19-0790; Rev 0; 4/07
Ultra-Efficient Charge Pumps for
Six White/RGB LEDs in 3mm x 3mm Thin QFN
General Description
The MAX8647/MAX8648 drive up to six white LEDs or
two sets of RGB LEDs with regulated constant current
for display backlight and fun light applications. By utiliz-
ing an inverting charge pump and extremely low-
dropout adaptive current regulators, these ICs achieve
very high efficiency over the full 1-cell Li+ battery volt-
age range and even with large LED forward voltage
mismatch. The 1MHz fixed-frequency switching allows
for tiny external components. The regulation scheme is
optimized to ensure low EMI and low input ripple. The
MAX8647/MAX8648 include thermal shutdown, open-
and short-circuit protection.
The MAX8647 features an I
2
C serial port, while the
MAX8648 features a three-wire serial-pulse logic inter-
face. Both devices support independent on/off and
dimming for main and subbacklights. The dimming
ranges are pseudo-logarithmic from 24mA to 0.1mA
and off in 32 steps. Both devices include a temperature
derating function to safely allow bright 24mA full-scale
output current setting while automatically reducing cur-
rent to protect LEDs at high ambient temperatures
above +60°C.
The MAX8647/MAX8648 are available in a 16-pin, 3mm
x 3mm thin QFN package (0.8mm max height).
♦
♦
♦
♦
♦
♦
♦
♦
♦
♦
KIT
ATION
EVALU
BLE
AVAILA
Features
Six Adaptive Current Regulators
Independent Voltage Supply for Each LED
Individual LED Brightness Control (MAX8647)
24mA to 0.1mA Dimming Range
I
2
C Interface (MAX8647)
Serial-Pulse Dimming Logic (MAX8648)
±2% Accuracy, ±0.4% Matching (typ)
Low 70µA Quiescent Current
Low 1µA Shutdown Current
Inrush Current Limit
T
A
Derating Function Protects LEDs
16-Pin, 3mm x 3mm Thin QFN Package
MAX8647/MAX8648
Ordering Information
PART
DIMMING
PIN
PACKAGE
TOP
MARK
AFD
AFE
PKG
CODE
T1633-5
T1633-5
MAX8647
ETE+ I
2
C interface 16 Thin QFN-EP*
MAX8648
ETE+
Serial-pulse
16 Thin QFN-EP*
logic
Applications
White LED Backlighting, Single or Dual Display
Wide-Gamut RGB LED Display Backlighting
Camera Flash or RGB Indicators
Cellular Phones and Smartphones
PDAs, Digital Cameras, and Camcorders
Note:
All devices are specified over the -40°C to +85°C extended
temperature range.
+Denotes
a lead-free package.
*EP
= Exposed paddle.
Typical Operating Circuit
1μF
1μF
Pin Configuration
LED2
LED4
LED3
LED5
C1P
INPUT
2.7V TO 5.5V
1μF
GND
C1N
C2P
C2N
NEG
1μF
TOP VIEW
IN
EP
WHITE
OR RGB LED
12
LED1 13
SDA (ENC) 14
SCL (ENB) 15
V
DD
(ENA) 16
11
10
9
8
7
LED6
NEG
C1N
C2N
MAX8648
LED1
LED2
D1
D2
D3
D4
D5
D6
MAX8647ETE
MAX8648ETE
+
1
IN
2
GND
3
C1P
4
C2P
6
5
ENA
SERIAL-
PULSE
INTERFACE
ENB
ENC
LED3
LED4
LED5
LED6
THIN QFN
( ) DESIGNATE PINS ON THE MAX8648
________________________________________________________________
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.
Ultra-Efficient Charge Pumps for
Six White/RGB LEDs in 3mm x 3mm Thin QFN
MAX8647/MAX8648
ABSOLUTE MAXIMUM RATINGS
V
DD
, IN, SCL, SDA, ENA, ENB, ENC to GND........-0.3V to +6.0V
V
DD
, IN, SCL, SDA, ENA, ENB, ENC to NEG ........-0.3V to +6.0V
NEG to GND .............................................................-6V to +0.3V
C2N to GND .............................................................-6V to +0.3V
C1P, C2P to GND .......................................-0.3V to (V
IN
+ 0.3V)
C2P to C1N ..................................................-0.3V to (V
IN
+ 0.3V)
LED_, C1N, C2N to NEG .............................-0.3V to (V
IN
+ 0.3V)
Continuous Power Dissipation (T
A
= +70°C)
16-Pin Thin QFN 3mm x 3mm (derate 20.8mW/°C
above +70°C).............................................................1667mW
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
VDD
= V
IN
= 3.6V, V
GND
= 0V, T
A
= -40°C to +85°C, unless otherwise noted. Typical values are at T
A
= +25°C.) (Note 1)
PARAMETER
IN Operating Voltage
V
DD
Operating Voltage
Undervoltage-Lockout (UVLO)
Threshold
Undervoltage-Lockout Hysteresis
IN Shutdown Supply Current
(All Outputs Off)
V
DD
Shutdown Supply Current
V
SCL
= V
SDA
= V
DD
(MAX8647),
V
EN
_ = 0V (MAX8648)
T
A
= +25°C
T
A
= +85°C
Charge pump inactive, two LEDs enabled at 0.1mA
setting
IN Operating Supply Current
Charge pump active, 1MHz switching, all LEDs
enabled at 0.1mA setting
Charge pump inactive, two LEDs enabled at 0.1mA
setting, T
A
= +25°C
Charge pump active, 1MHz switching, all LEDs
enabled at 0.1mA setting, T
A
= +85°C
T
A
= +25°C
T
A
= +85°C
V
IN
rising
CONDITIONS
MIN
2.7
1.7
2.35
2.45
100
0.4
0.4
0.1
0.1
70
1.6
0.1
0.1
+160
20
0.7 x
V
DD
0.3 x
V
DD
50
-1
0.01
0.1
+1
°C
°C
1.0
µA
100
1.0
2.5
TYP
MAX
5.5
5.5
2.55
UNITS
V
V
V
mV
µA
µA
µA
mA
V
DD
Operating Supply Current
Thermal-Shutdown Threshold
Thermal-Shutdown Hysteresis
I
2
C INTERFACE (MAX8647)
Logic-Input High Voltage (SDA, SCL)
Logic-Input Low Voltage (SDA, SCL)
Filtered Pulse Width (t
SP
)
Logic-Input Current (SDA, SCL)
V
DD
= 1.7V to 5.5V, hysteresis = 0.2 x V
DD
(typ)
V
DD
= 1.7V to 5.5V, hysteresis = 0.2 x V
DD
(typ)
V
IN
= 2.7V to 5.5V, V
DD
= 1.7V to 5.5V (Note 2)
V
IL
= 0V or V
IH
= 5.5V
T
A
= +25°C
T
A
= +85°C
V
V
ns
µA
2
_______________________________________________________________________________________
Ultra-Efficient Charge Pumps for
Six White/RGB LEDs in 3mm x 3mm Thin QFN
ELECTRICAL CHARACTERISTICS (continued)
(V
VDD
= V
IN
= 3.6V, V
GND
= 0V, T
A
= -40°C to +85°C, unless otherwise noted. Typical values are at T
A
= +25°C.) (Note 1)
PARAMETER
SDA Output Low Voltage
I
2
C Clock Frequency
Bus Free Time Between START and
STOP (t
BUF
)
Hold Time Repeated START Condition
(t
HD_STA
)
SCL Low Period (t
LOW
)
SCL High Period (t
HIGH
)
Setup Time Repeated START
Condition (t
SU_STA
)
SDA Hold Time (t
HD_DAT
)
SDA Setup Time (t
SU_DAT
)
Setup Time for STOP Condition
(t
SU_STO
)
Logic-Input High Voltage
Logic-Input Low Voltage
Logic-nput Current
t
SHDN
(Figure 3)
t
LO
(Figure 3)
t
HI
(Figure 3)
Initial t
HI
(Figure 3)
CHARGE PUMP
Switching Frequency
Soft-Start Time
Charge-Pump Regulation Voltage
Open-Loop NEG Output Resistance
NEG Discharge Resistance in
Shutdown or When the Charge Pump
is Inactive
LED1–LED6 CURRENT REGULATOR
Current Setting Range
Through an I
2
C or serial-pulse interface
V
LED_
= 0.5V for
charge-pump inactive,
V
LED_
= -0.9V,
V
NEG_
= -1.4V
24mA setting, T
A
= +25°C
24mA setting, T
A
= -40°C
to derating function start
temperature (Note 2)
1.6mA setting, T
A
= +25°C
0.1
-2
-5
-15
±5
±1
24.0
+2
+5
+15
%
mA
(V
IN
- V
NEG
)
(V
NEG
- 0.5 x V
IN
) / I
NEG
All LEDs off, EN_ = GND
4.3
1
0.5
5.0
2.5
10
5
MHz
ms
V
Ω
kΩ
First EN_ high pulse
(Note 2)
(Note 2)
(Note 2)
(Note 2)
(Note 2)
(Note 2)
(Note 2)
(Note 2)
1.3
0.6
1.3
0.6
0.6
0
100
0.6
0.1
0.2
0.2
0.1
-0.01
50
0.1
CONDITIONS
I
SDA
= 3mA, for acknowledge (Note 2)
MIN
TYP
0.03
MAX
0.40
400
UNITS
V
kHz
µs
µs
µs
µs
µs
µs
ns
µs
MAX8647/MAX8648
SERIAL-PULSE LOGIC (EN_) (MAX8648)
V
IN
= 2.7V to 5.5V
V
IN
= 2.7V to 5.5V
V
IL
= 0V or V
IH
= 5.5V
T
A
= +25°C
T
A
= +85°C
1
1
120
-1
0.01
0.1
4
500
1.4
0.4
+1
V
V
µA
ms
µs
µs
µs
Time from EN_ held low to I
LED_
= 0mA
Current Accuracy
_______________________________________________________________________________________
3
Ultra-Efficient Charge Pumps for
Six White/RGB LEDs in 3mm x 3mm Thin QFN
MAX8647/MAX8648
ELECTRICAL CHARACTERISTICS (continued)
(V
VDD
= V
IN
= 3.6V, V
GND
= 0V, T
A
= -40°C to +85°C, unless otherwise noted. Typical values are at T
A
= +25°C.) (Note 1)
PARAMETER
Derating-Function Start Temperature
Derating-Function Slope
LED_ R
DSON
LED_ Dropout
LED_ Current Regulator Switchover
Threshold (Inactive to Active)
LED_ Current Regulator Switchover
Hysteresis
LED_ Leakage in Shutdown
All LEDs off
T
A
= +25°C
T
A
= +85°C
From derating-function start temperature
Not utilizing the charge pump
Utilizing the charge pump
24mA setting
(Note 3)
V
LED_
falling
Not utilizing the charge pump
Utilizing the charge pump
125
CONDITIONS
MIN
TYP
+60
-2.5
3
4
60
90
150
100
0.01
0.1
5
120
200
175
MAX
UNITS
°C
%/°C
Ω
mV
mV
mV
µA
Note 1:
Limits are 100% production tested at T
A
= +25°C. Specifications over the operating temperature range are guaranteed by design.
Note 2:
Guaranteed by design.
Note 3:
LED dropout voltage is defined as the LED_ to GND voltage at which current into LED_ drops 10% from the value at V
LED_
= 0.5V.
Typical Operating Characteristics
(V
IN
= 3.6V, V
EN_
= V
IN
, circuit of Figure 1, T
A
= +25°C, unless otherwise noted.)
EFFICIENCY vs. SUPPLY VOLTAGE
(DRIVING SIX MATCHED LEDs)
MAX8647/48 toc01
EFFICIENCY vs. Li+ BATTERY VOLTAGE
(DRIVING SIX MATCHED LEDs)
MAX8647/48 toc02
EFFICIENCY vs. SUPPLY VOLTAGE
(DRIVING SIX LEDs)
90
80
EFFICIENCY (%)
70
60
50
40
30
20
10
LEDs HAVE MISMATCHED V
F
2.7
3.0
3.3
3.6
3.9
4.2
16mA/LED
1.6mA/LED
MAX8647/48 toc03
100
90
80
EFFICIENCY (%)
70
60
50
40
30
20
10
0
2.7
3.0
3.3
3.6
3.9
1.6mA/LED
20.8mA/LED
16mA/LED
6.4mA/LED
100
90
EFFICIENCY P
LED
/P
BATT
(%)
80
70
1.6mA/LED
60
50
40
16mA/LED
6.4mA/LED
20.8mA/LED
100
0
4.2 3.9
3.8
3.7
3.6
3.5 3.4 3.0
Li+ BATTERY VOLTAGE (V, TIME-WEIGHTED)
4.2
INPUT VOLTAGE (V)
INPUT VOLTAGE (V)
4
_______________________________________________________________________________________
Ultra-Efficient Charge Pumps for
Six White/RGB LEDs in 3mm x 3mm Thin QFN
Typical Operating Characteristics (continued)
(V
IN
= 3.6V, V
EN_
= V
IN
, circuit of Figure 1, T
A
= +25°C, unless otherwise noted.)
EFFICIENCY vs. SUPPLY VOLTAGE
(DRIVING SIX LEDs)
MAX8647/48 toc04
MAX8647/MAX8648
EFFICIENCY vs. Li+ BATTERY VOLTAGE
(DRIVING SIX LEDs)
16mA/LED
90
EFFICIENCY P
LED
/P
BATT
(%)
80
70
1.6mA/LED
60
50
MAX8647/48 toc05
EFFICIENCY vs. Li+ BATTERY VOLTAGE
(DRIVING SIX LEDs)
MAX8647/48 toc06
100
90
80
EFFICIENCY (%)
70
60
50
40
30
20
10
0
2.7
LEDs HAVE MISMATCHED V
F
6.4mA/LED
20.8mA/LED
100
100
90
EFFICIENCY P
LED
/P
BATT
(%)
80
6.4mA/LED
70
60
50
20.8mA/LED
40
3.0
3.3
3.6
3.9
4.2
INPUT VOLTAGE (V)
LEDs HAVE MISMATCHED V
F
4.2 3.9
3.8
3.7
3.6
3.5 3.4 3.0
40
LEDs HAVE MISMATCHED V
F
4.2 3.9
3.8
3.7
3.6
3.5 3.4 3.0
Li+ BATTERY VOLTAGE (V, TIME-WEIGHTED)
Li+ BATTERY VOLTAGE (V, TIME-WEIGHTED)
INPUT CURRENT vs. INPUT VOLTAGE
(DRIVING SIX LEDs)
MAX8647/48 toc07
INPUT CURRENT vs. Li+ BATTERY
VOLTAGE (DRIVING SIX LEDs)
MAX8647/48 toc08
INPUT CURRENT
vs. INPUT VOLTAGE (RGB MODULE)
RGB MODULE: LUMEX SML-LX3632SISUGSBC
I
LED
= 20.8mA
I
LED
= 16mA
90
80
INPUT CURRENT (mA)
70
60
50
40
30
20
10
0
I
LED
= 1.6mA
I
LED
= 4.8mA
MAX8647/48 toc09
MAX8647/48 toc12
200
180
160
INPUT CURRENT (mA)
140
120
100
80
60
40
20
0
2.7
3.2
3.7
I
LED
= 1.6mA
I
LED
= 16mA
LEDs HAVE MISMATCHED V
F
I
LED
= 6.4mA
I
LED
= 20.8mA
200
180
160
INPUT CURRENT (mA)
140
120
100
80
60
40
20
0
LEDs HAVE MISMATCHED V
F
100
20.8mA/LED
16mA/LED
6.4mA/LED
1.6mA/LED
4.2 3.9
3.8
3.7
3.6
3.5 3.4 3.0
4.2
2.7
3.2
3.7
4.2
INPUT VOLTAGE (V)
Li+ BATTERY VOLTAGE (V, TIME-WEIGHTED)
INPUT VOLTAGE (V)
INPUT CURRENT vs. Li+ BATTERY
VOLTAGE (RGB MODULE)
MAX8647/48 toc10
INPUT RIPPLE VOLTAGE vs. SUPPLY
VOLTAGE (DRIVING SIX WHITE LEDs)
14
12
10
8
6.4mA/LED
6
4
2
0
1.6mA/LED
2.7
3.2
3.7
4.2
LEDs HAVE
MISMATCHED V
F
20.8mA/LED
16mA/LED
MAX8647/48 toc11
LED CURRENT MATCHING
vs. INPUT VOLTAGE (16mA/LED)
17.0
16.8
16.6
LED CURRENT (mA)
16.4
16.2
16.0
15.8
15.6
15.4
15.2
15.0
2.7
3.1
3.5
3.9
4.3
4.7
5.1
5.5
100
90
80
INPUT CURRENT (mA)
70
60
50
40
30
20
10
0
RGB MODULE: LUMEX SML-LX3632SISUGSBC
20.8mA/LED
16mA/LED
16
INPUT RIPPLE VOLTAGE (mV
RMS
)
6.4mA/LED
1.6mA/LED
4.2 3.9
3.8
3.7
3.6
3.5 3.4 3.0
Li+ BATTERY VOLTAGE (V, TIME-WEIGHTED)
SUPPLY VOLTAGE (V)
INPUT VOLTAGE (V)
_______________________________________________________________________________________
5
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