MAX1577Y Datasheet, PDF (4/11 Pages) Maxim Integrated Products – 1.2A White LED Regulating Charge Pump for Camera Flashes and Movie Lights

1.2A White LED Regulating Charge Pump for
Camera Flashes and Movie Lights
Typical Operating Characteristics (continued)
(V_IN = 3.6V, circuit of Figure 2, R_CS = 0.27Ω, Luxeon LXCL-PWF1 LED, T_A = +25°C, unless otherwise noted.)
LED CURRENT vs. TEMPERATURE
225
220
215
210
205 R_CS = 0.27Ω
EN1 LOW
EN2 HIGH
200
-40 -15
10
35
60
85
TEMPERATURE (°C)
LED CURRENT vs. R_CS
1.2
1.0
EN1 AND EN2 HIGH
0.8
0.6
EN1 HIGH, EN2 LOW
0.4
EN1 LOW, EN2 HIGH
0.2
0
0.2
0.4
0.6
0.8
R_CS (Ω)
TYPICAL OPERATING WAVEFORMS
IN 1x MODE
MAX1577 toc09
V_IN
50mV/div
(AC-COUPLED)
50mV/div
V_OUT
(AC-COUPLED)
V_CS
50mV/div
(AC-COUPLED)
1.0
400ns/div
TYPICAL OPERATING WAVEFORMS
IN 2x MODE
MAX1577 toc10
STARTUP AND SHUTDOWN RESPONSE
MAX1577 toc11
V_IN
50mV/div
(AC-COUPLED)
V_EN1,
V_EN2
2V/div
V_OUT
V_CS
400ns/div
LED CURRENT vs. PWM DUTY CYCLE
1200
1000
800
600
400
200
0
0
R_CS = 0.27Ω
EN1 PWM
EN2 HIGH
20
40
60
80
100
DUTY CYCLE (%)
50mV/div
(AC-COUPLED)
V_LED
50mV/div
(AC-COUPLED)
I_LED
EFFICIENCY vs. SUPPLY VOLTAGE
WITH PWM DIMMING
80
70
25%
60
50
40
50%
30
75%
20
R_CS = 0.27Ω
10
EN1 PWM
EN2 HIGH
0
2.7 3.1 3.5 3.9 4.3 4.7 5.1 5.5
SUPPLY VOLTAGE (V)
400µs/div
2V/div
0V
500mA/div
0mA
DIMMING RESPONSE
MAX1577 toc14
V_EN1
2V/div
2V/div
V_LED
0V
I_LED
500mA/div
0mA
100µs/div
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