19-2783; Rev 0; 4/03
High-Efficiency, 26V Step-Up Converter
for White LED Main and Subdisplay Backlighting
General Description
The MAX1582 drives up to six white LEDs in series with
a constant current to provide display backlighting for
two (main and sub-) displays in cell phones and other
hand-held devices. This configuration eliminates the
need for ballast resistors and expensive factory calibra-
tion. The proprietary dual-output, step-up pulse-width
modulation (PWM) converter includes a 30V, low R
DSON
N-channel MOSFET switch for high efficiency and maxi-
mum battery life.
The MAX1582 utilizes 1MHz current-mode PWM control
to allow small input and output capacitors and a small
inductor, while minimizing ripple on the input supply and
avoiding interference to sensitive circuitry in the equip-
ment. Integrated overvoltage protection eliminates the
need for an external zener diode to protect the IC from
open circuit. Flexible dimming control utilizes either an
analog control signal or direct digital PWM control with-
out external RC filtering. This also increases dimming
accuracy at low brightness levels. The PWM dimming
signal can be any frequency from 200Hz to 200kHz.
Soft-start eliminates inrush current during startup.
The MAX1582 is available in tiny 4
✕
4 chip-scale
(UCSP™) and 12-pin thin QFN packages.
KIT
ATION
EVALU
BLE
AVAILA
Features
o
Accurate Current Regulation for Uniform
Illumination
o
Lights Up Two LED Sections for Main and
Subdisplays
o
Up to 84% Efficiency
o
Internal High-Power, 30V MOSFET
o
Low 15mV
P-P
Input Ripple
o
Flexible Dimming Control
Analog DAC Controlled
Direct-Digital PWM (No RC Required)
from 200Hz to 200kHz
o
Overvoltage Protection to Eliminate Zener Diode
o
Constant 1MHz PWM Operation
o
Low-Profile Inductor and Capacitors
o
Soft-Start Eliminates Inrush Current
o
2.6V to 5.5V Input
o
0.01µA (typ) Shutdown Current
o
Tiny UCSP (2.1mm
✕
2.1mm
✕
0.61mm) and Thin
QFN (4mm
✕
4mm) Packages
MAX1582
Applications
Cell Phones with One or Two Displays
Smart Phones, Palmtops, and Wireless
Handhelds
Other Hand-Held Devices with Dual Displays
PART
MAX1582ETC
Ordering Information
TEMP RANGE
PIN-PACKAGE
TOP
MARK
AACE
1582EBE
-40°C to +85°C 12 Thin QFN-EP*
MAX1582EBE-T -40°C to +85°C 16 UCSP-16
*EP
= Exposed paddle.
Typical Application Circuit
INPUT
2.6V TO 5.5V
2.2µF
22µH
UCSP is a trademark of Maxim Integrated Products, Inc.
Pin Configurations
OUT1
10
9
OUT2
CS
EN2
8
7
4
COMP
5
GND
6
EN1
V+
VP
LX
PGND
12
V+
VP
CTRL
1
2
3
TOP VIEW
MAX1582
OUT1
0.1µF
2 TO 4 LEDS
MAIN
DISPLAY
11
ANALOG OR
DIRECT PWM
DIMMING
CTRL
PGND
EN1
EN2
COMP
CS
GND
OUT2
MAX1582
2 TO 3 LEDS
SUB-
DISPLAY
0.022µF
7.5Ω
4mm x 4mm
THIN QFN
Pin Configurations continued at end of data sheet.
________________________________________________________________
Maxim Integrated Products
1
For pricing, delivery, and ordering information, please contact Maxim/Dallas Direct! at
1-888-629-4642, or visit Maxim’s website at www.maxim-ic.com.
LX
High-Efficiency, 26V Step-Up Converter
for White LED Main and Subdisplay Backlighting
MAX1582
ABSOLUTE MAXIMUM RATINGS
V+, VP, CTRL to GND............................................-0.3V to +6.0V
PGND to GND .......................................................-0.3V to +0.3V
LX, OUT1 to GND ...................................................-0.3V to +30V
OUT2 to GND .........................................................-0.3V to +14V
COMP, CS, EN1, EN2 to GND ....................-0.3V to (V
V+
+ 0.3V)
I
LX ....................................................................................................
1A
RMS
Continuous Power Dissipation (T
A
= +70°C)
12-Pin Thin QFN (derate 16.9mW/°C above +70°C) ....1349mW
16-Pin UCSP (derate 6.5mW/°C above +70°C)..............518mW
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
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.
ELECTRICAL CHARACTERISTICS
(V
V+
= +3.0V, V
OUT1
= 20V, L1 = 22µH, C
OUT
= 0.1µF, C
COMP
= 0.022µF, R
SENSE
= 7.5Ω, V
CTRL
= +1.5V, EN1 = EN2 = V+,
T
A
=
0°C to +85°C,
unless otherwise noted. Typical values are at T
A
= +25°C.) (Note 1)
PARAMETER
Supply Voltage
Undervoltage Lockout (UVLO)
Threshold
UVLO Hysteresis
Quiescent Current
Shutdown Supply Current
Overvoltage Lockout (OVLO)
Threshold
OVLO Hysteresis
V
OUT1
= +26V, EN1 = EN2 = V+
OUT1 Input Bias Current
OUT1 = V+, EN1 = EN2 = GND
(Note 2)
T
A
= +25°C
T
A
= +85°C
(V
V+
-
V
DIODE
)
0.095
T
A
= +25°C
T
A
= +85°C
290
32
0.80
PWM mode
Pulse skipping
CTRL = V+, CS = GND
91
0.100
0.01
1
500
50
1.0
12
0
94
780
82
1.25
20
No switching, V
CTRL
= V
CS
= +0.25V
EN1 = EN2 = GND, OUT1 = V+
T
A
= +25°C
T
A
= +85°C
26
V+ rising or falling
CONDITIONS
MIN
2.6
2.10
2.38
40
0.40
0.01
0.1
27
2
40
0.01
0.05
25.5
V
65
1
µA
29
0.56
1
TYP
MAX
5.5
2.55
UNITS
V
V
mV
mA
µA
V
V
Output Voltage Range
ERROR AMPLIFIER
CTRL to CS Regulation
CS Input Bias Current
CTRL Input Resistance
CS to COMP Transconductance
OSCILLATOR
Operating Frequency
Minimum Duty Cycle
Maximum Duty Cycle
V
CTRL
= +1.0V, V
V+
= +2.6V to +5.5V
V
CS
= V
CTRL
/ 10
0 < V
CTRL
< +1V
V
COMP
= +1.0V
0.106
1
V
µA
kΩ
µS
MHz
%
%
2
_______________________________________________________________________________________
High-Efficiency, 26V Step-Up Converter
for White LED Main and Subdisplay Backlighting
ELECTRICAL CHARACTERISTICS (continued)
(V
V+
= +3.0V, V
OUT1
= 20V, L1 = 22µH, C
OUT
= 0.1µF, C
COMP
= 0.022µF, R
SENSE
= 7.5Ω, V
CTRL
= +1.5V, EN1 = EN2 = V+,
T
A
=
0°C to +85°C,
unless otherwise noted. Typical values are at T
A
= +25°C.) (Note 1)
PARAMETER
N-CHANNEL SWITCH
LX On-Resistance
LX Leakage Current
LX Current Limit
OUT1 to OUT2 On-Resistance
OUT2 to CS On-Resistance
OUT1 to OUT2 Leakage Current
OUT2 to CS Leakage Current
EN1 and EN2 Logic Input Voltage
High
EN1 and EN2 Logic Input Voltage
Low
EN1 and EN2 Input Leakage
V
LX
= +28V
Duty cycle = 90%
EN1 = GND, EN2 = V+
EN1 = V+, EN2 = GND
EN1 = EN2 = V+, V
OUT1
= 25V, V
OUT2
= +9V, T
A
= +85°C
EN1 = EN2 = V+, V
OUT2
= 12V, V
CS
= 0, T
A
= +85°C
+2.6V < V
V+
< +5.5V
+2.6V < V
V+
< +5.5V
V
V+
= V
EN1
= V
EN2
= +5.5V
T
A
= +25°C
T
A
= +85°C
0.02
0.1
1.6
0.6
1
T
A
= +25°C
T
A
= +85°C
450
1.50
0.01
0.02
650
2.5
2.5
0.05
0.05
950
2.25
5
Ω
µA
mA
Ω
Ω
µA
µA
V
V
µA
CONDITIONS
MIN
TYP
MAX
UNITS
MAX1582
MAIN AND SUBDISPLAY ON/OFF SWITCHES
ELECTRICAL CHARACTERISTICS
(V
V+
= +3.0V, V
OUT1
= +20V, L1 = 22µH, C
OUT
= 0.1µF, C
COMP
= 0.022µF, R
SENSE
= 7.5Ω, V
CTRL
= +1.5V, EN1 = EN2 = V+,
T
A
=
-40°C to +85°C,
unless otherwise noted.) (Notes 1, 3)
PARAMETER
Supply Voltage
Undervoltage Lockout (UVLO)
Threshold
Quiescent Current
Overvoltage Lockout (OVLO)
Threshold
OUT1 Input Bias Current
Output Voltage Range
ERROR AMPLIFIER
CTRL to CS Regulation
CTRL Input Resistance
CS to COMP Transconductance
OSCILLATOR
Operating Frequency
0.75
1.30
MHz
V
CTRL
= +1.0V, V
V+
= +2.6V to +5.5V
0 < V
CTRL
< +1.0V
V
COMP
= 1.0V
0.093
290
32
0.107
780
85
V
kΩ
µS
V+ rising or falling
No switching, V
C
= +0.25V
Rising
V
OUT1
= +26V, EN1 = EN2 = V+
(Note 2)
26
20
(V
V+
-
V
DIODE
)
CONDITIONS
MIN
2.6
2.10
MAX
5.5
2.55
0.56
29
65
25.5
UNITS
V
V
mA
V
µA
V
_______________________________________________________________________________________
3
High-Efficiency, 26V Step-Up Converter
for White LED Main and Subdisplay Backlighting
MAX1582
ELECTRICAL CHARACTERISTICS (continued)
(V
V+
= +3.0V, V
OUT1
= +20V, L1 = 22µH, C
OUT
= 0.1µF, C
COMP
= 0.022µF, R
SENSE
= 7.5Ω, V
CTRL
= +1.5V, EN1 = EN2 = V+,
T
A
=
-40°C to +85°C,
unless otherwise noted.) (Notes 1, 3)
PARAMETER
Maximum Duty Cycle
N-CHANNEL SWITCH
LX On-Resistance
LX Current Limit
Duty cycle = 90%
450
2.25
950
Ω
mA
CONDITIONS
CTRL = V+, CS = GND
MIN
91
MAX
UNITS
%
Note 1:
Limits are 100% production tested at T
A
= +25°C for UCSP parts. Limits over the entire operating temperature range are
guaranteed by design and characterization but are not production tested.
Note 2:
The minimum output voltage is the input voltage minus the forward voltage drop of the Schottky diode:
V
OUT(MIN)
= V
V+
- V
DIODE
Note 3:
Specifications to -40°C are guaranteed by design and not production tested.
Typical Operating Characteristics
(See the
Typical Applications Circuit,
V
V+
= V
VP
= 3.6V, I
LED
= 15mA, L1 = 22µH, C
OUT1
= 0.1µF, C
COMP
= 0.022µF, R
SENSE
= 7.5Ω,
V
CTRL
= 1.5V, 4 LEDs, T
A
= +25°C, unless otherwise noted.)
EFFICIENCY vs. LED CURRENT
(vs. NUMBER of LEDs)
MAX1582 toc01
EFFICIENCY vs. LED CURRENT
(vs. INPUT VOLTAGE)
MAX1582 toc02
EFFICIENCY vs. LED CURRENT
(vs. INDUCTANCE)
MAX1582 toc03
100
90
6 LEDs
EFFICIENCY (%)
80
70
4 LEDs
60
50
40
0
5
10
LED CURRENT (mA)
15
2 LEDs
100
90
EFFICIENCY (%)
80
70
60
50
40
4.2 V
IN
3.6 V
IN
100
90
10µH
EFFICIENCY (%)
80
70
60
50
40
47µH
4.7µH
22µH
2.7 V
IN
20
0
5
10
LED CURRENT (mA)
15
20
0
5
10
LED CURRENT (mA)
15
20
INPUT RIPPLE vs. INDUCTANCE
MAX1582 toc04
INPUT RIPPLE SPECTRUM
MAX1582 toc05
LED CURRENT vs. DIRECT-PWM
DIMMING DUTY CYCLE
MAX1582 toc06
40
35
INPUT RIPPLE (mV
P-P
)
30
25
20
15
10
5
0
0
5
6
5
INPUT RIPPLE (mV
RMS
)
4
3
2
1
0
25
20
LED CURRENT (mA)
15
10
5
V
CTRL
= SQUARE WAVE
200Hz < FREQ < 200kHz
0
0
1
2
3
4
5
6
7
8
9
10
0
10 20 30 40 50 60 70 80 90 100
DIRECT-PWM DIMMING DUTY CYCLE (%)
FREQUENCY (MHz)
10 15 20 25 30 35 40 45 50
INDUCTANCE (µH)
4
_______________________________________________________________________________________
High-Efficiency, 26V Step-Up Converter
for White LED Main and Subdisplay Backlighting
Typical Operating Characteristics (continued)
(See the
Typical Applications Circuit,
V
V+
= V
VP
= 3.6V, I
LED
= 15mA, L1 = 22µH, C
OUT1
= 0.1µF, C
COMP
= 0.022µF, R
SENSE
= 7.5Ω,
V
CTRL
= 1.5V, 4 LEDs, T
A
= +25°C, unless otherwise noted.)
SWITCHING WAVEFORMS
MAX1582 toc07
MAX1582
DIRECT-PWM DIMMING
MAX1582 toc08
V
IN
10mV/div
V
CTRL
32kHz
1V/div
0V
V
IN
50mV/div
I
IN
50mA/div
0mA
V
OUT
100mV/div
V
LX
10V/div
V
IN = 3.8V Li+ BATTERY
V
OUT
5V/div
0V
500ns/div
50µs/div
Pin Description
PIN
QFN
1
2
3
UCSP
A1
A2
A3
NAME
V+
VP
CTRL
FUNCTION
Input Voltage Supply. Input voltage range is 2.6V to 5.5V. Connect a 2.2µF capacitor from V+ to
PGND.
High-Current Input Supply. Connect to V+.
Brightness Control Input. LED brightness is controlled by the voltage applied to CTRL. Varying the
voltage from 0 to +1.62V adjusts the brightness from dim to bright, respectively. Any voltage
above +1.62V does not increase brightness.
Compensation Input. Connect a 0.022µF capacitor (C
COMP
) from COMP to GND. C
COMP
stabilizes the converter and controls soft-start. C
COMP
discharges to GND when in shutdown.
Ground. Connect to PGND at a single point near the IC.
Enable 1 Input. Drive EN1 high to enable the main-display LEDs. Pull EN1 low to turn off the main-
display LEDs. Pull both EN1 and EN2 low to place the IC in low-current shutdown mode.
Enable 2. Drive EN2 high to enable the subdisplay LEDs. Pull EN2 low to turn off the subdisplay
LEDs. Pull both EN1 and EN2 low to place the IC in low-current shutdown mode.
Current-Sense Feedback Input. Connect a resistor (R
SENSE
) from CS to GND to set the LED bias
current. The voltage at CS regulates to V
CTRL
/ 10 or +0.162V, whichever is lower.
Display Switch Output. OUT2 is internally connected to CS when only the main display is lit. OUT2
is internally connected to OUT1 when only the subdisplay is lit. OUT2 is high impedance when
both displays are lit and when the IC is shut down.
Overvoltage Sense. When V
OUT1
is greater than 27V, the internal N-channel MOSFET turns off until
V
OUT1
drops below 25V, then the IC reenters soft-start. Connect a 0.1µF capacitor from OUT1 to
PGND.
Inductor Connection. During shutdown, this pin is high impedance.
Power Ground. Connect to GND at a single point near the IC.
Exposed Paddle. Connect directly to GND and PGND under the IC.
4
5
6
7
8
A4
B4
C4
D4
D3
COMP
GND
EN1
EN2
CS
9
D2
OUT2
10
11
12
EP
D1
C1
B1
—
OUT1
LX
PGND
EP
_______________________________________________________________________________________
5
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