UC3845BN

UC3845BN is an 8‑pin current‑mode PWM controller in the UC3842/3/4/5 family, used to regulate switch‑mode power supplies (flyback, forward, etc.). It integrates the reference, error amplifier, oscillator, peak current comparator, and protection logic, and it drives an external power transistor (MOSFET) via its PWM output.
Key points:
- External components set the switching frequency (via RT/CT) and provide compensation and feedback.
- Features typically include undervoltage lockout, overcurrent protection (with leading-edge blanking), and soft‑start.
- Common applications: offline AC‑DC adapters, DC‑DC converters, and other SMPS topologies.
- The BN suffix denotes the package variant (8‑pin) with Pb‑free/industrial temperature characteristics.
For design details (pinout, exact electrical specs, and application notes), consult the TI UC3845BN datasheet.

Equivalents for UC3845BN:
- Other UC384x family parts: UC3842, UC3843, UC3844 (pin-compatible, similar current‑mode PWM).
- Clones/cross-refs: KA3842, KA3843, KA3844, KA3845 (common drop-in replacements from various vendors).
- Other vendor clones may exist; always verify UVLO, current-sense, and drive specs to ensure compatibility.

UC3845BN is a fixed-frequency, current-mode PWM controller for off-line SMPS and DC-DC converters. Key features:
- Fixed-frequency operation (frequency set by RT/CT network).
- Internal 5V reference and transconductance error amplifier with external compensation.
- Undervoltage lockout (UVLO) on Vcc.
- Overcurrent/short-circuit protection with latch and peak current sensing (IS input).
- Line-sense/ feed-forward for better regulation over input voltage.
- Slope compensation for stable current-mode control at high duty.
- Soft-start to limit inrush and startup overshoot.
- 8-pin package (DIP-8/SO-8); suitable for drive of external switching transistor/MOSFET.
- Wide operating temperature range and general-purpose SMPS/DC-DC compatibility.

UC3845BN is an 8‑pin PWM controller (DIP-8/SO-8).
Pinout (pin 1 to 8):
- 1: COMP – error amplifier compensation input
- 2: IS – current sense input
- 3: RT/CT – timing network input (R for frequency, C for timing)
- 4: GND – ground
- 5: OUTPUT – PWM drive to external switch (MOSFET)
- 6: VREF – 5V reference output
- 7: VCC – supply voltage to the controller
- 8: NC – no connection
Used for current‑mode control in switching power supplies.

- Manufacturer: Texas Instruments (TI).
- What kind of company: An American multinational semiconductor company that designs and manufactures analog and embedded processing ICs; one of the world’s largest semiconductor manufacturers, headquartered in Dallas, Texas.

UC3845BN is a high‑speed current‑mode PWM controller for switch‑mode power supplies. Common applications include:
- Isolated and non‑isolated SMPS (flyback, forward, buck/boost)
- Offline AC adapters and wall‑wart supplies
- Battery chargers and LED drivers
- Telecom and industrial power supplies
- Monitor/TV and other consumer electronics rails
- Low‑to‑medium power DC‑DC converters using an external MOSFET
Use when a simple, cost‑effective PWM control solution is needed for regulated outputs.

UC3845BN comes in an 8-pin plastic DIP (DIP-8) package for through-hole use. Some variants are also offered in 8-pin SOIC packaging.