PWM controller, 11 V - 30 Vi, 500kHz, 1.6 ... 13 Vout, SO-8

Powerful PWM controller in current mode

Description:

The UC384xB family of control ICs provides the features necessary to implement fixed frequency offline or DC-to-DC current control schemes with a minimal number of external components. Internally implemented circuitry includes a trimmed oscillator for precise DUTY-CYCLE CONTROL under voltage lockout with a starting current of less than 0.5 mA, a precision reference trimmed for accuracy at the fault current input, logic to ensure latched operation, a PWM comparator that also provides current limit control, and a totem-pole output stage designed to deliver or sink a high peak current. The output stage, which is suitable for driving N-channel MOSFETs, is low in the off-state. The differences between the members of this family are in the undervoltage lockout thresholds and maximum duty cycle ranges. The UC3842B and UC3844B have UVLO thresholds of 16V (on) and 10V (off), ideally suited for off-line applications. The corresponding thresholds for the UC3843B and UC3845B are 8.5V and 7.9V. The UC3842B and UC3843B can operate with duty cycles that are close to 100%. A range from zero to <50% is achieved on the UC3844B and UC3845B by adding an internal toggle flip-flop that mutes the output every other clock cycle.

Features
- trimmed oscillator for precise frequency control
- oscillator frequency guaranteed at 250 khz
- current operating mode up to 500 khz
- automatic forward compensation
- latching PWM for cycle-by-cycle current limiting
- internally trimmed reference with undervoltage lockout
- high-current totem pole output
- undervoltage lockout with hysteresis
- low starting and operating current