19-2526; Rev 1; 4/05
White LED Current Regulator with 1x/1.5x
High-Efficiency Charge Pump
General Description
The MAX1570 fractional charge pump drives up to five
white LEDs with regulated constant current for uniform
intensity. The MAX1570 maintains the highest possible
efficiency over the full 1-cell lithium-ion (Li+) battery
input voltage range by utilizing a 1x/1.5x fractional
charge pump and very-low-dropout current regulators.
The MAX1570 operates with 1MHz fixed-frequency
switching, allowing for tiny external components. The
regulation scheme is optimized to ensure low EMI and
low input ripple.
An external resistor sets the full-scale LED current,
while two digital inputs control on/off and select
between three levels of brightness. A pulse-width mod-
ulation (PWM) signal can also be used to modulate LED
brightness.
The MAX1570 is available in 16-pin 4mm
✕
4mm Thin
QFN packaging (0.8mm max height).
♦
30mA/LED Drive Capability
♦
Proprietary 1x/1.5x Modes for Ultra-High
Efficiency
♦
Low Input Ripple and EMI
♦
Eliminates Ballast Resistors
♦
Digital or PWM LED Dimming Control
♦
0.1µA Shutdown Current
♦
2.7V to 5.5V Supply Voltage Range
♦
Soft-Start Limits Inrush Current
♦
Thermal-Shutdown Protection
♦
No External Inductor, Schottky, or Zener Diode
Required
♦
Tiny 16-Pin 4mm
✕
4mm Thin QFN Package
♦2
Features
♦
Excellent 0.3% LED-to-LED Current Matching
MAX1570
Applications
White LED Backlighting
Cell Phones and Smart Phones
PDA and Palmtop Computers
Portable MP3 Players
Digital Cameras and Camcorders
Ordering Information
PART
MAX1570ETE
TEMP RANGE
-40°C to +85°C
PIN-PACKAGE
16 Thin QFN
Pin Configuration
PGND
C1N
EN1
SET
Typical Operating Circuit
1µF
C1P
2.7V TO 5.5V
IN
1µF
1µF
C1N C2P
C2N
OUT
4.7µF
TOP VIEW
12
11
10
9
IN
13
C2P
14
OUT 15
8
7
LED1
LED2
LED3
ON/OFF
AND
DIMMING
EN1
EN2
SET
1x/1.5x
REGULATING CHARGE PUMP
MAX1570
LED1
REFERENCE
AND
CONTROL
LED2
LOW-DROPOUT
CURRENT
REGULATORS
LED3
LED4
LED5
MAX1570
6
5
C2N
16
LED4
1
2
3
4
RSET
GND
PGND
C1P
EN2
GND
THIN QFN
4mm x 4mm
________________________________________________________________
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.
LED5
White LED Current Regulator with 1x/1.5x
High-Efficiency Charge Pump
MAX1570
ABSOLUTE MAXIMUM RATINGS
IN, OUT, EN1, EN2 to GND ......................................-0.3V to +6V
SET, LED1, LED2, LED3, LED4,
LED5 to GND ...........................................-0.3V to (V
IN
+ 0.3V)
PGND to GND..........................................................-0.3 to +0.3V
C1N, C2N to GND ..........................................-0.3V to (V
IN
+ 1V)
C1P, C2P to GND ..........................................-0.3V to the greater
(V
OUT
+ 1V) or (V
IN
+ 1V)
OUT Short Circuit to GND..............................................Indefinite
Continuous Power Dissipation (T
A
= +70°C)
16-Pin Thin QFN (derate 16.9 mW/°C) .......................1349mW
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, GND = PGND = 0, EN1 = EN2 = IN, C
IN
= C1 = C2 = 1µF, C
OUT
= 4.7µF,
T
A
= 0°C to +85°C,
unless otherwise noted.
Typical values are at T
A
= +25°C.)
PARAMETER
IN Operating Voltage
Undervoltage Lockout Threshold
Undervoltage Lockout Hysteresis
Supply Current
Shutdown Supply Current
Soft-Start Done Time
EN1 = GND, EN2 = IN, I
SET
= 33µA
SET Bias Voltage
SET Leakage in Shutdown
SET Current Range
SET to LED_ Current Ratio
LED_ to LED_ Current Matching
Maximum LED_ Sink Current
LED_ Dropout Voltage
I
LED
/I
SET
, I
SET
= 67µA, V
LED_
= 1V
I
SET
= 67µA, V
LED_
= 1V
I
SET
= 130µA, V
LED_
= 1V
I
SET
= 33µA (Note 1)
I
SET
= 67µA (Note 2)
I
SET
= 100µA (Note 2)
LED1 Regulation Voltage
(1.5x Mode)
LED Leakage in Shutdown
Maximum OUT Current
Open-Loop OUT Resistance
Switching Frequency
EN1, EN2 High Voltage
EN1, EN2 Low Voltage
EN1, EN2 Input Current
IN = 2.7V to 5.5V
IN = 2.7V to 5.5V
EN_ = GND or 5.5V
0.01
1.6
0.4
1.00
EN1 = GND, EN2 = IN, I
SET
= 33µA
EN1 = IN, EN2 = GND, I
SET
= 67µA
EN1 = IN, EN2 = IN, I
SET
= 100µA
EN1 = GND, EN2 = GND, V
LED_
= 5.5V
IN
≥
3.4V, OUT
≥
3.9V
1x mode (V
IN
- V
OUT
)/I
OUT
1.5x mode (1.5V
IN
- V
OUT
)/I
OUT
1
150
1.00
1.75
8
185
277
360
EN1 = IN, EN2 = GND, I
SET
= 67µA
EN1 = IN, EN2 = IN, I
SET
= 100µA
EN1 = EN2 = GND, V
IN
= 5.5V, V
SET
= 0 or 5.5V
20
215
-3
28
230
0.3
30
100
200
230
200
300
400
0.01
180
360
410
215
323
440
1.00
µA
mA
Ω
MHz
V
V
µA
mV
mV
0.190
0.380
0.570
1MHz switching, no load
EN1 = EN2 = GND
V
IN
rising or falling
CONDITIONS
MIN
2.7
2.25
2.45
35
2.0
0.1
2.1
0.200
0.400
0.600
0.01
0.210
0.420
0.630
1.00
130
245
+3
µA
µA
A/A
%
mA
V
3.5
5
TYP
MAX
5.5
2.60
UNITS
V
V
mV
mA
µA
ms
2
_______________________________________________________________________________________
White LED Current Regulator with 1x/1.5x
High-Efficiency Charge Pump
ELECTRICAL CHARACTERISTICS (continued)
(V
IN
= 3.6V, GND = PGND = 0, EN1 = EN2 = IN, C
IN
= C1 = C2 = 1µF, C
OUT
= 4.7µF,
T
A
= 0°C to +85°C,
unless otherwise noted.
Typical values are at T
A
= +25°C.)
PARAMETER
LED1 Dual Mode™ Threshold
Thermal-Shutdown Threshold
Thermal-Shutdown Hysteresis
CONDITIONS
MIN
50
TYP
75
160
20
MAX
100
UNITS
mV
°C
°C
MAX1570
ELECTRICAL CHARACTERISTICS
(V
IN
= 3.6V, GND = PGND = 0, EN1 = EN2 = IN, C
IN
= C1 = C2 = 1µF, C
OUT
= 4.7µF,
T
A
= -40°C to +85°C,
unless otherwise noted.)
(Note 3)
PARAMETER
IN Operating Voltage
Undervoltage Lockout Threshold
Supply Current
Shutdown Supply Current
SET Bias Voltage
SET Leakage in Shutdown
SET Current Range
SET to LED_ Current Ratio
LED_ to LED_ Current Matching
Maximum LED_ Sink Current
LED_ Dropout Voltage
I
LED
/I
SET
, I
SET
= 67µA, V
LED_
= 1V
I
SET
= 67µA, V
LED_
= 1V
I
SET
= 130µA, V
LED_
= 1V
I
SET
= 33µA (Note 1)
I
SET
= 67µA (Note 2)
I
SET
= 100µA (Note 2)
LED1 Regulation Voltage
(1.5x Mode)
LED Leakage in Shutdown
Maximum OUT Current
Open-Loop OUT Resistance
EN1, EN2 High Voltage
EN1, EN2 Low Voltage
EN1, EN2 Input Current
LED1 Dual Mode Threshold
EN1 = GND, EN2 = IN, I
SET
= 33µA
EN1 = IN, EN2 = GND, I
SET
= 67µA
EN1 = IN, EN2 = IN, I
SET
= 100µA
EN1 = GND, EN2 = GND, V
LED_
= 5.5V
IN
≥
3.4V, OUT
≥
3.9V
1x mode (V
IN
- V
OUT
)/I
OUT
1.5x mode (1.5V
IN
- V
OUT
)/I
OUT
IN = 2.7V to 5.5V
IN = 2.7V to 5.5V
EN_ = GND or 5.5V
50
1.6
0.4
1
100
150
1.75
8
185
277
360
V
IN
rising or falling
1MHz switching, no load
EN1 = EN2 = GND
EN1 = GND, EN2 = IN, I
SET
= 33µA
EN1 = IN, EN2 = GND, I
SET
= 67µA
EN1 = IN, EN2 = IN, I
SET
= 100µA
EN1 = EN2 = GND, V
IN
= 5.5V, V
SET
= 0 or 5.5V
20
215
-3
28
180
360
410
215
323
440
1
µA
mA
Ω
V
V
µA
mV
mV
mV
0.190
0.380
0.570
CONDITIONS
MIN
2.7
2.25
MAX
5.5
2.60
3.5
5
0.210
0.420
0.630
1
130
250
+3
µA
µA
A/A
%
mA
V
UNITS
V
V
mA
µA
Note 1:
Dropout voltage is defined as the LED_ to GND voltage at which current sink into LED_ drops 20% from the value at LED_ = 1V.
Note 2:
Dropout voltage is defined as the LED_ to GND voltage at which current sink into LED_ drops 10% from the value at LED_ = 1V.
Note 3:
Specifications to -40°C are guaranteed by design and not production tested.
Dual Mode is a trademark of Maxim Integrated Products, Inc.
_______________________________________________________________________________________
3
White LED Current Regulator with 1x/1.5x
High-Efficiency Charge Pump
MAX1570
Typical Operating Characteristics
(EN1 = EN2 = IN, C
IN
= 1µF, C1 = C2 = 1µF, C
OUT
= 4.7µF, R
SET
= 9.09kΩ, T
A
= +25°C, unless otherwise noted.)
LED EFFICIENCY vs. SUPPLY VOLTAGE
(4 LEDs)
MAX1570 toc01
SUPPLY POWER vs. SUPPLY VOLTAGE
(4 LEDs)
350
SUPPLY POWER (mW)
300
250
200
150
100
10mA/LED, EN1 = V
IN
,
EN2 = GND
5mA/LED, EN1 = GND,
EN2 = V
IN
2.5
3.0
3.5
4.0
4.5
5.0
5.5
15mA/LED,
EN1 = EN2 = V
IN
MAX1570 toc02
SUPPLY CURRENT vs. SUPPLY VOLTAGE
(4 LEDs)
90
80
SUPPLY CURRENT (mA)
70
60
50
40
30
20
15mA/LED,
EN1 = EN2 = V
IN
MAX1570 toc03
100
95
EFFICIENCY P
LED
/P
SUPPLY
(%)
90
85
80
75
70
65
60
55
50
5mA/LED, EN1 = GND,
EN2 = V
IN
3.0
3.2
3.4
3.6
15mA/LED,
EN1 = EN2 = V
IN
3.8
4.0
10mA/LED, EN1 = V
IN
, EN2 = GND
400
100
10mA/LED, EN1 = V
IN
,
EN2 = GND
5mA/LED, EN1 = GND,
EN2 = V
IN
50
0
10
0
2.5
3.0
3.5
4.0
4.5
SUPPLY VOLTAGE (V)
5.0
4.2
SUPPLY VOLTAGE (V)
SUPPLY VOLTAGE (V)
LED EFFICIENCY vs. SUPPLY VOLTAGE
(5 LEDs)
MAX1570 toc04
SUPPLY POWER vs. SUPPLY VOLTAGE
(5 LEDs)
MAX1570 toc05
SUPPLY CURRENT vs. SUPPLY VOLTAGE
(5 LEDs)
MAX1570 toc06
100
95
EFFICIENCY P
LED
/P
SUPPLY
(%)
90
85
80
75
70
65
60
55
50
5mA/LED, EN1 = GND,
EN2 = V
IN
3.0
3.2
3.4
3.6
15mA/LED,
EN1 = EN2 = V
IN
3.8
4.0
10mA/LED, EN1 = V
IN
, EN2 = GND
500
450
400
SUPPLY POWER (mW)
350
300
250
200
150
100
50
0
2.5
3.0
5mA/LED, EN1 = GND,
EN2 = V
IN
3.5
4.0
4.5
SUPPLY VOLTAGE (V)
10mA/LED, EN1 = V
IN
,
EN2 = GND
15mA/LED,
EN1 = EN2 = V
IN
120
100
SUPPLY CURRENT (mA)
80
60
40
20
0
10mA/LED, EN1 = V
IN
,
EN2 = GND
5mA/LED, EN1 = GND,
EN2 = V
IN
15mA/LED,
EN1 = EN2 = V
IN
4.2
5.0
2.5
3.0
SUPPLY VOLTAGE (V)
3.5
4.0
4.5
SUPPLY VOLTAGE (V)
5.0
EFFICIENCY vs. LED CURRENT
(4 LEDs, EN1 = PWM AT 1kHz)
MAX1570 toc07
LED CURRENT vs. PWM DIMMING
DUTY CYCLE INTO EN1 (5 LEDs)
MAX1570 toc08
SUPPLY CURRENT vs. SUPPLY VOLTAGE
(4 LEDs, LED1 OPEN FOR 1.5X ONLY MODE)
MAX1570 toc09
100
95
EFFICIENCY P
LED
/P
SUPPLY
(%)
90
85
80
75
70
65
60
55
50
5
6
7
8
9
V
IN
= 3V
V
IN
= 3.9V
20
18
16
LED CURRENT (mA)
14
12
10
8
6
4
2
0
f
PWM
= 1kHz
V
IN
= 3.3V
120
100
SUPPLY CURRENT (mA)
80
60
40
20
0
5mA/LED, EN1 = GND,
EN2 = V
IN
15mA/LED,
EN1 = EN2 = V
IN
10mA/LED, EN1 = V
IN
,
EN2 = GND
10 11 12 13 14 15
0
10 20 30 40 50 60 70 80 90 100
PWM DUTY CYCLE (%)
2.5
3.0
LED CURRENT (mA)
3.5
4.0
4.5
SUPPLY VOLTAGE (V)
5.0
4
_______________________________________________________________________________________
White LED Current Regulator with 1x/1.5x
High-Efficiency Charge Pump
MAX1570
Typical Operating Characteristics (continued)
(EN1 = EN2 = IN, C
IN
= 1µF, C1 = C2 = 1µF, C
OUT
= 4.7µF, R
SET
= 9.09kΩ, T
A
= +25°C, unless otherwise noted.)
LED CURRENT vs. TEMPERATURE
(V
IN
= 3.3V, R
SET
= 7.5kΩ)
MAX1570 toc11
MAX1570 toc10
LED CURRENT vs. SUPPLY VOLTAGE
20
18
16
LED CURRENT (mA)
14
12
10
8
6
4
2
0
2.5
3.0
3.5
4.0
4.5
5.0
5.5
SUPPLY VOLTAGE (V)
EN1 = GND, EN2 = V
IN
EN1 = V
IN
, EN2 = GND
EN1 = EN2 = V
IN
LED CURRENT (mA)
12.0
11.9
11.8
11.7
11.6
11.5
11.4
11.3
11.2
11.1
11.0
-40
LED CURRENT vs. R
SET
MAX1570 toc12
30
25
LED CURRENT (mA)
20
15
EN1
E
N1
=
EN
10
EN1
=
=
IN
2=I
N
,
EN2
=
GND
EN1 = IN
EN2 = GND
-15
10
35
TEMPERATURE (°C)
60
85
5
0
5.0
7.5
GN
D,
E
N
2
=
IN
10.0
R
SET
(kΩ)
12.5
15.0
TYPICAL OPERATING WAVEFORM
IN 1X MODE
MAX1570 toc13
TYPICAL OPERATING WAVEFORM
IN 1.5X MODE (I
LOAD
= 90mA, V
IN
= 3.6V)
MAX1570 toc14
STARTUP RESPONSE (V
IN
= 3.3V)
(5 LEDs AT 15mA/LED)
MAX1570 toc15
I
IN
AC-COUPLED
10mA/div
V
IN
AC-COUPLED
1mV/div
V
OUT
AC-COUPLED
1mV/div
I
IN
AC-COUPLED
10mA/div
V
IN
AC-COUPLED
20mV/div
V
OUT
AC-COUPLED
5mV/div
I
IN
50mA/div
V
OUT
2V/div
2µs/div
400ns/div
400µs/div
DIMMING RESPONSE USING
PWM INTO EN1
MAX1570 toc16
LINE-TRANSIENT RESPONSE
MAX1570 toc17
I
LED
15mA TO 5mA
5mA/div
I
LED
15mA
5mA/div
V
OUT
AC-COUPLED
500mV/div
EN1
0 TO 2V
2V/div
100µs/div
100µs/div
V
OUT
AC-COUPLED
500mV/div
V
IN
4 TO 3.6V
500mV/div
_______________________________________________________________________________________
5
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