LT3791
4
3791fb
For more information www.linear.com/LT3791
elecTrical characTerisTics
The l denotes the specifications which apply over the full operating
junction temperature range, otherwise specifications are at T
A
= 25°C (Note 2). V
IN
= 12V, V
EN/UVLO
= 12V unless otherwise noted.
PARAMETER CONDITIONS MIN TYP MAX UNITS
Open LED Falling Threshold (V
FB
)
l
1.078 1.1 1.122 V
Open LED Falling Threshold (V
(ISP-ISN)
) V
FB
= 1.2V 5 10 15 mV
Short LED Falling Threshold (V
FB
) 380 400 450 mV
OPENLED Pin Output Impedance 1.1 2.0 kΩ
SHORTLED Pin Output Impedance 1.1 2.0 kΩ
SS Latch-Off Threshold 1.75 V
SS Reset Threshold 0.2 V
Oscillator
Switching Frequency R
T
= 147k
R
T
= 59.0k
R
T
= 29.1k
190
380
665
200
400
700
210
420
735
kHz
kHz
kHz
SYNC Frequency 200 700 kHz
SYNC Pin Resistance to GND 90 kΩ
SYNC Threshold Voltage 0.3 1.5 V
Internal V
CC
Regulator
INTV
CC
Regulation Voltage 4.8 5 5.2 V
Dropout (V
IN
– INTV
CC
) I
INTVCC
= –10mA, V
IN
= 5V 240 350 mV
INTV
CC
Undervoltage Lockout 3.1 3.5 3.9 V
INTV
CC
Current Limit V
INTVCC
= 4V 67 mA
PWM
PWM Threshold Voltage 0.3 1.5 V
PWM Pin Resistance to GND 90 kΩ
PWMOUT Pull-Up Resistance 10 20 Ω
PWMOUT Pull-Down Resistance 5 10 Ω
NMOS Drivers
TG1, TG2 Gate Driver On-Resistance
Gate Pull-Up
Gate Pull-Down
V
BST
– V
SW
= 5V
2.6
1.7
Ω
Ω
BG1, BG2 Gate Driver On-Resistance
Gate Pull-Up
Gate Pull-Down
V
INTVCC
= 5V
3
1.2
Ω
Ω
TG Off to BG On Delay C
L
= 3300pF 60 ns
BG Off to TG On Delay C
L
= 3300pF 60 ns
TG1, TG2, t
OFF(MIN)
R
T
= 59.0k 240 300 ns
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 LT 3791E is guaranteed to meet performance from 0°C
to 125°C junction temperature. Specification over the -40°C to
125°C operating junction temperature range are assured by design,
characterization and correlation with statistical process controls.
The LT 3791I is guaranteed to meet performance specifications over the
–40°C to 125°C operating junction temperature range. The
LT 3791H is
guaranteed to meet performance specifications over the –40°C to 150°C
operating junction temperature range. The LT 3791MP is guaranteed to
meet performance specifications over the –55°C to 150°C operating
junction temperature range. High junction temperatures degrade operating
lifetimes. Operating lifetime is derated for junction temperatures greater
than 125°C.
Note 3: The LT 3791 includes overtemperature protection that is intended
to protect the device during momentary overload conditions. Junction
temperature will exceed the maximum operating junction temperature
when overtemperature protection is active. Continuous operation above
the specified absolute maximum operating junction temperature may
impair device reliability.
