Features: Synchronous Rectifier Control for High Efficiency
Programmable Volt-Second Clamp
Output Power Levels from 25W to 500W
Low Current Start-Up
True PWM Soft-Start
Low Stress Short Circuit Protection
Precision 100mV Current Limit Threshold
Adjustable Delay for Synchronous Timing
Accurate Shutdown Threshold with Programmable
Hysteresis
Programmable Slope Compensation
Programmable Leading Edge Blanking
Programmable Frequency (100kHz to 500kHz)
Synchronizable to an External Clock up to 1.5 • fOSC
Internal 1.23V Reference
2.5V External Reference
Current Mode Control
Small 16-Pin SSOP PackageApplication Telecommunications Power Supplies
Industrial and Distributed Power
Isolated and Non-Isolated DC/DC ConvertersPinout
SpecificationsVIN (Note 8) ............................................... 0.3V to 25V
SYNC, SS_MAXDC, SD_VSEC, ISENSE,
OC, COMP, BLANK, DELAY ............................ 0.3V to 6V
FB ................................................................ 0.3V to 3V
ROSC ................................................................... 50µA
VREF .................................................................... 10mA
Operating Junction Temperature Range
(Notes 2, 5) ....................................... 40°C to 125°C
Storage Temperature Range ............. 65°C to 150°C
Lead Temperature (Soldering, 10 sec).................. 300°C
Description
The LT®1952 is a current mode PWM controller optimized to control the forward converter topology, using one primary MOSFET. The LT1952 provides synchronous rectifier control, resulting in extremely high efficiency. A programmable Volt-Second clamp provides a safeguard for transformer reset that prevents saturation. This allows a single MOSFET on the primary side to reliably run at greater than 50% duty cycle for high MOSFET, transformer and rectifier utilization. The LT1952 includes soft-start for controlled exit from shutdown, overcurrent conditions and undervoltage lockout. A precision 100mV current limit threshold, independent of duty cycle, combines with soft-start to provide hiccup short circuit protection. Micropower start-up allows the LT1952 to be efficiently started from high input voltages. Programmable slope compensation and leading edge blanking allow optimization of loop bandwidth with a wide range of inductors and MOSFETs. The LT1952 can be programmed over a 100kHz to 500kHz frequency range and the part can be synchronized to an external clock. The error amplifier is a true op amp, allowing a wide range of compensation networks. The LT1952 is available in a small 16-pin SSOP package.
LT1952 Data Sheet
