UC3844, UC3845, UC2844,
UC2845
High Performance
Current Mode Controllers
The UC3844, UC3845 series are high performance fixed frequency
current mode controllers. They are specifically designed for Off?Line
and DC?to?DC converter applications offering the designer a cost
effective solution with minimal external components. These integrated
circuits feature an oscillator, a temperature compensated reference, high
gain error amplifier, current sensing comparator, and a high current
totem pole output ideally suited for driving a power MOSFET.
Also included are protective features consisting of input and
reference undervoltage lockouts each with hysteresis, cycle?by?cycle
current limiting, a latch for single pulse metering, and a flip?flop which
blanks the output off every other oscillator cycle, allowing output dead
times to be programmed for 50% to 70%.
These devices are available in an 8?pin dual?in?line plastic package
as well as the 14?pin plastic surface mount (SOIC?14). The SOIC?14
package has separate power and ground pins for the totem pole output
stage.
The UCX844 has UVLO thresholds of 16 V (on) and 10 V (off),
ideally suited for off?line converters. The UCX845 is tailored for
lower voltage applications having UVLO thresholds of 8.5 V (on) and
7.6 V (off).