Maxim MAX8678, MAX8678ETE+ Datasheet

General Description

The MAX8678 integrates a charge pump for white light­emitting diodes (LEDs) with an audio loudspeaker
amplifier. The high-efficiency, adaptive charge pump
drives up to four LEDs with constant current for uniform
brightness. The LED current is adjustable from

0.1mA/LED to 24mA/LED in 31 pseudo-logarithmic
steps through a single-wire serial-pulse interface. High
accuracy and LED-to-LED current matching are main­tained throughout the adjustment range. Individual
adaptive mode switching for each LED provides high
efficiency with a wide range of LED forward voltages.

The mono class AB audio amplifier directly drives an 8Ω
loudspeaker with 1.1W RMS continuous power from a 5V
supply with less than 1% THD+N. The gain is adjustable
from -9dB to +18dB in ten 3dB steps through a single­wire serial-pulse interface. Clicks and pops are sup­pressed during on/off and all gain adjustments.
Differential inputs improve common-mode noise rejection.

The MAX8678 includes soft-start, thermal shutdown,
open-circuit and short-circuit protection, and is avail­able in the 16-pin, 3mm x 3mm Thin QFN package
(0.8mm max height).

Applications

Cell Phones and Smartphones

Camera Phones

PDAs, Digital Cameras, Camcorders

Features

♦ High-Efficiency White LED Charge Pump

Individual Adaptive Supply for Each LED
4 Low-Dropout LED Current Regulators
24mA to 0.1mA Dimming Range
Single-Wire, Serial-Pulse Dimming Interface
1% (typ) Accuracy
Low 140µA Quiescent Current

♦ Mono Class AB Audio Amplifier

1.1W RMS Mono BTL Output (8Ω, VIN= 5V)
Low 0.004% THD+N at 1kHz
High 90dB PSRR at 1kHz
Fully Differential Inputs

-9dB to +18dB Gain Settings in 3dB Steps
Integrated Click/Pop Suppression
Low Quiescent Current

♦ Soft-Start Limits Inrush Current

♦ Thermal Shutdown, Open- and Short-Circuit

Protection

♦ 16-Pin, 3mm x 3mm Thin QFN Package

MAX8678

White LED Charge Pump with

1.1W Audio Amplifier

________________________________________________________________

Maxim Integrated Products

1

15

16

14

13

6

5

7

GND

A-

8

IN

LED3

LED1

LED4

12

C-

4

12 11 9

C+

+

ENLED

BIAS

OUT-

OUT+

ENAMP

MAX8678

A+ LED2

3

10

NEG

THIN QFN

3mm × 3mm

TOP VIEW

Pin Configuration

Ordering Information

MAX8678

C+

INPUT

2.7V TO 5.5V

LED ON/OFF

AND DIMMING

AMP ON/OFF

AND GAIN

DIFFERENTIAL

AUDIO

INPUT

C-

LED1

LED2

LED3

IN

BACKLIGHT
OR FLASH

0.1mA TO
24mA

LOUDSPEAKER
8Ω

GND

ENLED

LED4

BIAS

OUT+

OUT-

NEGEP

0.1μF

1μF

1μF

4.7μF

ENAMP

A+

A-

Typical Operating Circuit

19-0786; Rev 0; 4/07

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.

PART

PIN-PACKAGE TOP MARK

PKG CODE

MAX8678ETE+

16 Thin QFN
3mm x 3mm

AFF T1633-5

+

Denotes a lead-free package.

Note: The device is specified over the -40°C to +85°C extend­ed temperature range.

MAX8678

White LED Charge Pump with

1.1W Audio Amplifier

2 _______________________________________________________________________________________

ABSOLUTE MAXIMUM RATINGS

ELECTRICAL CHARACTERISTICS

(VIN= 3.6V, V

GND

= 0V, TA= -40°C to +85°C, unless otherwise noted. Typical values are at TA= +25°C.) (Note 1)

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.

IN to GND ..............................................................-0.3V to +6.0V

IN to NEG ..............................................................-0.3V to +6.0V

ENLED, ENAMP, LED_, C+, A+, A-, OUT+, OUT-,

BIAS to GND…….....................................-0.3V to (V

IN

+ 0.3V)

ENLED, ENAMP, LED_, C+, A+, A-, OUT+, OUT-,

BIAS, C- to NEG...................................…-0.3V to (V

IN

+ 0.3V)

GND to NEG ......................................................…-0.3V to +6.0V

GND to C-..............................................................-0.3V to +6.0V

OUT+, OUT- Short Circuit to GND or IN ....................Continuous

Continuous Power Dissipation (T

A

= +70°C)
16-Pin Thin QFN 3mm x 3mm

(derate 17.5mW/°C above +70°C)............................1398mW

Junction Temperature......................................................+150°C

Storage Temperature Range .............................-65°C to +150°C

Lead Temperature (soldering, 10s) .................................+300°C

PARAMETER CONDITIONS MIN TYP MAX UNITS

IN Operating Voltage 2.7 5.5 V

Undervoltage-Lockout (UVLO) Threshold VIN rising 2.25 2.45 2.65 V

UVLO Hysteresis 100 mV

TA = +25°C 0.1 1.5

Shutdown Supply Current
(All Outputs Off)

ENLED = ENAMP =
GND

T

A

= +85°C 0.1

µA

Charge pump inactive, LED_ = 1.6mA
ENAMP = GND, T

A

= +25°C

140 200 µA

Charge pump active, 1MHz switching, LEDs at
24mA setting, ENAMP = GND

0.45

No-Load Supply Current

ENAMP = IN, ENLED = GND 3

mA

Thermal Shutdown +160 °C

Thermal-Shutdown Hysteresis 20 °C

SERIAL-PULSE INTERFACE (EN_)

VIN = 2.7V to 4.2V 1.4

Logic Input-High Voltage

V

IN

= 4.2V to 5.5V 1.5

V

Logic Input-Low Voltage VIN = 2.7V to 5.5V 0.4 V

TA = +25°C 0.01 1

Logic Input Current

V

IL

= 0V or

V

IH

= 5.5V

T

A

= +85°C 0.1

µA

t

SHDN

See Figures 2 and 3 3.2 ms

t

HOLD

See Figures 2 and 3 3.2 ms

t

LO

See Figures 2 and 3 0.5 500 µs

t

HI

See Figures 2 and 3 0.5 500 µs

CHARGE PUMP

Switching Frequency 1 MHz

Soft-Start Time 0.1 ms

Regulation Voltage (OVP) (VIN - V

NEG

)5V

Open-Loop NEG Output Resistance
((V

NEG

-VIN)/I

NEG

)

10 23 Ω

Guaranteed Output Current LED VF = 3.9V, VIN = 3.2V 96 mA

NEG Discharge Resistance in Shutdown All LEDs off, ENLED = GND 10 kΩ

MAX8678

White LED Charge Pump with

1.1W Audio Amplifier

_______________________________________________________________________________________ 3

Note 1: Limits are 100% production tested at TA= +25°C. Limits over the operating temperature range are guaranteed by design.
Note 2: Dropout voltage is defined as the LED_ to GND (charge pump inactive) or LED_ to NEG (charge pump active) voltage at

which current into LED_ drops 10% from the value at V

LED_

= 0.5V.

Note 3: Output power is specified by a combination of a functional output current test and characterization analysis.

PARAMETER CONDITIONS MIN TYP MAX UNITS

LED DRIVER

Current-Setting Range 0.1 24.0 mA

24mA setting, TA = +25°C -2 ±1 +2

24mA setting, TA = -40°C to +85°C -5 +5

Current Accuracy

1.6mA setting, T

A

= +25°C ±5

%

Charge pump inactive 72 120

LED_ Dropout 24mA setting (Note 2)

Charge pump active 132 360

mV

LED_ Voltage-Mode Transition Threshold
(1x to 2x)

V

LED_

falling 125 150 175 mV

LED_ Voltage-Mode Transition
Hysteresis

100 mV

TA = +25°C 0.01 1

LED_ Leakage in Shutdown All LEDs off

T

A

= +85°C 0.1

µA

AUDIO AMPLIFIER

Common-Mode Bias Voltage -5% V

IN

/ 2 +5%

Output Offset Voltage VA+ = VA- = V

BIAS

, gain ≤ 12dB -25 ±1 +25 mV

Common-Mode Input Voltage 0.5

(V

IN

-

1.2)

V

Input Impedance (RIN) Table 2 10 67 140 kΩ

VIN = 3.2V 50 60

Common-Mode Rejection Ratio

f = 1kHz, V

IN

= 3.2V 70

dB

f = 217Hz 93

Power-Supply Rejection Ratio

V

A+

= VA- = V

BIAS

,

200mV

P-P

at IN

f = 1kHz 90

dB

RL = 8Ω, VIN = 3.2V 0.36 0.5

RL = 4Ω, VIN = 3.2V 0.65Output Power

THD+N = 1%,
f = 1kHz (Note 3)

R

L

= 8Ω, VIN = 5V 0.8 1.1

W

Output Current Limit 0.6 1 1.6 A

-9dB ≤ Gain ≤ 15dB ±0.13

Gain Accuracy

Gain = 18dB ±0.17

dB

Total Harmonic Distortion + Noise RL = 8Ω, f = 1kHz, P

OUT

= 0.25W, VIN = 3.2V 0.004 %

Signal-to-Noise Ratio RL = 8Ω, f = 1kHz, P

OUT

= 0.25W, VIN = 3.2V 104 dB

Maximum Capacitive Drive 500 pF

Power-Up from Shutdown Time, t

UP

See Figure 3 10 ms

Shutdown Time, t

PD

See Figure 3 3.5 µs

ELECTRICAL CHARACTERISTICS (continued)

(VIN= 3.6V, V

GND

= 0V, TA= -40°C to +85°C, unless otherwise noted. Typical values are at TA= +25°C.) (Note 1)

MAX8678

White LED Charge Pump with

1.1W Audio Amplifier

4 _______________________________________________________________________________________

Typical Operating Characteristics

(VIN= 3.2V, RL= 8Ω, TA= +25°C, unless otherwise noted.)

TOTAL HARMONIC DISTORTION +

NOISE vs. FREQUENCY

MAX8678 toc01

FREQUENCY (Hz)

THD+N (%)

10,0001000100

0.01

10 100,000

0.1

0.001

OUTPUT POWER = 150mW

OUTPUT POWER = 50mW

OUTPUT POWER = 300mW

GAIN = 3dB

TOTAL HARMONIC DISTORTION +

NOISE vs. OUTPUT POWER

MAX8678 toc02

OUTPUT POWER (W)

THD+N (%)

0.80.60.40.2

0.01

0.1

1

10

100

0.001

01.0

fIN = 1kHz

fIN = 10kHz

fIN = 100kHz

GAIN = 3dB

2000

1000

0

2.5 3.5 4.5 5.5

OUTPUT POWER vs. SUPPLY VOLTAGE

MAX8678 toc03

SUPPLY VOLTAGE (V)

OUTPUT POWER (mW)

THD+N = 10%

THD+N = 1%

0

100

300

200

400

500

0 200100 300 400 500 600 700

POWER DISSIPATION vs. OUTPUT POWER

MAX8678 toc04

OUTPUT POWER (mW)

POWER DISSIPATION POWER (mW)

0

0.4

0.2

0.8

0.6

1.0

1.2

48106 121416

OUTPUT POWER vs. LOAD RESISTANCE

MAX8678 toc05

LOAD RESISTANCE (Ω)

OUTPUT POWER (W)

THD+N = 10%

THD+N = 1%

FREQUENCY (Hz)

AMPLIFIER GAIN AND PHASE

vs. FREQUENCY

25dB

20dB

15dB

10dB

5dB

0dB

0°

-30°

-60°

-90°

MAX8678 toc06

GAIN = 18dB

10 100 1k 10k 100k

AMPLIFIER GAIN AND PHASE

FREQUENCY (Hz)

COMMON-MODE REJECTION RATIO

vs. FREQUENCY

-25dB

-35dB

-45dB

-55dB

-65dB

-75dB

-85dB

-95dB

MAX8678 toc07

GAIN = 18dB
V

RIPPLE

100mV

P-P

100 1k 10k

REJECTION RATIO

FREQUENCY (Hz)

POWER-SUPPLY REJECTION RATIO

vs. FREQUENCY

-25dB

-35dB

-45dB

-55dB

-65dB

-75dB

-85dB

-95dB

-105dB

-125dB

MAX8678 toc08

GAIN = 18dB
V

RIPPLE

18mV

P-P

100 1k 10k

REJECTION RATIO

4ms/div

AMPLIFIER STARTUP

AND SHUTDOWN

V

OUT+

V

OUT-

V

OUT+

- V

OUT-

MAX8678 toc09

V

ENAMP

2V/div

100mV/div

1V/div

1V/div