MAX8821 MAXIM [Maxim Integrated Products], MAX8821 Datasheet - Page 16

• Manufacturer Part Number: MAX8821
• Description: White LED Charge Pump with Mono Class D Audio Amp and Dual LDO
• Manufacturer: MAXIM [Maxim Integrated Products]

White LED Charge Pump with Mono Class D
Audio Amp and Dual LDO
The MAX8821 integrates a charge pump for white LED
display backlighting, an audio loudspeaker amplifier,
and dual LDO for camera functions. It includes soft-
start, thermal shutdown, open-circuit and short-circuit
protections for the white LEDs, audio amplifier, and
LDOs. Figure 1 is the block diagram, and Figure 2
shows the typical application circuit.
The MAX8821 features an inverting charge pump and
six current regulators capable of 25.6mA each to drive
Figure 2. Typical Application Circuit
16
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CONTROL AND I
2.7 TO 5.5V
INPUT
DIFFERENTIAL
AUDIO INPUT
INTERFACE
Detailed Description
LOGIC
0.1μF
2.2μF
2.2μF
0.1μF
1μF
C12
C4
C5
2
C7
C3
C
LED Charge Pump
IN1
PGND1
IN2
PGND2
IN3
AGND
REF
CMREF
V
SCL
SDA
AIN+
AIN-
DD
C1P
1μF
C8
C1N
MAX8821
EP
six LEDs. The current regulators are matched to within
±1% (typ), providing uniform white LED brightness for
LCD backlight applications. To maximize efficiency, the
current regulators operate with as little as 0.15V voltage
drop. Individual white LED current regulators conduct
current to GND or NEG to extend usable battery life. In
the case of mismatched forward voltage of white LEDs,
only the white LEDs requiring higher voltage are
switched to direct current to NEG instead of GND, fur-
ther raising efficiency and reducing battery current
drain. The regulation scheme is optimized to ensure
low EMI and low input ripple. The on-chip ambient tem-
perature derating function safely allows bright 25.6mA
C2P
1μF
C9
C2N
LDO2
LED2
LED4
LED6
LDO1
SPK+
SPK-
LED3
LED5
LED1
NEG
C6
1μF
C10
2.2μF
C11
1μF
LOUDSPEAKER/EARPIECE
INDIVIDUAL
0.1mA TO
25.6mA
DIMMING
DUAL LOW-
NOISE LDO