Current Mode PWM Controller
SG1844/SG1845/SG3844/SG3845 Current Mode PWM Controller
Description
The SG1844/45 family of control ICs provides all th...
Description
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.
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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...
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