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.

• 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
• Double-Pulse Suppression
• High-Current Totem-Pole Output (1A Peak)
• Internally Trimmed Band-gap Reference
• 500kHz Operation SG1845 - 8.4 Volts
• Low Shoot-Through Current <75mA Over Temperature