ELECTRICAL CHARACTERISTICS The ● denotes the specifications which apply over the full operating
temperature range, otherwise specifications are at TA = 25°C. VIN = 20V, VCC = BOOST = BURST_EN = 10V, SHDN = 2V, RSET = 49.9kΩ,
SENSE– = SENSE+ = 10V, SGND = PGND = SW = SYNC = 0V, unless otherwise noted.
VCC Operating Voltage Range (Note 5)
VCC Output Voltage
VCC UVLO Threshold (Rising)
VCC UVLO Threshold Hysteresis
VCC Supply Current (Note 6)
VCC Burst Mode Current
VCC Shutdown Current
VCC Current Limit
Error Amp Reference Voltage
VFB Pin Input Current
SHDN Enable Threshold (Rising)
SHDN Threshold Hysteresis
Sense Pins Common Mode Range
Current Limit Sense Voltage
(ISENSE+ + ISENSE–)
Minimum Programmable Frequency
Maximum Programmable Frequency
External Sync Frequency Range
SYNC Input Resistance
SYNC Voltage Threshold
Soft-Start Capacitor Control Current
Error Amp Transconductance
Error Amp DC Voltage Gain
Error Amp Sink/Source Current
TG Drive On Voltage (Note 7)
TG Drive Off Voltage
TG Drive Rise/Fall Time
Minimum TG Off Time
Minimum TG On Time
Over Full Line and Load Range
VBURST_EN = 0V
VSHDN = 0V
Measured at VFB Pin
VFB = 1.231V
VSENSE+ – VSENSE–
VSENSE(CM) = 0V
VSENSE(CM) = 2V
VSENSE(CM) > 4V
CLOAD = 2200pF
CLOAD = 2200pF
10% to 90% or 90% to 10%, CLOAD = 2200pF
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 LT3844 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 specified maximum operating junction
temperature may impair device reliability.
Note 3: The LT3844E 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 LT3844I is guaranteed
over the full –40°C to 125°C operating junction temperature range.
Note 4: VIN voltages below the start-up threshold (7.5V) are only
supported when the VCC is externally driven above 6.5V.
Note 5: Operating range is dictated by MOSFET absolute maximum VGS.
Note 6: Supply current specification 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 –1V absolute maximum on the SW pin is a transient
condition. It is guaranteed by design and not subject to test.