UC3844 Current Mode Controller IC

The UC3844A designed as a high-performance fixed frequency current mode controller explicitly for off−line and DC−to−DC converter applications. It offers the designer a cost-effective method with minimal external components with which they can obtain all the performance advantages of current mode operation.

These integrated circuits function as a trimmed oscillator for precise duty cycle control, a temperature compensated reference, a high gain error amplifier, a current sensing comparator, and a high current totem pole output ideally suited for driving a power MOSFET. Also comes with additional protective features consisting of input and reference undervoltage lockouts each with hysteresis, cycle−by−cycle current limiting, programmable output deadtime, and a latch for single pulse metering. These devices are manufactured in an 8−pin dual−in−line plastic package as well as the 14−pin plastic surface mount (SOIC−14). The SOIC−14 package comes with separate power and ground pins for the totem pole output stage.

The UC3844A feature  UYLO thresholds of 16 V (on) and 10 V (off), perfectly suited for off−line converters. The UC3844 defined as an integrated pulse width modulator (PWM) designed with both these objectives in mind. In addition, the UC3844 series optimized for efficient power sequencing of off-line converters, DC to DC regulators.  And the output stage, suitable for driving either N Channel MOSFETs or bipolar transistor switches, is low in the off state. Moreover, the UC3844A IC features a startup current of less than 0.5 mA, oscillator discharge trimmed to 8.3 mA.  And during UVLO, the output stage sinks at least 10 mA at less than 1.2V for VCC over 5V. UC3844 operates at a specified temperature ranging  from 0°C to 70°C.

Applications

• Switch Mode Power Supplies (SMPS)
• Switching regulators of any polarity
• Transformer-coupled DC-DC converters