Datasheet

LT3991/LT3991-3.3/LT3991-5
6
3991fa
Typical perForMance characTerisTics
EN Threshold
Boost Diode Forward Voltage Power Good Threshold
Minimum Input Voltage
T
A
= 25°C, unless otherwise noted.
Transient Load Response,
Load Current Stepped from 25mA
(Burst Mode Operation) to 525mA
Minimum Input Voltage
LOAD CURRENT (mA)
0
INPUT VOLTAGE (V)
5.0
4.8
4.0
3.4
3.6
4.2
4.4
4.6
3.8
3.2
3.0
800400
3991 G19
1200600200 1000
TO START
TO RUN
V
OUT
= 3.3V
LOAD CURRENT (mA)
0
INPUT VOLTAGE (V)
6.4
6.2
5.4
5.6
6.0
5.8
5.2
5.0
800400
3991 G20
1200600200 1000
TO START
TO RUN
V
OUT
= 5V
TEMPERATURE (°C)
THRESHOLD VOLTAGE (V)
3971 G21
1.05
0.97
0.96
1.03
1.02
1.01
1.00
0.99
0.98
1.04
0.95
–55 15535 65 125955–25
RISING THRESHOLD
FALLING THRESHOLD
BOOST DIODE CURRENT (mA)
BOOST DIODE VF (V)
3991 G22
1.6
0.4
0.2
1.2
1.0
0.8
0.6
1.4
0
0 1500500 750 12501000250
TEMPERATURE (°C)
THRESHOLD VOLTAGE (%)
3991 G23
95
88
87
86
93
92
91
90
89
94
85
–55 15535 65 125955–25
10µs/DIV
3991 G24
V
OUT
100mV/DIV
I
L
500mA/DIV
V
IN
= 48V, V
OUT
= 3.3V
C
OUT
= 47µF
Minimum Switch On-Time/
Switch Off-Time
Soft-StartLT3991-X Frequency Foldback
TEMPERATURE (°C)
–55
SWITCH ON/OFF TIME (ns)
400
350
150
50
200
250
300
100
0
655
3991 G17
15535–25 95 125
t
OFF(MIN)
1A LOAD
t
OFF(MIN)
0.5A LOAD
t
ON(MIN)
SS PIN VOLTAGE (V)
0
SWITCH CURRENT LIMIT (A)
2.5
2.0
0.5
1.0
1.5
0
1.250.75
3991 G18
210.50.25 1.751.5
V
OUT
(% OF REGULATION VOLTAGE)
0
0
SWITCHING FREQUENCY (kHz)
100
300
400
500
40
80
100
900
3991 G30
200
20 60
600
700
800