UC3845AM

Product Summary

The UC3845AM of control IC provides all the necessary features to implement off-line fixed-frequency, current-mode switching power supplies with a minimum of external components. The current mode architecture demonstrates improved load regulation, pulse by pulse current limiting and inherent protection of the power supply output switch. The IC includes: A bandgap reference trimmed to ±1% accuracy, an error amplifier, a current sense comparator with internal clamp to 1V, a high current totem pole output stage for fast switching of power MOSFETs, and an externally programmable oscillator to set frequency and maximum duty cycle. The undervoltage lock-out is designed to operate with 250μA typ. start-up current, allowing an efficient bootstrap supply voltage design. Available options for this family of products, such as start-up voltage hysteresis and duty cycle, are summarized below in the Available Options section. The UC3845AM of control ICs is also available in 14 pin SOIC package which makes the Power Output Stage Collector and Ground pins available.

Parametrics

Absolute maximum ratings: (1)Supply Voltage (Low Impedance Source) (VCC): 30V; (2)Supply Voltage (ICC < 30mA): Self Limiting; (3)Output Current: ±1A; (4)Output Energy (Capacitive Load): 5μJ; (5)Analog Inputs (VFB & ISENSE): -0.3V to +6.3V; (6)Error Amp Output Sink Current: 10mA; (7)Power Dissipation at TA = 25℃ (M Package): 1W; (8)Storage Temperature Range:-65℃ to +150℃; (9)Lead Temperature (Soldering, 10 Seconds): 300℃.

Features

Features: (1)low start-up current (0.5mA max.); (2)trimmed oscillator discharge current; (3)optimized for off-line and dc-to-dc converters; (4)automatic feed forward compensation; (5)pulse-by-pulse current limiting; (6)enhanced load response characteristics; (7)under-voltage lockout with hysteresis; (8)double pulse suppression; (9)high-current totem pole output; (10)internally trimmed bandgap reference; (11)500KHz operation; (12)low ro error amplifier.

Diagrams