The UC2901 is designed to solve many of the problems associated with closing a feedback control loop across a voltage isolation boundary. As a stable and reliable alternative to an optical coupler, UC2901 features an amplitude modulation system that allows a loop error signal to be coupled with a small RF transformer or capacitor.
The programmable, high-frequency oscillator within the UC2901 permits the use of smaller, less-expensive transformers, which can readily be built to meet the isolation requirements of todays line-operated power systems. As an alternative to RF operation, the external clock input to these devices allows synchronization to a system clock or to the switching frequency of an SMPS.
An additional feature is a status monitoring circuit that provides an active low output when the sensed error voltage is within ±10% of the reference. The DRIVERA output, DRIVERB output, and STATUS output are disabled until the input supply has reached a sufficient level to allow proper operation of the device.
Because these devices also can be used as a DC driver for optical couplers, the benefits of 4.5 V to 40 V supply operation, a 1% accurate reference, and a high-gain general-purpose amplifier offer advantages, even though an AC system may not be desired.
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