MAX8678 Datasheet, PDF (1/13 Pages) Maxim Integrated Products – White LED Charge Pump with 1.1W Audio Amplifier

19-0786; Rev 0; 4/07
White LED Charge Pump with
1.1W Audio Amplifier
General Description
The MAX8678 integrates a charge pump for white light-
emitting 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 main-
tained 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 single-
wire serial-pulse interface. Clicks and pops are sup-
pressed 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 avail-
able 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
Typical Operating Circuit
INPUT
2.7V TO 5.5V
1μF
4.7μF
LED ON/OFF
AND DIMMING
AMP ON/OFF
AND GAIN
DIFFERENTIAL
AUDIO
INPUT
C+
IN
GND
C-
LED1
LED2
LED3
LED4
ENLED _{MAX8678 BIAS}
BACKLIGHT
OR FLASH
0.1mA TO
24mA
0.1μF
ENAMP
A+
A-
EP
OUT+
OUT-
NEG
LOUDSPEAKER
8Ω
1μF
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, V_IN = 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
Ordering Information
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 extend-
ed temperature range.
Pin Configuration
TOP VIEW
12 11 10 9
NEG 13
C- 14
C+ 15
MAX8678
ENLED 16
+
8 BIAS
7 OUT-
6 OUT+
5 ENAMP
1
2
3
4
THIN QFN
3mm × 3mm
________________________________________________________________ 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.