MAX1578-MAX1579 Datasheet, PDF (4/13 Pages) Maxim Integrated Products – Complete Bias and White LED Power Supplies for Small TFT Displays

Complete Bias and White LED Power Supplies
for Small TFT Displays
ELECTRICAL CHARACTERISTICS (continued)
(Circuit of Figure 3, V_IN = 3V, CTRL = ONBIAS = IN, T_A= -40°C to +85°C, typical values are at T_A= +25°C, unless otherwise noted. Note 1)
PARAMETER
CONDITIONS
MIN TYP MAX UNITS
N-CHANNEL SWITCH
LX On-Resistance
LX Leakage Current
LX Current Limit
I_LX = 190mA
V_LX = 28V, CTRL = GND
Duty cycle = 90%
0.82 1.5
Ω
T_A = +25°C
T_A = +85°C
0.01
5
µA
1
500 700 900
mA
Note 1: All devices are 100% production tested at T_A = +25°C. Limits over the operating temperature range are guaranteed by design.
Note 2: V_D1 is the forward-voltage drop of diode D1 in Figure 3.
Note 3: Time from CTRL going below the Dual-Mode threshold to IC shutdown.
Typical Operating Characteristics
(Circuit of Figure 3, V_IN = 3.6V, I_LED = 20mA, 4 LEDs, CTRL = IN, T_A = +25°C, unless otherwise noted.)
90
85
80
75
70
65
60
55
50
0
LED EFFICIENCY vs. I_LED
4 LEDs
6 LEDs
2 LEDs
8 LEDs
5
10
15
20
25
LED CURRENT (mA)
90
85
80
75
70
65
60
55
50
2.5
LED EFFICIENCY vs. V_IN
I_LED = 20mA
I_LED = 10mA
I_LED = 2mA
3.0 3.5 4.0 4.5 5.0 5.5
INPUT VOLTAGE (V)
LED CURRENT vs. TEMPERATURE
30
25
MAX1579
R_CS = 13Ω
20
15
MAX1578
10
R_CS = 22Ω
5
0
-40 -15 10
35
60
85
TEMPERATURE (°C)
LED CURRENT vs. V_CTRL
25
20
15
10
5
0
0
0.5 1.0 1.5 2.0 2.5
CTRL VOLTAGE (V)
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