CS2844

CS2844/3845 SERIES CS2844/CS3844 CS2845/CS3845 Current Mode PWM Control Circuit with 50% Max Duty Cycle Description The CS3844/45 provides all the necessary features to implement off-line fixed frequency current-mode control with a minimum number of external components. The CS3844 family incorporates a new precision temperature-controlled oscillator to minimize variations in frequency. An internal toggle flip-flop, which blanks the output every other clock cycle, limits the duty-cycle range to less than 50%. An undervoltage lockout ensures that VREF is stabilized before the output stage is enabled. In the CS2844/CS3844 turn on occurs at 16V and turn off at 10V. In the CS2845/CS3845 turn on is at 8.4V and turn off at 7.6V. Other features include low start-up current, pulse-by-pulse current limiting, and a high-current totem pole output for driving capacitive loads, such as gate of a power MOSFET. The output is low in the off state, consistent with N-channel devices. Features s Optimized for Offline Control s Temp. Compensated Oscillator s 50% Max Duty-cycle Clamp s VREF Stabilized before Output Stage is Enabled s Low Start-up Current s Pulse-by-pulse Current Limiting s Improved Undervoltage Lockout s Double Pulse Suppression s 1% Trimmed Bandgap Ref. s High Current Totem Pole Output Absolute Maximum Ratings Supply Voltage (ICC<30mA).........................................................................Self Limiting Supply Voltage (Low Impedance Source) .....................