
Ultra-Efficient Negative Charge-Pump LED
Driver with Dual LDOs in 3mm x 3mm Thin QFN
Typical Operating Characteristics (continued)
(V IN = 3.6V, V EN_ = V IN , Circuit of Typical Operating Circuit, T A = +25°C, unless otherwise noted.)
17.0
16.8
LED CURRENT MATCHING
vs. SUPPLY VOLTAGE
TYPICAL OPERATING WAVEFORMS
(CHARGE PUMP INACTIVE)
MAX8822 toc11
16.6
16.4
16.2
16.0
15.8
15.6
15.4
V IN
I IN
I LED1
10mV/div
(AC-COUPLED)
100mA (AC-COUPLED)
10mA/div
24mA (AC-COUPLED)
10mA/div
15.2
15.0
2.7
3.1
3.5
3.9
16mA/LED, V IN FALLING
4.3 4.7 5.1
5.5
4 LEDs, 24mA/LED,
V IN = 3.8V
400ns/div
SUPPLY VOLTAGE (V)
TYPICAL OPERATING WAVEFORMS
(CHARGE PUMP ACTIVE)
MAX8822 toc12
STARTUP AND SHUTDOWN
MAX8822 toc13
5V/div
V ENLED
0V
V IN
I IN
10mV/div
(AC-COUPLED)
100mA (AC-COUPLED)
V IN
24mV/div
(AC-COUPLED)
10mA/div
I IN
100mA/div
I LED1
24mA (AC-COUPLED)
10mA/div
0A
4 LEDs, 24mA/LED,
V IN = 3.2V
400ns/div
SERIAL-PULSE CONTROL
DIMMING RESPONSE
MAX8822 toc14
I LED_TOTAL
I LED_ = 24mA
1ms/div
SERIAL-PULSE CONTROL LDO
VOLTAGE PROGRAMMING
MAX8822 toc15
100mA/div
0A
5V/div
V ENLED
7 PULSES 0V
0
5V/div
I LED1
24mA
14.4mA 10mA/div
0A
V ENLDO
I LDO2
8 PULSES
1.8V
1V/div
0V
3.3V
I IN
1ms/div
4 LEDs
50mA/div
0A
I LDO1
I LDO1 = I LDO2 = 100mA
400 μ s/div
2V/div
0V
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