19-3117; Rev 0; 12/03
KIT
ATION
EVALU
E
BL
AVAILA
180mA, 1x/2x, White LED Charge Pump
in 3mm x 3mm TDFN
General Description
Features
♦
Up to 180mA (60mA/LED) Drive Capability
♦
83% Average Efficiency (P
LED
/ P
BATT
) Over Li+
Battery Discharge
♦
0.5% (typ) LED Current Matching
♦
Adaptive 1x/2x Mode Switchover
♦
Low Input Ripple and EMI
♦
5% to 100% Dimming Through Single-Wire Serial
Pulse Interface
♦
Low 0.1µA Shutdown Current
♦
2.7V to 5.5V Supply Voltage Range
♦
Soft-Start Limits Inrush Current
♦
Output Overvoltage Protection
♦
Thermal-Shutdown Protection
♦
10-Pin 3mm x 3mm TDFN Package
MAX1574
The MAX1574 charge pump drives up to three white
LEDs with regulated constant current for uniform intensity.
By utilizing adaptive 1x/2x charge-pump modes and
very-low-dropout current regulators, it achieves 180mA
output drive capability and high efficiency over the 1-cell
lithium-battery input voltage range. Fixed-frequency
(1MHz) switching allows for tiny external components,
and the regulation scheme is optimized to ensure low EMI
and low input ripple.
The MAX1574 uses an external resistor to set the full-
scale 100% LED current. An enable input (EN) is used for
simple on/off control or can be pulsed repeatedly to set
lower LED current in multiple steps down to 5%. Once the
desired brightness is set, the MAX1574 maintains con-
stant LED current as long as EN is kept high. If EN is kept
low for more than 2ms, the MAX1574 enters shutdown.
The MAX1574 is available in a 10-pin 3mm x 3mm TDFN
package (0.8mm max height).
Applications
LCD Backlighting
Camera Strobes/Flashes and Movie Lights
Cell Phones/Smart Phones
PDAs, Digital Cameras, and Camcorders
PART
MAX1574ETB
Ordering Information
TEMP RANGE
-40°C to +85°C
PIN-
PACKAGE
10 TDFN
3mm x 3mm
TOP
MARK
ABB
Typical Operating Circuit
0.22µF
GND
OUT
Pin Configuration
LED1
LED2
7
4
CN
TOP VIEW
2.7V TO 5.5V
IN
1µF
CP
CN
OUT
1µF
UP TO 180mA
10
9
8
MAX1574
GND
LED1
ON/OFF AND
DIMMING
EN
MAX1574
LED2
1
IN
2
EN
3
CP
5
SET
SET
LED3
TDFN
3mm
×
3mm
________________________________________________________________
Maxim Integrated Products
LED3
6
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.
180mA, 1x/2x, White LED Charge Pump
in 3mm x 3mm TDFN
MAX1574
ABSOLUTE MAXIMUM RATINGS
IN, OUT, EN to GND..............................................-0.3V to +6.0V
SET, LED1, LED2, LED3, CN to GND .........-0.3V to (VIN + 0.3V)
CP to GND ......................................................................-0.3V to
the greater of (VOUT + 1V) or (VIN + 1V)
OUT Short Circuit to GND ..........................................Continuous
Continuous Power Dissipation (TA = +70°C)
10-Pin TDFN (derate 18.2mW/°C above +70°C) .......1454mW
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
= 3.6V, V
GND
= 0V, EN = IN, R
SET
= 13.7kΩ, T
A
= -40°C to +85°C, unless otherwise noted. Typical values are at T
A
= +25°C.)
(Note 1)
PARAMETER
IN Operating Voltage
Undervoltage-Lockout Threshold
Undervoltage-Lockout Hysteresis
Output Overvoltage-Protection Threshold
No-Load Supply Current
Shutdown Supply Current
Soft-Start Time
SET Bias Voltage
SET Leakage in Shutdown
SET Current Range
SET-to-LED_ Current Ratio (I
LED
/I
SET
)
LED Current Accuracy
LED-to-LED Current Matching
Maximum LED_ Sink Current
LED_ Dropout Voltage
1x to 2x Mode Transition Threshold
Input-Voltage-Mode Transition Hysteresis
LED Leakage in Shutdown
Maximum OUT Current
Open-Loop OUT Resistance
Switching Frequency
OUT Pulldown Resistance in Shutdown
EN High Voltage
EN Low Voltage
EN = GND
V
IN
= 2.7V to 5.5V
V
IN
= 2.7V to 5.5V
1.6
0.4
EN = GND, T
A
= +25°C
EN = GND, T
A
= +85°C
V
IN
≥
3.12V, V
OUT
= 3.9V
1x mode, (V
IN
- V
OUT
) / I
OUT
2x mode, (2 x V
IN
- V
OUT
) / I
OUT
180
1.5
9
1
5
2.5
15
100% setting
T
A
= +25°C
(Note 2)
R
SET
= 4.12kΩ
R
SET
= 4.12kΩ (Note 3)
V
LED_
falling
120
-4
52
EN = GND, T
A
= +25°C
EN = GND, T
A
= +85°C
4
393
±0.7
±0.5
60
80
130
150
0.01
0.1
2
120
140
+4
V
OUT
rising
2x mode
10% setting, 1x mode
EN = GND, T
A
= +25°C
EN = GND, T
A
= +85°C
V
IN
falling
CONDITIONS
MIN
2.7
2.25
2.45
40
5
2
0.35
0.01
0.1
2
0.6
0.01
0.1
153
1
1
TYP
MAX
5.5
2.60
UNITS
V
V
mV
V
mA
µA
ms
V
µA
µA
A/A
%
%
mA
mV
mV
mV
µA
mA
Ω
MHz
kΩ
V
V
2
_______________________________________________________________________________________
180mA, 1x/2x, White LED Charge Pump
in 3mm x 3mm TDFN
ELECTRICAL CHARACTERISTICS (continued)
(V
IN
= 3.6V, V
GND
= 0V, EN = IN, R
SET
= 13.7kΩ, T
A
= -40°C to +85°C, unless otherwise noted. Typical values are at T
A
= +25°C.)
(Note 1)
PARAMETER
EN Input Current
EN Low Shutdown Delay
EN t
LO
(Figure 1)
EN t
HI
(Figure 1)
Initial EN t
HI
(Figure 1)
Thermal-Shutdown Threshold
Thermal-Shutdown Hysteresis
Only required for first EN_ pulse
CONDITIONS
EN = GND or 5.5V, T
A
= +25°C
EN = GND or 5.5V, T
A
= +85°C
1.0
0.5
0.5
50
+160
20
MIN
TYP
0.01
0.1
2
3.3
500
MAX
1
UNITS
µA
ms
µs
µs
µs
°C
°C
MAX1574
Note 1:
Limits are 100% production tested at T
A
= +25°C. Limits over the operating temperature range are guaranteed by design.
Note 2:
LED current matching is defined as: (I
LED
- I
AVG
) / I
AVG
Note 3:
Dropout voltage is defined as the LED_-to-GND voltage at which current into LED_ drops 10% from the value at V
LED_
= 0.2V.
Typical Operating Characteristics
(Circuit of Figure 2, V
IN
= 3.6V, EN = IN, driving three white LEDs, T
A
= +25°C, unless otherwise noted.)
EFFICIENCY vs. INPUT VOLTAGE
MAX1574 toc01
INPUT CURRENT vs. INPUT VOLTAGE
MAX1574 toc02
INPUT RIPPLE vs. SUPPLY VOLTAGE
MAX1574 toc03
100
90
80
EFFICIENCY (%)
70
60
50
40
30
20
10
0
2.7
3.0
3.3
3.6
INPUT VOLTAGE (V)
V
IN
FALLING
3.9
I
LED
= 8mA
I
LED
= 40mA
I
LED
= 20mA
I
LED
= 2mA
300
250
INPUT CURRENT (mA)
200
150
100
50
0
I
LED
= 8mA
I
LED
= 2mA
I
LED
= 40mA
V
IN
FALLING
25
20
INPUT RIPPLE (mV
P-P
)
60mA/LED
15
2mA/LED
10
20mA/LED
8mA/LED
I
LED
= 20mA
5
0
2.7
3.0
3.3
3.6
3.9
4.2
2.5
3.0
3.5
4.0
4.5
5.0
5.5
INPUT VOLTAGE (V)
SUPPLY VOLTAGE (V)
4.2
_______________________________________________________________________________________
3
180mA, 1x/2x, White LED Charge Pump
in 3mm x 3mm TDFN
MAX1574
Typical Operating Characteristics (continued)
(Circuit of Figure 2, V
IN
= 3.6V, EN = IN, driving three white LEDs, T
A
= +25°C, unless otherwise noted.)
LED CURRENT MATCHING
vs. INPUT SUPPLY VOLTAGE
0.8
LED CURRENT MATCHING (%)
0.6
0.4
0.2
0
-0.2
-0.4
-0.6
-0.8
-1.0
2.7
3.1
3.5
3.9
4.3
4.7
7.85
I
LED
= 8mA
5.1
5.5
7.80
-40
-15
10
35
60
85
TEMPERATURE (°C)
1
1
100% BRIGHTNESS
SETTING
10
R
SET
(kΩ)
100
1000
MAX1574 toc04
LED CURRENT vs. TEMPERATURE
MAX1574 toc05
LED CURRENT vs. R
SET
MAX1574 toc06
MAX1574 toc08
1.0
8.20
8.15
8.10
LED CURRENT (mA)
8.05
8.00
7.95
7.90
100
LED CURRENT (mA)
50mV/div
AC-COUPLED
20mV/div
AC-COUPLED
10
INPUT SUPPLY VOLTAGE (V)
OPERATING WAVEFORMS (1x)
MAX1574 toc07
OPERATING WAVEFORMS (2x)
V
OUT
V
OUT
50mV/div
AC-COUPLED
20mV/div
AC-COUPLED
50mA/div
V
IN
V
IN
I
IN
I
IN
50mA/div
0mA
400ns/div
400ns/div
0mA
STARTUP AND SHUTDOWN
MAX1574 toc09
V
EN
5V/div
I
IN
100mA/div
0mA
V
OUT
2V/div
0V
1ms/div
4
_______________________________________________________________________________________
180mA, 1x/2x, White LED Charge Pump
in 3mm x 3mm TDFN
Typical Operating Characteristics (continued)
(Circuit of Figure 2, V
IN
= 3.6V, EN = IN, driving three white LEDs, T
A
= +25°C, unless otherwise noted.)
MAX1574
DIMMING RESPONSE
MAX1574 toc10
LINE TRANSIENT 3.8V TO 3.3V TO 3.8V
MAX1574 toc11
V
IN
V
EN
2V/div
1V/div
V
OUT
I
OUT
50mA/div
1V/div
V
OUT
2V/div
I
OUT
60mA,
20mA/div
10ms/div
100µs/div
Pin Description
PIN
1
NAME
IN
FUNCTION
Supply Voltage Input. Connect a 0.47µF to 1µF ceramic capacitor from IN to GND. The input voltage
range is 2.7V to 5.5V. IN is high impedance during shutdown.
Enable and Dimming Control. Pulsing EN low dims the LEDs in multiple steps. Drive low for longer than
2ms (typ) to shut down the IC. From shutdown, drive EN high (50µs min) to set I
LED
to the maximum
current (see the SETfunction). Pulse EN low for 0.5µs to 500µs to dim the LEDs (Figure 1).
Transfer-Capacitor Positive Connection. Connect a 0.22µF capacitor from CP to CN.
Transfer-Capacitor Negative Connection. Connect a 0.22µF capacitor from CP to CN.
Current-Set Input. Connect a resistor (R
SET
) from SET to GND to set the maximum LED current.
I
LED(MAX)
= 393
×
0.6V / R
SET
. SET is internally biased to 0.6V. SET is high impedance during shutdown.
LED_ Cathode Connection. Current flowing into LED_ is based on SET description above. In 2x mode,
the charge pump regulates the lowest LED_ voltage to 0.18V. Connect LED_ to IN for unpopulated LEDs.
LED_ is high impedance during shutdown.
Ground. Connect GND to system ground and as close as possible to the input-bypass capacitor ground.
Output. Connect a 0.47µF to 1µF ceramic capacitor from OUT to GND, and connect OUT to the anodes
of all the LEDs. OUT is pulled to ground through an internal 5kΩ resistor in shutdown.
Exposed Paddle. Connect the exposed paddle directly to GND underneath the IC.
2
3
4
5
6
7
8
9
10
—
EN
CP
CN
SET
LED3
LED2
LED1
GND
OUT
EP
_______________________________________________________________________________________
5
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