SG3845

SG1844/SG1845/SG3844/SG3845 Current Mode PWM Controller Description The SG1844/45 family of control ICs provides all the required features to implement off-line Fixed Frequency, Current-mode switching power supplies with a minimum number of external components. Current-mode architecture demonstrates improved line regulation, improved load regulation, pulse-by pulse current limiting and inherent protection of the power supply output switch. The Bandgap reference is trimmed to ±1% over temperature. Oscillator discharge current is trimmed to less than ±10%. The SG1844/45 has under-voltage lockout, current-limiting circuitry and start-up current of less than 1mA. The totem-pole output is optimized to drive the gate of a power MOSFET. The output is low in the off state to provide direct interface to an Nchannel device. Both operate up to a maximum duty cycle range of zero to <50% due to an internal toggle flip-flop which blanks the output off every other clock cycle. The SG1844/45 is specified for operation over the full military ambient temperature range of -55°C to 125°C. The SG3844/45 is designed for the commercial range of 0°C to 70°C. Product Highlight Features  Optimized for Off-Line Control  Low Start-Up Current (<1mA)  Automatic Feed Forward Compensation  Trimmed Oscillator  Discharge Current  Pulse-By-Pulse Current Limiting  Enhanced Load Response Characteristics  Undervoltage Lockout with 6V Hysteresis (SG1844 only)  Double Pulse Suppression  High-Current Tot...