MAX8648ETE+ Datasheet MAX8647ETE+T, MAX8648ETE+T, MAX8647ETE+ | P10-P12

MAX8647/MAX8648

Ultra-Efficient Charge Pumps for

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

10 ______________________________________________________________________________________

Temperature Derating Function

The MAX8647/MAX8648 contain a derating function that

automatically limits the LED current at high temperatures

to help protect the LEDs from damage. The derating

function enables the safe usage of higher LED current at

room temperature, thus reducing the number of LEDs

required to backlight the display. The derating circuit

lowers the LED current at approximately 2.5%/°C once

the IC is above +60°C. The typical derating function

characteristic is shown in the

Typical Operating

Characteristics

Power-Up LED Detection and

Fault Protection

The MAX8648 contains special circuitry to detect short-

circuit conditions at power-up and disable the corre-

sponding current regulator to avoid wasting battery

current. Connect any unused LED_ to IN to disable the

corresponding current regulator. If an LED fails short

circuit, the current regulator continues the current regu-

lated operation until power to the IC is cycled and the

short circuit is detected. An open-circuit LED failure dri-

ves the voltage on the corresponding LED_ output

SDA CONTROL BYTE

COMMAND DATA

FUNCTION

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 0.1mA and off in 32 steps

LED5 current 1 0 1 24.0mA to 0.1mA and off in 32 steps

LED6 current 1 1 0 24.0mA to 0.1mA and off in 32 steps

Not used 1 1 1 —————

Table 2. I

C Control Data Byte—Device Address 0x9A

Note: C2 is MSB and D0 is LSB. The power-on default settings for D4 to D0 are all 0, which indicates that all LED_ are off.

Table 3. MAX8647 I

C Data vs. LED Currents

D4 D3 D2 D1 D0 mA

1111124

1111022.4

1110120.8

1110019.2

1101117.6

1101016

1100114.4

1100012.8

1011111.2

101109.6

101018

101006.4

100115.6

100104.8

100014

100003.2

D4 D3 D2 D1 D0 mA

011112.8

011102.4

011012

011001.6

010111.4

010101.2

010011

010000.8

001110.7

001100.6

001010.5

001000.4

000110.3

000100.2

000010.1

00000OFF

MAX8647/MAX8648

Ultra-Efficient Charge Pumps for

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

______________________________________________________________________________________ 11

below the switch over threshold enabling the inverting

charge pump.

For the MAX8647, program any unused LED_ to off

using the I

C interface. Unused LED_ can be connect-

ed to IN or left unconnected.

Thermal Shutdown

The MAX8647/MAX8648 includes a thermal-limit circuit

that shuts down the IC above about +160°C. The IC

turns on after it cools by approximately 20°C.

Applications Information

Input Ripple

For LED drivers, input ripple is more important than out-

put ripple. The amount of input ripple depends on the

source supply’s output impedance. Adding a lowpass

filter to the input of the MAX8647/MAX8648 further

reduces input ripple. Alternatively, increasing C

2.2µF (or 4.7µF) cuts input ripple in half (or in fourth)

with only a small increase in footprint.

SCL

SDA

SU_STA

HD_STA

BCDEFGHIJKLM

HIGH

LOW

SU_STO

BUF

SU_DAT

HD_DAT

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

J = ACKNOWLEDGE CLOCKED INTO MASTER

K = ACKNOWLEDGE CLOCK PULSE

L = STOP CONDITION, DATA EXECUTED BY SLAVE

M = NEW START CONDITION

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 LOW

Figure 2. Definition of Timing for I

C Bus

Table 4. MAX8648 Pulse Dimming Step vs. LED Currents

mA MAX8648 DIMMING STEPS

24.0 Startup or EN_ high

22.4 1

20.8 2

19.2 3

17.6 4

16.0 5

14.4 6

12.8 7

11.2 8

9.6 9

8.0 10

6.4 11

5.6 12

4.8 13

4.0 14

3.2 15

mA MAX8648 DIMMING STEPS

2.8 16

2.4 17

2.0 18

1.6 19

1.4 20

1.2 21

1.0 22

0.8 23

0.7 24

0.6 25

0.5 26

0.4 27

0.3 28

0.2 29

0.1 30

24.0 31

MAX8647/MAX8648

Ultra-Efficient Charge Pumps for

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

12 ______________________________________________________________________________________

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.

Chip Information

PROCESS: BiCMOS

s TO 500

> 1

INITIAL t

> 120

LED_

0mA0mA

0 12345 262728293031

24mA

22.4

20.8

19.2

17.6

16.0

0.6

0.5

0.4

0.3

0.2

0.1mA

24mA

22.4

SHDN

4ms

Figure 3. EN_ Timing Diagram

Figure 4. MAX8648 Evaluation Kit Layout for C1–C4

P1-P3 P4-P6 P7-P9 P10-P12 P13-P15

MAX8648ETE+

Mfr. #:

Buy MAX8648ETE+

Manufacturer:

Maxim Integrated

Description:

LED Lighting Drivers Charge Pump for 6 White/RGB LEDs

Lifecycle:

New from this manufacturer.

Delivery:

DHL FedEx Ups TNT EMS

Payment:

T/T Paypal Visa MoneyGram Western Union

MAX8648ETE+

MAX8648ETE+

Products related to this Datasheet