Datasheet LT3844 (Analog Devices) - 3

LT3844
elecTrical characTerisTics The
l
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 = 49.9k, SENSE– = SENSE+ = 10V, SGND = PGND = SW = SYNC = 0V, unless otherwise noted. PARAMETER CONDITIONS MIN TYP MAX UNITS
VCC Operating Voltage Range (Note 5) l 20 V VCC Output Voltage Over Full Line and Load Range l 8 8.3 V VCC UVLO Threshold (Rising) 6.25 V VCC UVLO Threshold Hysteresis 500 mV VCC Supply Current (Note 6) l 1.7 2.1 mA VCC Burst Mode Current VBURST_EN = 0V 95 µA VCC Shutdown Current VSHDN = 0V 20 µA VCC Current Limit l –40 –120 mA Error Amp Reference Voltage Measured at VFB Pin 1.224 1.231 1.238 V l 1.215 1.245 V VFB Pin Input Current VFB = 1.231V 25 nA SHDN Enable Threshold (Rising) l 1.3 1.35 1.4 V SHDN Threshold Hysteresis 120 mV Sense Pins Common Mode Range l 0 36 V Current Limit Sense Voltage V + – SENSE – VSENSE l 90 100 115 mV Input Current VSENSE(CM) = 0V 350 µA (I + – SENSE + ISENSE ) VSENSE(CM) = 2V –25 µA VSENSE(CM) > 4V –170 µA Operating Frequency 290 300 310 kHz l 270 330 kHz Minimum Programmable Frequency l 100 kHz Maximum Programmable Frequency l 500 kHz External Sync Frequency Range l 100 600 kHz SYNC Input Resistance 40 kΩ SYNC Voltage Threshold l 1.4 2 V Soft-Start Capacitor Control Current 2 µA Error Amp Transconductance l 270 340 410 µS Error Amp DC Voltage Gain 62 dB Error Amp Sink/Source Current ±30 µA TG Drive On Voltage (Note 7) CLOAD = 2200pF 9.8 V TG Drive Off Voltage CLOAD = 2200pF 0.1 V TG Drive Rise/Fall Time 10% to 90% or 90% to 10%, CLOAD = 2200pF 40 ns Minimum TG Off Time l 350 500 ns Minimum TG On Time l 250 350 ns
Note 1:
Stresses beyond those listed under Absolute Maximum Ratings
Note 4
: VIN voltages below the start-up threshold (7.5V) are only may cause permanent damage to the device. Exposure to any Absolute supported when the VCC is externally driven above 6.5V. Maximum Rating condition for extended periods may affect device
Note 5:
Operating range is dictated by MOSFET absolute maximum VGS. reliability and lifetime.
Note 6:
Supply current specification does not include switch drive
Note 2:
The LT3844 includes overtemperature protection that is intended currents. Actual supply currents will be higher. to protect the device during momentary overload conditions. Junction
Note 7:
DC measurement of gate drive output “ON” voltage is typically temperature will exceed 125°C when overtemperature protection is active. 8.6V. Internal dynamic bootstrap operation yields typical gate “ON” Continuous operation above the specified maximum operating junction voltages of 9.8V during standard switching operation. Standard operation temperature may impair device reliability. gate “ON” voltage is not tested but guaranteed by design.
Note 3:
The LT3844E is guaranteed to meet performance specifications from
Note 8:
The –1V absolute maximum on the SW pin is a transient condition. 0°C to 125°C junction temperature. Specifications over the –40°C to 125°C It is guaranteed by design and not subject to test. 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. 3844fc For more information www.linear.com/LT3844 3 Document Outline Features Applications Typical Application Description Absolute Maximum Ratings Order Information Electrical Characteristics Pin Configuration Typical Performance Characteristics Pin Functions Functional Diagram Operation Applications Information Typical Applications Package Description Revision History Typical Application Related Parts