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.
Feature
- 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 Totem-Pole Output
- Internally Trimmed Bandgap Reference
- 500kHz Operation
- Under-voltage Lockout: SG1844 - 16 Volts, SG1845 - 8.4 Volts
- Low Shoot-through Current <75mA Over Temperature
