Datasheet LT3837 (Analog Devices) - 3

LT3837
ELECTRICAL CHARACTERISTICS The
l
denotes specifications which apply over the full operating junction temperature range, otherwise specifications are TA = 25°C. VCC = 14V; PG, SG Open; VC = 1.4V, VSENSE = 0, RCMP = 1k, RTON = 90k, RPGDLY = 27.4k, RENDLY = 90k, unless otherwise specified. PARAMETER CONDITIONS MIN TYP MAX UNITS
Feedback Amplifier Voltage Gain VC = 1.2V to 1.7V 1400 V/V Soft-Start Charging Current VSFST = 1.5V 16 20 25 µA Soft-Start Discharge Current VSFST = 1.5V, VUVLO = 0V 0.7 1.3 mA Control Pin Threshold (VC) Duty Cycle = Min 1.0 V
Gate Outputs
PG, SG Output High Level l 6.6 7.4 8.0 V PG, SG Output Low Level l 0.01 0.05 V PG, SG Output Shutdown Strength VUVLO = 0V; IPG, ISG = 20mA l 1.6 2.3 V PG Rise Time CPG = 1nF 11 ns SG Rise Time CSG = 1nF 15 ns PG, SG Fall Time CPG, CSG = 1nF 10 ns
Current Amplifier
Switch Current Limit at Maximum VC VSENSE + l 88 98 110 mV ∆VSENSE/∆VC 0.07 V/V Sense Voltage Overcurrent Fault Voltage VSENSE + 206 230 mV
Timing
Switching Frequency (fOSC) COSC = 100pF l 84 100 110 kHz Oscillator Capacitor Value (COSC) (Note 6) 33 200 pF Minimum Switch On Time (tON(MIN)) 200 ns Flyback Enable Delay Time (tED) 265 ns PG Turn-On Delay Time (tPGDLY) 200 ns Maximum Switch Duty Cycle l 85 88 % SYNC Pin Threshold l 1.53 2.1 V SYNC Pin Input Resistance 40 kΩ
Load Compensation
Load Comp to VSENSE Offset Voltage VRCMP with VSENSE+ = 0 0.8 mV Feedback Pin Load Compensation Current VSENSE+ = 20mV 20 µA
UVLO Function
UVLO Pin Threshold (VUVLO) l 1.215 1.240 1.265 V UVLO Pin Bias Current VUVLO = 1.2V –0.25 0.1 0.25 µA VUVLO = 1.3V –4.50 –3.4 –2.50 µA
Note 1:
Stresses beyond those listed under Absolute Maximum Ratings
Note 3:
The LT3837E is guaranteed to meet performance specifications may cause permanent damage to the device. Exposure to any Absolute from 0°C to 85°C. Specifications over the –40°C to 125°C operating Maximum Rating condition for extended periods may affect device junction temperature range are assured by design, characterization and reliability and lifetime. correlation with statistical process controls. The LT3837I is guaranteed to
Note 2:
This IC includes overtemperature protection that is intended meet performance specifications over the full –40°C to 125°C operating to protect the device during momentary overload conditions. Junction junction temperature range. temperature will exceed 125°C when overtemperature protection is active.
Note 4:
TJ is calculated from the ambient temperature TA and power Continuous operation above the specified maximum operating junction dissipation PD according to the following formula: temperature may impair device reliability. TJ = TA + (PD • 40°C/W)
Note 5:
Supply current does not include gate charge current to the MOSFETs. See the Applications Information section.
Note 6:
Component value range guaranteed by design. 3837fd 3 Document Outline features applications description Typical Application absolute maximum ratings Pin Configuration order information electrical characteristics typical performance characteristics pin functions block diagram flyback feedback amplifier timing diagram operation applications information typical application Package description Revision History related parts