Typical operating characteristics – Rainbow Electronics MAX1848 User Manual
Page 4
MAX1848
White LED Step-Up Converter in SOT23
4
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Typical Operating Characteristics
(See Typical Application Circuit, V+ = 3V, I
LED
= 15mA, L = 33µH, C
OUT
= 1µF, C
COMP
= 0.15µF, R
SENSE
= 5
Ω, CTRL = 1V, 2 LEDs,
T
A
= +25
°C, unless otherwise noted.)
80
82
86
84
88
90
2.5
3.5
3.0
4.0
4.5
5.0
5.5
EFFICIENCY vs. SUPPLY VOLTAGE
MAX1848 toc01
SUPPLY VOLTAGE (V)
EFFICIENCY (%)
2 LEDs
3 LEDs
I
OUT
= 15mA
90
85
80
75
70
0
30
10
20
40
50
60
EFFICIENCY vs. LOAD CURRENT
MAX1848 toc02
LOAD CURRENT (mA)
EFFICIENCY (%)
2 LEDs
3 LEDs
SWITCHING FREQUENCY
vs. SUPPLY VOLTAGE
MAX1848 toc03
SUPPLY VOLTAGE (V)
SWITCHING FREQUENCY (MHz)
1.1
1.2
1.3
1.4
2.5
3.5
3.0
4.0
4.5
5.0
5.5
T
A
= +85
°C
T
A
= +25
°C
T
A
= -40
°C
50ms/div
POWER-UP WAVEFORMS
V
CTRL
I
IN
I
LED
0
1V
38mA
0
MAX1848 toc04
15mA
0
t
RISE
= 15ms
C
COMP
= 0.15
µF
50ms/div
POWER-UP WAVEFORMS
V
CTRL
I
IN
I
LED
0
1V
38mA
0
MAX1848 toc05
15mA
0
t
RISE
= 110ms
C
COMP
= 1
µF
20
µs/div
SHUTDOWN WAVEFORMS
V
CTRL
I
IN
I
LED
0
1V
38mA
0
MAX1848 toc06
15mA
0
2
µs/div
SHUTDOWN WAVEFORMS
V
CTRL
V
OUT
V
COMP
0
1V
6.3V
4.9V
MAX1848 toc07
1.5V
0
V
OUT
EVENTUALLY
DECAYS TO V+ = 3V
5ms/div
LINE-TRANSIENT RESPONSE
V
IN
V
OUT
I
LED
3.00V
3.50V
6.25V
500mV/div
MAX1848 toc08
15mA
10mA/div
C
COMP
= 0.15
µF
20ms/div
V
CTRL
TRANSIENT RESPONSE
V
CTRL
V
OUT
I
LED
1.0V
2.0V
6.7V
6.3V
MAX1848 toc09
30mA
15mA
C
COMP
= 0.15
µF