LT1243IS8#PBF

LT1243 is an 8-pin, fixed frequency, current mode, pulse width modulator. It is improved plug compatible versions of the industry standard UC1842 series. This device has both improved speed and lower quiescent current. It is optimized for off-line and DC/DC converter applications. It contains a temperature-compensated reference, high gain error amplifier, current sensing comparator 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 output stage have been eliminated, making 500KHz operation practical. Several new features have been incorporated. Leading edge blanking has been added to the current sense comparator. Trims have been added to the oscillator circuit for both frequency and sink current, and both of these parameters are tightly specified. Applications include off-line converters and DC/DC converters.

• Low start-up current of less than 250µA, 50ns current sense delay, 10mA maximum operating current
• Current mode operation to 500KHz
• 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, 96% maximum duty cycle
• 0.75V typical output low level at IOUT = 200mA and 11.75V minimum output high level at IOUT = 200mA
• 50ns typical rise time at CL = 1nF, TJ = 25°C and 30ns typical fall time at CL = 1.0nF, TJ = 25°C
• 8.4V typ start-up threshold, 7.6V minimum operating voltage, 0.8V typ hysteresis (UVLO)
• 8-lead plastic SO package, -40°C to 125°C temperature range

Notes

ADI products are only authorized (and sold) for use by the customer and are not to be resold or otherwise passed on to any third party