MAX8822 Ver la hoja de datos (PDF) - Maxim Integrated
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MAX8822
Maxim Integrated
MAX8822 Datasheet PDF : 15 Pages
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Ultra-Efficient Negative Charge-Pump LED
Driver with Dual LDOs in 3mm x 3mm Thin QFN
1
ENLED
2
3
4
tINIT
INTERNAL
CURRENT SHDN 24.0mA
SETTING
22.4mA 20.8mA
tHOLD
2.5ms
19.2mA
ILED_
SHDN
1
2
3
13
14
tHI
tLO
24.0mA 22.4mA 20.8mA
19.2mA
tHOLD
2.5ms
5.6mA 4.8mA
Figure 1. Timing Characteristics for LED Serial-Pulse Control Interface
0
ENLDO
1
2
3
t INIT
INTERNAL
LDO1
SHDN 0V
2.8V
SETTING
INTERNAL
LDO2
SHDN 0V
1.2V
SETTING
tHOLD
2.5ms
3.3V 2.8V
1.2V 1.5V
1
2
3
tHI
tLO
2.8V
3.3V
2.8V
1.2V
1.2V
1.5V
2.8V
SHDN
VLDO1
1.5V
SHDN
VLDO2
Figure 2. Timing Characteristics for LDO Serial-Pulse Control Interface
12
13
tHOLD
2.5ms
0V
1.8V
2.8V 0V
tINIT = 120μs
tHI = 500ns TO 500μs
tLO = 500ns TO 500μs
tSHDN
2.5ms
SHDN
4.8mA
SHDN
tINIT = 120μs
tHI = 500ns TO 500μs
tLO = 500ns TO 500μs
tSHDN
2.5ms
SHDN
1.8V
SHDN
0V
SHDN
Detailed Description
The MAX8822 drives up to four white LEDs (WLEDs) with
regulated constant current for display backlighting in cell
phones, cameras, PDAs, and other handheld devices.
The IC also includes two low-noise, high-PSRR, 200mA
LDOs for powering camera modules or other devices.
Figure 3 depicts the MAX8822 block diagram.
The MAX8822 IC utilizes a 0.5x inverting charge pump
and extremely low-dropout current regulators to
achieve high efficiency over the full 1-cell Li+ battery
voltage range. The charge pump remains inactive
unless the LED current regulators require additional
voltage to prevent them from entering dropout. To max-
imize efficiency, the current regulators operate with as
little as 150mV voltage drop. Additionally, each LED
current regulator is independently monitored and
switched, ensuring the least possible power consump-
tion to extend battery life (see the Adaptive Current
Regulator Switchover section for details).
8 _______________________________________________________________________________________
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