The NCP4328 is an auxiliary-side SMPS controller for applications requiring constant voltage and/or constant current regulation. The NCP4328x consists of two OTA amplifiers for voltage and current loop regulation with a precise internal voltage reference. The output of the OTA is an open-drain type (only the OTA sinks current). The NCP4328B includes an LED driver pin implemented with an open MOSFET driven by a 1 kHz square wave, operating at a 12.5% duty cycle for indication when VCC is above UVLO. The NCP4328A uses TSOP5 encapsulation, while the NCP4328B uses TSOP6 encapsulation.