The UC3849 is a secondary side average current mode controller produced by TI company. It has a 1MHz operation frequency, supports differential AC switching current sensing, accurate programmable maximum duty cycle, multiple chips can be synchronized to the fastest oscillator, wide gain bandwidth product (70MHz, Acl>10) voltage error and current sense amplifiers, and up to 10 devices can easily share a common load.
The UC2849/UC3849 family are secondary‑side average current‑mode controllers designed for isolated power supplies. They offer practical secondary‑side control, differential AC current sensing, programmable maximum duty cycle, and the ability to synchronize up to ten devices to the fastest oscillator.
The document includes a block diagram, connection diagrams for DIL‑24, SOIC‑24 and PLCC‑28 packages, absolute maximum ratings, recommended operating conditions, detailed electrical specifications, pin function descriptions, and mechanical dimensions of the plastic small‑outline package.
| Supply Voltage (Vcc) | 20 V |
|---|---|
| Output current source or sink | 0.3 A |
| Analog input voltage range | 0.3 to 7 V |
| Share bus voltage | 0 to 6.2 V |
Up to ten UC3849 devices can be connected in parallel for load sharing and oscillator synchronization.
The recommended input voltage is 8 V to 20 V.
The VREF pin provides a reference voltage of 5.0 V.
The maximum duty cycle can be set up to 90 % (typical 80 %–85 %).