Datasheet

LT3991/LT3991-3.3/LT3991-5
3
3991fa
elecTrical characTerisTics
Note 1: Stresses beyond those listed under Absolute Maximum Ratings
may cause permanent damage to the device. Exposure to any Absolute
Maximum Rating condition for extended periods may affect device
reliability and lifetime.
Note 2: The LT3991E is guaranteed to meet performance specifications
from 0°C to 125°C junction temperature. Specifications over the –40°C
to 125°C operating junction temperature range are assured by design,
characterization, and correlation with statistical process controls.
The l denotes the specifications which apply over the full operating
temperature range, otherwise specifications are at T
A
= 25°C. V
IN
= 12V, V
EN
= 12V, V
BD
= 3.3V unless otherwise noted. (Note 2)
The LT3991I is guaranteed over the full –40°C to 125°C operating junction
temperature range. High junction temperatures degrade operating
lifetimes. Operating lifetime is derated at junction temperatures greater
than 125°C.
Note 3: This is the minimum voltage across the boost capacitor needed to
guarantee full saturation of the switch.
Note 4: Minimum input voltage depends on application circuit.
PARAMETER CONDITIONS MIN TYP MAX UNITS
Minimum Input Voltage (Note 4)
l
4 4.3 V
Quiescent Current from V
IN
V
EN
Low
V
EN
High, V
SYNC
Low
V
EN
High, V
SYNC
Low
l
0.7
1.7
1.2
2.7
4.5
μA
μA
μA
LT3991 FB Pin Current V
FB
= 1.19V
l
0.1 12 nA
Internal Feedback Resistor Divider 10 MΩ
Feedback Voltage
l
1.175
1.165
1.19
1.19
1.205
1.215
V
V
LT3991-3.3 Output V
oltage
l
3.25
3.224
3.3
3.3
3.35
3.376
V
V
LT3991-5 Output V
oltage
l
4.93
4.89
5
5
5.07
5.11
V
V
FB Voltage Line Regulation 4.3V < V
IN
< 40V (Note 4) 0.0002 0.01 %/V
Switching Frequency R
T
= 11k
R
T
= 35.7k
R
T
= 255k
1.6
0.8
160
2
1
200
2.4
1.2
240
MHz
MHz
kHz
Minimum Switch On Time 110 ns
Minimum Switch Off Time 150 200 ns
Switch Current Limit 1.7 2.3 2.9 A
Switch V
CESAT
I
SW
= 1A 440 mV
Switch Leakage Current 0.02 1 μA
Boost Schottky Forward Voltage I
SH
= 100mA 800 mV
Boost Schottky Reverse Leakage V
REVERSE
= 12V 0.02 1 μA
Minimum Boost Voltage (Note 3) V
IN
= 5V
l
1.4 1.8 V
BOOST Pin Current I
SW
= 1A, V
BOOST
= 15V 25 33 mA
EN Voltage Threshold EN Rising
l
0.95 1.01 1.07 V
EN Voltage Hysteresis 30 mV
EN Pin Current 0.2 20 nA
LT3991 PG Threshold Offset from V
FB
V
FB
Rising 60 100 140 mV
LT3991 PG Hysteresis 20 mV
LT3991-X PG Threshold Offset from V
OUT
V
OUT
Rising 5.5 9 12.5 %
LT3991X PG Hysteresis 1.3 %
PG Leakage V
PG
= 3V 0.02 1 µA
PG Sink Current V
PG
= 0.4V
l
300 570 μA
SYNC Threshold 0.6 0.8 1.0 V
SYNC Pin Current 0.1 nA
SS Source Current V
SS
= 1V 0.6 1 1.6 μA