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MAX8647ETE

Ultra-Efficient Charge Pumps for Six White/RGB LEDs in 3mm x 3mm Thin QFN

Maxim Integrated 

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

EN_

INITIAL tHI

> 120μs

ILED_

0mA

tLO

24mA

22.4 20.8 19.2 17.6

1μs TO 500μs

16.0

tHI

> 1μs

24mA 22.4

tSHDN

4ms

0.6 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. Select ceramic capacitors

that maintain their capacitance over temperature and

DC bias. Capacitors with X5R or X7R temperature char-

acteristics generally perform well. Recommended val-

ues are shown in the Typical Operating Circuit. Using a

larger value input capacitor helps to reduce input ripple

(see the Input Ripple section).

Driving LEDs with Multiple Supplies

It is not necessary for the LED anodes to connect to IN.

Figure 7 shows an example using separate supplies to

power the LED_ groups of the MAX8648. In this exam-

ple, the voltage source (V1) provides power for RGB

LEDs (LED1, LED2, and LED3). V2 provides power for

backlight LEDs (LED4 and LED5), and V3 provides

power for a red charge indicator (LED6).

PCB Layout and Routing

The MAX8647/MAX8648 have a high-frequency,

switched-capacitor voltage inverter. For best circuit per-

formance, use a solid copper plane and place C1–C4 as

close as possible to the MAX8647/MAX8648. Figure 4

shows the MAX8648 evaluation kit example layout.

Figure 4. MAX8648 Evaluation Kit Layout for C1–C4

PROCESS: BiCMOS

Chip Information

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