LT3845
4
3845fd
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 LT3845 includes overtemperature protection that is intended
to protect the device during momentary overload conditions. Junction
temperature will exceed 125°C when overtemperature protection is active.
Continuous operation above the specifi ed maximum operating junction
temperature may impair device reliability.
Note 3: The LT3845E is guaranteed to meet performance specifi cations
from 0°C to 125°C junction temperature. Specifi cations over the –40°C
to 125°C operating junction temperature range are assured by design,
characterization and correlation with statistical process controls. The
LT3845I is guaranteed over the full –40°C to 125°C operating junction
temperature range. The LT3845MP is 100% tested and guaranteed over
the –55°C to 125°C temperature range.
Note 4: V
IN
voltages below the start-up threshold (7.5V) are only
supported when the V
CC
is externally driven above 6.5V.
Note 5: Operating range is dictated by MOSFET absolute maximum V
GS
.
Note 6: Supply current specifi cation does not include switch drive
currents. Actual supply currents will be higher.
Note 7: DC measurement of gate drive output “ON” voltage is typically
8.6V. Internal dynamic bootstrap operation yields typical gate “ON”
voltages of 9.8V during standard switching operation. Standard operation
gate “ON” voltage is not tested but guaranteed by design.
Note 8: The –2V absolute maximum on the SW pin is a transient condition.
It is guaranteed by design and not subject to test.
ELECTRICAL CHARACTERISTICS
The l denotes the specifi cations which apply over the full operating
temperature range, otherwise specifi cations are at T
A
= 25°C. V
IN
= 20V, V
CC
= BOOST = BURST_EN = 10V, SHDN = 2V, R
SET
= 49.9kΩ,
SENSE
–
= SENSE
+
= 10V, SGND = PGND = SW = SYNC = 0V, unless otherwise noted.
PARAMETER CONDITIONS MIN TYP MAX UNITS
TG, BG Drive On Voltage (Note 7)
TG, BG Drive Off Voltage
C
LOAD
= 3300pF
C
LOAD
= 3300pF
9.8
0.1
V
V
TG, BG Drive Rise/Fall Time 10% to 90% or 90% to 10%, C
LOAD
= 3300pF 50 ns
Minimum TG Off Time
●
350 650 ns
Minimum TG On Time
●
250 400 ns
Gate Drive Nonoverlap Time TG Fall to BG Rise
BG Fall to TG Rise
200
150
ns
ns
