19-2731; Rev 1; 10/03
KIT
ATION
EVALU
BLE
AVAILA
High-Efficiency, 26V Step-Up Converters
for Two to Six White LEDs
General Description
The MAX1561/MAX1599 step-up converters drive up to
six white LEDs with a constant current to provide back-
light in cell phones, PDAs, and other hand-held
devices. The step-up converter topology allows series
connection of the white LEDs so the LED currents are
identical for uniform brightness. This configuration elim-
inates the need for ballast resistors and expensive fac-
tory calibration.
The MAX1561/MAX1599 include an internal, high-volt-
age, low-R
DS(ON)
N-channel MOSFET switch for high
efficiency and maximum battery life. A single Dual
Mode™ input provides a simple means of brightness
adjustment and on/off control. Fast 1MHz (500kHz for
the MAX1599) current-mode, pulse-width modulated
(PWM) operation allows for small input and output
capacitors and a small inductor while minimizing ripple
on the input supply/battery. Programmable soft-start
eliminates inrush current during startup.
Both devices are available in a space-saving, 8-pin 3mm
x 3mm thin DFN package with exposed paddle (EP).
Features
♦
Accurate Current Regulation for Uniform
Illumination
♦
High Efficiency Up to 87%
♦
Flexible Analog or PWM Dimming Control
♦
Up to 900mW Output Power with Internal 30V
MOSFET Switch
♦
Fast 1MHz (MAX1561) or 500kHz (MAX1599) PWM
Operation
♦
Small, Low-Profile External Components
♦
2.6V to 5.5V Input Range
♦
26V (max) Output with Overvoltage Protection
♦
Optimized for Low 15mV
P-P
Input Ripple
♦
Soft-Start with Zero Inrush Current
♦
0.3µA Shutdown Current
♦
Tiny 8-Pin 3mm x 3mm Thin DFN Package
MAX1561/MAX1599
Ordering Information
PART
MAX1561ETA
MAX1599ETA
TEMP RANGE
-40°C to +85°C
-40°C to +85°C
PIN-PACKAGE
8 TDFN-EP*
8 TDFN-EP*
TOP
MARK
ACS
AHG
Applications
Cell Phones and Smart Phones
PDAs, Palmtops, and Wireless Handhelds
e-Books and Subnotebooks
White LED Display Backlighting
*EP
= Exposed paddle.
Typical Operating Circuit
INPUT 2.6V TO 5.5V
OUTPUT UP TO 6 LEDs
IN
LX
OUT
OUT 1
Pin Configuration
TOP VIEW
MAX1561
MAX1599
8 LX
7 PGND
6 GND
5 COMP
PWM OR
ANALOG
DIMMING
MAX1561
MAX1599
CTRL
PGND
IN 2
CTRL 3
CS 4
COMP
GND
CS
3mm
×
3mm
THIN DFN
Dual Mode is a trademark of Maxim Integrated Products, Inc.
________________________________________________________________
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.
High-Efficiency, 26V Step-Up Converters
for Two to Six White LEDs
MAX1561/MAX1599
ABSOLUTE MAXIMUM RATINGS
IN to GND .................................................................-0.3V to +6V
PGND to GND .......................................................-0.3V to +0.3V
LX, OUT to GND .....................................................-0.3V to +30V
CTRL to GND...................-0.3V to the lower of +6V or (V
IN
+ 2V)
COMP, CS to GND.........................................-0.3 to (V
IN
+ 0.3V)
I
LX
.............................................................................................1A
Continuous Power Dissipation (T
A
= +70°C)
3mm x 3mm 8-Pin TDFN
(derate 24.4mW/°C above +70°C) .............................1950mW
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
IN
= 3V, V
OUT
= 20V, C
OUT
= 0.1µF, C
COMP
= 0.15µF, R
SENSE
= 7.5Ω, V
CTRL
= 1.5V, Figure 1,
T
A
= 0°C to +85°C,
unless other-
wise noted. Typical values are at T
A
= +25°C.)
PARAMETER
Supply Voltage
UVLO Threshold
UVLO Hysteresis
Quiescent Current
Shutdown Supply Current
OVLO Threshold
OVLO Hysteresis
OUT Input Bias Current
Output Voltage Range
ERROR AMPLIFIER
CTRL to CS Regulation
CS Input Bias Current
CTRL Input Resistance
CTRL Dual-Mode Threshold
CTRL Dual-Mode Hysteresis
CTRL Shutdown Enable Delay
CS-to-COMP Transconductance
OSCILLATOR
Operating Frequency
Minimum Duty Cycle
Maximum Duty Cycle
MAX1561
MAX1599
PWM mode
Pulse skipping
CTRL = IN, CS = GND
91
0.80
0.4
1.0
0.5
12
0
94
1.25
0.6
MHz
%
%
(Note 2)
V
COMP
= 1.0V
MAX1561
MAX1599
6.5
13.6
32
V
CTRL
= 1V, V
IN
= 2.6V to 5.5V
V
CS
= V
CTRL
/10
V
CTRL
≤
1.0V
T
A
= +25°C
T
A
= +85°C
290
100
0.095
0.100
0.01
0.03
500
170
5
8.2
16.4
50
10.5
21.0
82
780
240
0.105
1
V
µA
kΩ
mV
mV
ms
µS
V
OUT
= 26V, V
CTRL
> 0.24V
V
OUT
= V
IN
, CTRL = GND
(Note 1)
(V
IN
- V
D1
)
10
No switching
CTRL = GND, V
OUT
= V
IN
V
OUT
rising
T
A
= +25°C
T
A
= +85°C
26
V
IN
rising or falling
CONDITIONS
MIN
2.6
2.10
2.38
40
0.38
0.3
1
27
2
20
0.01
30
1
25.5
29
0.55
2
TYP
MAX
5.5
2.55
UNITS
V
V
mV
mA
µA
V
V
µA
V
2
_______________________________________________________________________________________
High-Efficiency, 26V Step-Up Converters
for Two to Six White LEDs
ELECTRICAL CHARACTERISTICS (continued)
(V
IN
= 3V, V
OUT
= 20V, C
OUT
= 0.1µF, C
COMP
= 0.15µF, R
SENSE
= 7.5Ω, V
CTRL
= 1.5V, Figure 1,
T
A
= 0°C to +85°C,
unless other-
wise noted. Typical values are at T
A
= +25°C.)
PARAMETER
N-CHANNEL SWITCH
LX On-Resistance
LX Leakage Current
LX Current Limit
I
LX
= 190mA
V
LX
= 28V, CTRL = GND
Duty cycle = 90%
T
A
= +25°C
T
A
= +85°C
450
1.45
0.01
1
700
950
2.25
5
Ω
µA
mA
CONDITIONS
MIN
TYP
MAX
UNITS
MAX1561/MAX1599
ELECTRICAL CHARACTERISTICS
(V
IN
= 3V, V
OUT
= 20V, C
OUT
= 0.1µF, C
COMP
= 0.15µF, R
SENSE
= 7.5Ω, V
CTRL
= 1.5V, Figure 1,
T
A
= -40°C to +85°C,
unless other-
wise noted.) (Note 3)
PARAMETER
Supply Voltage
UVLO Threshold
Quiescent Current
OVLO Threshold
OUT Input Bias Current
Output Voltage Range
ERROR AMPLIFIER
CTRL to CS Regulation
CTRL Input Resistance
CTRL Dual-Mode Threshold
CTRL Shutdown Enable Delay
CS-to-COMP Transconductance
OSCILLATOR
Operating Frequency
Maximum Duty Cycle
N-CHANNEL SWITCH
LX On-Resistance
LX Current Limit
Duty cycle = 90%
450
2.25
950
Ω
mA
MAX1561
MAX1599
CTRL = IN, CS = GND
0.75
0.37
91
1.25
0.63
MHz
%
(Note 2)
V
COMP
= 1.0V
MAX1561
MAX1599
V
CTRL
= 1V, V
IN
= 2.6V to 5.5V
V
CTRL
≤
1.0V
0.093
240
100
6
13
32
0.107
780
240
11
22
85
V
kΩ
mV
ms
µS
V
IN
rising or falling
No switching
V
OUT
rising
V
OUT
= 26V, V
CTRL
> 0.24V
V
OUT
= V
IN
, CTRL = GND
(Note 1)
(V
IN
- V
D1
)
26
10
CONDITIONS
MIN
2.6
2.10
TYP
MAX
5.5
2.55
0.55
29
30
1
25.5
UNITS
V
V
mA
V
µA
V
Note 1:
V
D1
is the diode forward-voltage drop of diode D1 in Figure 1.
Note 2:
Time from CTRL going below the dual-mode threshold to IC shutdown.
Note 3:
Specifications to -40°C are guaranteed by design and not production tested.
_______________________________________________________________________________________
3
High-Efficiency, 26V Step-Up Converters
for Two to Six White LEDs
MAX1561/MAX1599
Typical Operating Characteristics
(Circuit of Figure 1, V
IN
= 3.6V, I
LED
= 15mA, L1 = 22µH, C
IN
= 2.2µF, C
OUT
= 0.1µF, C
COMP
= 0.1µF, R
SENSE
= 7.5Ω, 4 LEDs,
T
A
= +25°C, unless otherwise noted.)
MAX1561
EFFICIENCY vs. LED CURRENT
(vs. NUMBER of LEDs)
MAX1561 toc01
MAX1561
EFFICIENCY vs. LED CURRENT
(vs. INPUT VOLTAGE)
MAX1561 toc02
MAX1561
EFFICIENCY vs. LED CURRENT
(vs. INDUCTANCE)
MAX1561 toc03
100
90
6 LEDs
EFFICIENCY (%)
80
70
60
50
40
0
5
10
LED CURRENT (mA)
15
100
90
EFFICIENCY (%)
80
70
60
50
40
4.2V
IN
3.6V
IN
100
90
10µH
EFFICIENCY (%)
80
70
60
50
40
47µH
4.7µH
22µH
2.7V
IN
4 LEDs
2 LEDs
20
0
5
10
LED CURRENT (mA)
15
20
0
5
10
LED CURRENT (mA)
15
20
MAX1599 EFFICIENCY vs. LED CURRENT
(vs. NUMBER OF LEDs)
MAX1561 toc04
MAX1599 EFFICIENCY vs. LED CURRENT
(vs. INPUT VOLTAGE)
MAX1561 toc05
MAX1599 EFFICIENCY vs. LED CURRENT
(vs. INDUCTANCE)
47µH
90
EFFICIENCY (%)
80
22µH
70
60
50
40
MAX1561 toc06
100
90
EFFICIENCY (%)
80
70
60
50
40
0
5
10
LED CURRENT (mA)
15
4 LEDs
2 LEDs
6 LEDs
100
90
EFFICIENCY (%)
80
70
60
50
40
100
4.2V
IN
2.7V
IN
3.6V
IN
20
0
5
10
LED CURRENT (mA)
15
20
0
5
10
LED CURRENT (mA)
15
20
INPUT RIPPLE vs. INDUCTANCE
35
INPUT RIPPLE (mV
P-P
)
30
25
20
15
10
5
0
0
5
10 15 20 25 30 35 40 45 50
INDUCTANCE (µH)
1
0
0
1
MAX1561 toc07
INPUT RIPPLE SPECTRUM
MAX1561 toc08
LED CURRENT vs. DIRECT-PWM
DIMMING DUTY CYCLE
MAX1561 toc09
40
6
5
INPUT RIPPLE (mV
RMS
)
4
3
2
25
20
LED CURRENT (mA)
15
10
5
V
CTRL
= SQUARE WAVE
200Hz < FREQ < 200kHz
0
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)
4
_______________________________________________________________________________________
High-Efficiency, 26V Step-Up Converters
for Two to Six White LEDs
MAX1561/MAX1599
Typical Operating Characteristics (continued)
(Circuit of Figure 1, V
IN
= 3.6V, I
LED
= 15mA, L1 = 22µH, C
IN
= 2.2µF, C
OUT
= 0.1µF, C
COMP
= 0.1µF, R
SENSE
= 7.5Ω, 4 LEDs,
T
A
= +25°C, unless otherwise noted.)
SWITCHING WAVEFORMS
MAX1561 toc10
SOFT-START AND SHUTDOWN
MAX1561 toc11
CTRL STEP RESPONSE
MAX1561 toc12
V
IN
10mV/div
V
CTRL
1V/div
0V
V
IN
50mV/div
I
IN
50mA/div
0mA
V
OUT
5V/div
V
IN
= 3.8V Li+ BATTERY
0V
V
IN
= 3.8V Li+ BATTERY
20ms/div
V
CTRL
1V/div
0V
V
IN
50mV/div
I
IN
50mA/div
0mA
V
OUT
5V/div
0V
V
OUT
100mV/div
V
LX
10V/div
500ns/div
20ms/div
DIRECT-PWM DIMMING
MAX1561 toc13
LINE-TRANSIENT RESPONSE
MAX1561 toc14
V
CTRL
32kHz
1V/div
0V
V
IN
50mV/div
I
IN
50mA/div
0mA
V
OUT
5V/div
V
IN
= 3.8V Li+ BATTERY
0V
50µs/div
50µs/div
4V
V
IN
500mV/div
3.5V
I
IN
50mA/div
0mA
V
CS
100mV/div
0V
_______________________________________________________________________________________
5
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