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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

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).

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

Features

♦ Six Adaptive Current Regulators

♦ Independent Voltage Supply for Each LED

♦ Individual LED Brightness Control (MAX8647)

♦ 24mA to 0.1mA Dimming Range

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

Derating Function Protects LEDs

♦ 16-Pin, 3mm x 3mm Thin QFN Package

MAX8647/MAX8648

Ultra-Efficient Charge Pumps for

Six White/RGB LEDs in 3mm x 3mm Thin QFN

________________________________________________________________

Maxim Integrated Products

C1P

C2P

LED4

LED5

LED2

SDA (ENC)

( ) DESIGNATE PINS ON THE MAX8648

12 10 9

SCL (ENB)

(ENA)

LED6

NEG

C1N

C2N

MAX8647ETE

MAX8648ETE

GND LED3

LED1

THIN QFN

TOP VIEW

Pin Configuration

19-0790; Rev 1; 9/07

For pricing, delivery, and ordering information, please contact Maxim Direct at 1-888-629-4642,

or visit Maxim's website at www.maxim-ic.com.

EVALUATION KIT

AVAILABLE

Ordering Information

Note: All devices are specified over the -40°C to +85°C extended

temperature range.

Denotes a lead-free package.

EP = Exposed paddle.

PART DIMMING

PACKAGE

TOP

MARK

PKG

CODE

M A X8 6 4 7 E TE + I

C interface 16 Thi n QFN- E P * AFD T1633- 5

M A X8 6 4 8 E TE +

S eri al -p ul se

l ogi c

16 Thi n QFN- E P * AFE T1633- 5

WHITE

OR RGB LED

LED3

1μF

GND

LED4

LED5

LED6

LED2

MAX8648

LED1

NEG

INPUT

2.7V TO 5.5V

1μF

C1P C1N

1μF

C2P C2N

1μF

SERIAL-

PULSE

INTERFACE

ENA

ENB

ENC

Typical Operating Circuit

Summary of content (15 pages)

PAGE 1
9-0790; Rev 1; 9/07 KIT ATION EVALU E L B AVAILA Ultra-Efficient Charge Pumps for Six White/RGB LEDs in 3mm x 3mm Thin QFN 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 utilizing an inverting charge pump and extremely lowdropout adaptive current regulators, these ICs achieve very high efficiency over the full 1-cell Li+ battery voltage range and even with large LED forward voltage mismatch.
PAGE 2
MAX8647/MAX8648 Ultra-Efficient Charge Pumps for Six White/RGB LEDs in 3mm x 3mm Thin QFN ABSOLUTE MAXIMUM RATINGS VDD, IN, SCL, SDA, ENA, ENB, ENC to GND........-0.3V to +6.0V VDD, 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 (VIN + 0.3V) C2P to C1N .............
PAGE 3
Ultra-Efficient Charge Pumps for Six White/RGB LEDs in 3mm x 3mm Thin QFN (VVDD = VIN = 3.6V, VGND = 0V, TA = -40°C to +85°C, unless otherwise noted. Typical values are at TA = +25°C.) (Note 1) PARAMETER SDA Output Low Voltage CONDITIONS MIN ISDA = 3mA, for acknowledge (Note 2) TYP MAX 0.03 0.40 V 400 kHz I2C Clock Frequency UNITS Bus Free Time Between START and STOP (tBUF) (Note 2) 1.3 Hold Time Repeated START Condition (tHD_STA) (Note 2) 0.6 0.1 µs SCL Low Period (tLOW) (Note 2) 1.
PAGE 4
ELECTRICAL CHARACTERISTICS (continued) (VVDD = VIN = 3.6V, VGND = 0V, TA = -40°C to +85°C, unless otherwise noted. Typical values are at TA = +25°C.) (Note 1) PARAMETER CONDITIONS MIN TYP Derating-Function Start Temperature Derating-Function Slope From derating-function start temperature LED_ RDSON -2.
PAGE 5
Ultra-Efficient Charge Pumps for Six White/RGB LEDs in 3mm x 3mm Thin QFN 20.8mA/LED 50 6.4mA/LED 40 30 20 60 3.0 3.3 3.6 4.2 3.9 80 6.4mA/LED 70 20.8mA/LED 60 50 LEDs HAVE MISMATCHED VF 40 2.7 4.2 3.9 3.8 3.7 LEDs HAVE MISMATCHED VF 40 3.6 4.2 3.9 3.5 3.4 3.0 3.8 3.7 3.6 3.5 3.4 3.0 INPUT VOLTAGE (V) Li+ BATTERY VOLTAGE (V, TIME-WEIGHTED) Li+ BATTERY VOLTAGE (V, TIME-WEIGHTED) INPUT CURRENT vs. INPUT VOLTAGE (DRIVING SIX LEDs) INPUT CURRENT vs.
PAGE 6
Typical Operating Characteristics (continued) (VIN = 3.6V, VEN_ = VIN, circuit of Figure 1, TA = +25°C, unless otherwise noted.) 1x MODE OPERATING WAVEFORMS (VIN = 4V) LED CURRENT vs. TEMPERATURE 1.
PAGE 7
Ultra-Efficient Charge Pumps for Six White/RGB LEDs in 3mm x 3mm Thin QFN PIN NAME FUNCTION 1 IN Supply Voltage Input. The input voltage range is 2.7V to 5.5V. Bypass IN to GND with a 1µF ceramic capacitor as close as possible to the IC. IN is high impedance during shutdown. Connect IN to the anodes of all the LEDs. 2 2 GND Ground. Connect GND to system ground and the input bypass capacitor as close as possible to the IC. 3 3 C1P Transfer Capacitor 1 Positive Connection.
PAGE 8
MAX8647/MAX8648 Ultra-Efficient Charge Pumps for Six White/RGB LEDs in 3mm x 3mm Thin QFN Detailed Description The MAX8647/MAX8648 have an inverting charge pump and six current regulators capable of 24mA each to drive six white LEDs or two sets of RGB LEDs. The current regulators are matched to within ±0.4% (typ) providing uniform white LED brightness for LCD backlight applications. To maximize efficiency, the current regulators operate with as little as 0.15V voltage drop.
PAGE 9
Ultra-Efficient Charge Pumps for Six White/RGB LEDs in 3mm x 3mm Thin QFN VIN 2.7V TO 5.
PAGE 10
MAX8647/MAX8648 Ultra-Efficient Charge Pumps for Six White/RGB LEDs in 3mm x 3mm Thin QFN Table 2. I2C Control Data Byte—Device Address 0x9A SDA CONTROL BYTE COMMAND FUNCTION DATA C2 C1 C0 D4 D3 D2 D1 D0 Not used 0 0 0 — — — — — LED1 current 0 0 1 24.0mA to 0.1mA and off in 32 steps LED2 current 0 1 0 24.0mA to 0.1mA and off in 32 steps LED3 current 0 1 1 24.0mA to 0.1mA and off in 32 steps LED4 current 1 0 0 24.0mA to 0.
PAGE 11
Ultra-Efficient Charge Pumps for Six White/RGB LEDs in 3mm x 3mm Thin QFN tLOW B C tHIGH D E F G H I J K L MAX8647/MAX8648 A M SCL SDA tSU_STA tHD_STA tSU_DAT tHD_DAT tSU_STO F = ACKNOWLEDGE BIT CLOCKED INTO MASTER G = MSB OF DATA CLOCKED INTO SLAVE (OP/SUS BIT) H = LSB OF DATA CLOCKED INTO SLAVE I = SLAVE PULLS SMBDATA LINE LOW A = START CONDITION B = MSB OF ADDRESS CLOCKED INTO SLAVE C = LSB OF ADDRESS CLOCKED INTO SLAVE D = R/W BIT CLOCKED INTO SLAVE E = SLAVE PULLS SMBDATA LINE L
PAGE 12
MAX8647/MAX8648 Ultra-Efficient Charge Pumps for Six White/RGB LEDs in 3mm x 3mm Thin QFN 0 1 2 3 4 5 26 27 28 29 30 31 INITIAL tHI > 120μs EN_ 24mA 22.4 20.8 19.2 tHI > 1μs tLO 1μs TO 500μs 17.6 24mA 22.4 tSHDN 4ms 16.0 ILED_ 0.6 0mA 0.5 0.4 0.3 0.2 0.1mA 0mA Figure 3. EN_ Timing Diagram Capacitor Selection Ceramic capacitors are recommended due to their small size, low cost, and low ESR.
PAGE 13
Ultra-Efficient Charge Pumps for Six White/RGB LEDs in 3mm x 3mm Thin QFN C2P C2N C1P 1μF INPUT 2.7V TO 5.5V NEG GND I2C PORT ON/OFF AND BRIGHTNESS VLOGIC 1.7V TO 5.5V EP GND WHITE OR RGB LED MAX8647 SDA LED2 SCL LED3 SERIALPULSE INTERFACE D4 D5 ENB LED4 ENC LED5 D1 D2 D3 D4 D5 D6 Figure 6. MAX8648 Typical Application Circuit 1μF C1P 1μF C1N C2P C2N 1μF NEG IN EP 1μF GND WHITE OR RGB LED MAX8648 LED1 LED2 SERIALPULSE INTERFACE LED3 LED6 Figure 5.
PAGE 14
Package Information (The package drawing(s) in this data sheet may not reflect the most current specifications. For the latest package outline information, go to www.maxim-ic.com/packages.) (NE - 1) X e E MARKING 12x16L QFN THIN.EPS MAX8647/MAX8648 Ultra-Efficient Charge Pumps for Six White/RGB LEDs in 3mm x 3mm Thin QFN E/2 D2/2 (ND - 1) X e D/2 AAAA e CL D D2 k CL b 0.10 M C A B E2/2 L E2 0.10 C C L 0.08 C C L A A2 A1 L L e e PACKAGE OUTLINE 8, 12, 16L THIN QFN, 3x3x0.
PAGE 15
Ultra-Efficient Charge Pumps for Six White/RGB LEDs in 3mm x 3mm Thin QFN PKG 8L 3x3 12L 3x3 REF. MIN. NOM. MAX. MIN. NOM. MAX. MIN. NOM. MAX. A 0.70 0.75 0.80 0.70 0.75 0.80 0.70 0.75 0.80 b 0.25 0.30 0.35 0.20 0.25 0.30 0.20 0.25 0.30 D 2.90 3.00 3.10 2.90 3.00 3.10 2.90 3.00 3.10 E 2.90 3.00 3.10 2.90 3.00 3.10 2.90 3.00 3.10 e L N 0.55 0.75 0.45 0.55 ND 2 3 NE 2 3 0 A1 A2 k 0.02 0.05 0 0.20 REF 0.25 - 0.65 0.30 12 8 0.02 0.25 - 0.