
EXT
CS
PGND
FB
V
BATT
V
CC
OFF
ON
D1
I
LED
R
FB
R
N
V
OUT
C
OUT
MAX1698/MAX1698A
High-Efficiency Step-Up
Current Regulator for LEDs
2 _______________________________________________________________________________________
ABSOLUTE MAXIMUM RATINGS
ELECTRICAL CHARACTERISTICS
(VCC= +3.3V, TA= 0°C to +85°C, unless otherwise noted. Typical values are at TA= +25°C.)
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.
VCC, SHDN to GND..................................................-0.3V to +6V
EXT, FB, CS, ADJ, REF to GND..................-0.3V to (V
CC
+ 0.3V)
GND to PGND.....................................................................±0.3V
Continuous Power Dissipation (T
A
= +70°C)
10-Pin µMAX (derate 5.6mW/°C above +70°C) ............444mW
Operating Temperature Range ...........................-40°C to +85°C
Junction Temperature......................................................+150°C
Storage Temperature Range .............................-65°C to +150°C
Lead Temperature Range (soldering, 10s)......................+300°C
FB = GND, ADJ = REF, CS = GND
FB = GND, ADJ = REF
Rising edge
FB = GND
VFB= 0.3V
ADJ = REF
V
ADJ
= 100mV
CONDITIONS
mV30 50 70ADJ Start Threshold
µs10 15 20t
ON(MAX)
Maximum On Time
µs0.8 1.0 1.2t
OFF(MIN)
Minimum Off Time
A
RMS
0.8I
CS
CS Input Current
A
0.8 1.5 2.5
CS Trip Current
V2.25 2.4 2.55Undervoltage Lockout
µA260 500I
CC
V2.7 5.5V
CC
Supply Voltage
Quiescent Supply Current
mV80Undervoltage Hysteresis
285 300 315
mV
18 24 30
V
FB
FB Regulation Voltage
UNITSMIN TYP MAXSYMBOLPARAMETER
VFB= 300mV nA-15 15I
FB
FB Input Bias Current
V0.03 REFV
ADJ
ADJ Input Range
ADJ Input Bias Current I
ADJ
ADJ = REF -50 50 nA
Shutdown Supply Current
SHDN = GND
0.01 1 µA
REF Output Voltage V
REFIREF
= 0 1.20 1.25 1.30 V
REF Load Regulation ∆V
REFIREF
= 0 to 150µA -2 -25 mV
REF Short-Circuit Current REF = GND 0.45 1 mA
REF Power-Supply Rejection
Ratio
PSRR VCC= 2.7V to 5.5V +0.3 +2 mV/V
EXT Driver Sink/Source Current VCC= 5V, EXT = 2V 0.2 A
EXT Driver On-Resistance VCC= 5V 8 Ω
SHDN Input High Voltage
V
IH
VCC= 2.7V to 5.5V 2 V
SHDN Input Low Voltage
V
IL
VCC= 2.7V to 5.5V 0.8 V
SHDN Input Bias Current
I
SHDN
VCC= 2.7V to 5.5V -1 1 µA
2.0 2.4 2.8
MAX1698
MAX1698A
MAX1698/MAX1698A
High-Efficiency Step-Up
Current Regulator for LEDs
_______________________________________________________________________________________ 3
ELECTRICAL CHARACTERISTICS
(VCC= +3.3V, TA= -40°C to +85°C, unless otherwise noted.) (Note 1)
CONDITIONS
VV
CC
Supply Voltage 2.7 5.5
UNITSMIN MAXSYMBOLPARAMETER
FB = GND
2.0 3.0
Minimum Off Time t
OFF(MIN)
FB = GND, ADJ = REF 0.6 1.4 µs
Maximum On Time t
ON(MAX)
FB = GND, ADJ = REF, CS = GND 921µs
ADJ Start Threshold 25 75 mV
FB Input Bias Current I
FB
VFB= 300mV -20 20 nA
ADJ Input Bias Current I
ADJ
ADJ = REF -50 50 nA
Shutdown Supply Current
SHDN = GND
1 µA
REF Output Voltage V
REFIREF
= 0 1.17 1.33 V
REF Load Regulation ∆V
REFIREF
= 0 to 150µA -30 mV
REF Short-Circuit Current REF = GND 1 mA
REF Power-Supply Rejection
Ratio
PSRR VCC= 2.7V to 5.5V +2 mV/V
EXT On-Resistance VCC= 5V 8 Ω
SHDN Input High Voltage
V
IH
VCC= 2.7V to 5.5V 2 V
SHDN Input Low Voltage
V
IL
VCC= 2.7V to 5.5V 0.8 V
SHDN Input Bias Current
I
SHDN
VCC= 2.7V to 5.5V -1 1 µA
Note 1: Specifications to -40°C are guaranteed by design, not production tested.
Rising edge VUndervoltage Lockout 2.20 2.65
V
ADJ
= 100mV
ADJ = REF
mV
13 35
V
FB
FB Regulation Voltage
280 320
VFB= 0.3V µAI
CC
Quiescent Supply Current 500
CS Trip Current
0.8 3.0
A
MAX1698A
MAX1698
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