Texas Instruments has marked the UC3843AD as obsolete. This part is sourced through independent distribution channels — quantities are lot-specific and confirmed at RFQ. The ROHS3 compliance holds for any stock shipped, but the date-code trace and marking consistency should be verified on receipt.
Multi-topology current-mode control
The supply range spans 7.6 V to 30 V, covering common bias rails from 12 V industrial supplies up to 24 V telecom buses. Below 7.6 V the undervoltage lockout prevents the controller from starting — the input rail must hold above that threshold during the entire load transient.
Duty cycle and output drive
Maximum duty cycle is 96%, which suits flyback and forward converters that need long on-times for high step-down ratios. The single transistor-driver output drives an external N-channel MOSFET or bipolar — the gate-drive current is sourced from the Vcc pin, so the PCB trace between the supply decoupling cap and the Vcc pin should be kept short to avoid ringing on the gate waveform. The 14-SOIC package with 0.154-inch body width fits a standard SOIC-14 footprint.