UC1844J

The start-up current of the UC1842/3/4/5 family of control ICs is less than 1mA.

The features of the UC1842/3/4/5 family of control ICs include: - Optimized for off-line and DC to DC converters - Low start-up current (<1mA) - Automatic feed forward compensation - Pulse-by-pulse current limiting - Enhanced load response characteristics - Under-voltage lockout with hysteresis - Double pulse suppression - High current totem pole output - Internally trimmed bandgap reference - 500kHz operation - Low RO error amp These features make the UC1842/3/4/5 family of control ICs suitable for implementing off-line or DC to DC fixed frequency current mode control schemes with minimal external parts count. The differences between members of this family lie in the under-voltage lockout thresholds and maximum duty cycle ranges. The UC1842 and UC1844 have UVLO thresholds of 16V (on) and 10V (off), while the UC1843 and UC1845 have thresholds of 8.4V and 7.6V respectively. The UC1842 and UC1843 can operate to duty cycles approaching 100%, while the UC1844 and UC1845 can achieve a range of zero to 50% duty cycle by the addition of an internal toggle flip flop.

The UC1844 and UC1845 achieve a duty cycle range of zero to 50% by the addition of an internal toggle flip flop which blanks the output off every other clock cycle. This feature is not present in the UC1842 and UC1843.