MAX8821 Datasheet, PDF (1/29 Pages) Maxim Integrated Products – White LED Charge Pump with Mono Class D Audio Amp and Dual LDO

19-1014; Rev 0; 10/07
White LED Charge Pump with Mono Class D
Audio Amp and Dual LDO
General Description
The MAX8821 integrates a charge pump for white
LEDs, an audio loudspeaker amplifier, and two low-
noise LDOs controlled by an I²C control interface. The
high-efficiency, adaptive-mode inverting charge pump
drives up to six LEDs with constant current for uniform
brightness. The LED current is controlled by an I²C
interface and adjusts from 0.1mA to 25.6mA per LED
into 32 pseudo-logarithmic steps. Independent volt-
ages for each LED maximize efficiency even with large
LED forward voltage (V_F) mismatch. An internal temper-
ature derating function reduces the current above
+40°C to protect the LEDs.
The high-efficiency mono Class D audio amplifier deliv-
ers up to 2W into a 4Ω speaker from a 5V input supply.
The amplifier features proprietary filterless Active
Emissions Limiting (AEL) technology. AEL prevents
high-frequency emissions resulting from conventional
Class D free-wheeling behavior in the presence of an
inductive load. The amplifier offers two modulation
schemes: a fixed-frequency mode (FFM) and a spread-
spectrum mode (SSM) that reduce EMI-radiated emis-
sions due to the modulation frequency. The amplifier
also has robust output protection and high power-sup-
ply rejection ratio (PSRR). Click-and-pop suppression is
active during power-up/down, enable/disable, and for
all mode changes. The amplifier’s gain is adjustable
through an I²C interface, from -3dB to +24dB in 10 3dB
steps. Differential inputs improve common-mode noise
rejection.
The LDOs in the MAX8821 are designed for low-noise
operation. Each LDO output voltage can be individually
programmed by the I²C interface. Both LDO1 and
LDO2 have a high 70dB PSRR rating.
The MAX8821 includes soft-start, thermal shutdown,
open-circuit, and short-circuit protections, and is avail-
able in a compact 28-pin, Thin QFN, 4mm x 4mm pack-
age (0.8mm max height).
Applications
Cell Phones and Smartphones
PDAs, Digital Cameras, Camcorders
MP3 Players, GPS Devices
Features
♦ White LED Inverting Charge Pump
Independent Adaptive Current Regulators for
Each LED
6 Low-Dropout Current Regulators
Flexible I²C Dimming Control for Each LED
Ramp-Up/Down, Current Control for Each LED
Low 70µA (typ) Quiescent Current
T_A Derating Function Protects LEDs
♦ Mono 2W Class D Loudspeaker Amplifier
85% Efficiency (R_L = 8Ω, P_OUT = 600mW)
Low 0.05% THD+N at 1kHz
High 65dB PSRR at 1kHz
Fully Differential Inputs
-3dB to +24dB Gain Settings in 3dB Steps
Integrated Click-and-Pop Suppression
Low Quiescent Current
♦ Dual Low-Noise LDO
45µV_RMS Output Noise, 70dB PSRR
Flexible I²C-Controlled Output Voltages
200mA and 300mA Output Current Drive
Ordering Information
PART
TEMP RANGE
PIN-
PACKAGE
PKG
CODE
MAX8821ETI+ -40°C to +85°C
28 Thin QFN
4mm x 4mm
T2844-1
+Denotes a lead-free package.
Typical Operating Circuit
INPUT
2.7 TO 5.5V
LOGIC
CONTROL AND I2C
INTERFACE
DIFFERENTIAL
AUDIO INPUT
C1P
IN1
PGND1
IN2
PGND2
IN3
AGND
REF
CMREF
C1N C2P
MAX8821
C2N
NEG
LED1
LED2
LED3
LED4
LED5
LED6
LDO1
VDD
LDO2
SDA
SCL
AIN+
SPK+
AIN-
SPK-
EP
INDIVIDUAL
0.1mA TO
25.6mA
DIMMING
DUAL LOW
NOISE LDO
LOUDSPEAKER/
EARPIECE
________________________________________________________________ Maxim Integrated Products 1
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