LT1246 Datasheet | Linear Technology

LT1246/LT1247 1MHz Off-Line Current Mode PWM and DC/DC Converter DESCRIPTIO The LT®1246/LT1247 are 8-pin, fixed frequency, current mode, pulse width modulators. These devices are designed to be improved plug patible versions of the industry standard UC1842 PWM circuit. The LT1246/ LT1247 are optimized for off-line and DC/DC converter applications. They contain a temperature pensated reference, high gain error amplifier, current sensing parator, and a high current totem pole output stage ideally suited to driving power MOSFETs. Start-up current has been reduced to less than 250µA. Cross-conduction current spikes in the totem pole output stage have been eliminated, making 1MHz operation practical. Several new Features have been incorporated. Leading edge blanking has been added to the current sense parator. This minimizes or eliminates the filter that is normally required. Eliminating this filter allows the current sense loop to operate with minimum delays. Trims have been added to the oscillator circuit for both frequency and sink current, and both of these parameters are tightly specified. The output stage is clamped to a maximum VOUT of 18V in the on state. The output and the reference output are actively pulled low during under-voltage lockout. , LTC and LT are registered trademarks of Linear Technology Corporation. Features s s s s s s s s s s s s Current Mode Operation to 1MHz 30ns Current Sense Delay < 250µA Low Start-Up Current Current Sense Leading Edge Blanking Pin patible with UC1842 Undervoltage Lockout with Hysteresis No Cross-Conduction Current Trimmed Bandgap Reference 1A Totem Pole Output Trimmed Oscillator Frequency and Sink Current Active Pull-Down on Reference and Output During Undervoltage Lockout 18V High Level Output Clamp APPLICATI s s Off-Line Converters DC/DC Converters Start-Up Threshold 16V 8.4V Minimum Operating Voltage 10V 7.6V Maximum Duty Cycle 100% 100% Device LT1246 LT1247 Replaces UC1842 UC1843 BLOCK...