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2022-09-24 23:33:15
LT1246-1MHz Offline Current Mode PWM and DC/DC Converter
The LT®1246/LT1247 are 8-pin, fixed frequency, current mode, pulse width modulators. These devices are designed to improve plug-in compatible 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 compensated reference, high gain error amplifier, current sense comparator, and high current totem pole output stage ideal for driving power MOSFETs. The startup current has been reduced to less than 250 mA. The peak of the cross-conduction current in the totem-pole output stage is eliminated, and 1MHz operation is practical. Some new features have been incorporated. Leading edge blanking has been added to the current sense comparators. This minimizes or eliminates the filters usually required. Eliminating this filter allows the current sensing loop with the lowest delay. Trim has been added to the oscillator circuit frequency and sink current, these parameters are strictly specified. The output stage is clamped to the state for a maximum output voltage of 18V. The output and the reference output are actively pulled low during undervoltage lockout.