STMicroelectronics UC2842BN

Overview

UC2842BN from STMicroelectronics is a high-performance current-mode PWM controller IC designed for fixed-frequency off-line and DC-DC power supplies. It features a trimmed oscillator (250 kHz guaranteed), latching PWM for cycle-by-cycle current limiting, 5 V ±1% internal reference, under-voltage lockout (16 V on / 10 V off), and a totem-pole output capable of ±1 A peak drive current - enabling direct N-channel MOSFET gate driving in flyback, forward, and boost converters.

For engineers reviewing the UC2842BN datasheet, UC2842BN pinout, UC2842BN application, or UC2842BN equivalent, key selection considerations include its 100% max duty cycle capability, low 0.5 mA start-up current, precise 2.5 V error amplifier input threshold, and compatibility with standard RC timing networks (RT/CT) for frequency tuning up to 500 kHz.

Technical Context

The UC2842BN implements current-mode control via a dedicated ISENSE comparator that terminates switch conduction when sensed inductor current reaches the error amplifier's output voltage level. Its oscillator uses an internal constant-current source charging CT through RT, generating a sawtooth waveform synchronized to PWM latch timing.

Internal circuitry includes a precision 2.5 V error amplifier with 90 dB open-loop gain and 1 MHz unity-gain bandwidth, a 5 V reference with ±25 mV load regulation, and UVLO hysteresis (6 V) ensuring reliable start-up and brown-out recovery. The output stage operates in push-pull configuration, sinking or sourcing up to 1 A with <0.4 V saturation at 20 mA.

Key Specifications

Pinout & Package

UC2842BN is supplied in an 8-pin Mini-DIP package (body width 7.95–9.75 mm, lead pitch 2.54 mm), suitable for through-hole prototyping and industrial PCB assembly.

Key Features

Applications

Equivalent & Alternatives

The following parts are listed as comparable options for similar current-mode PWM controller applications.

Compared with UC3842BN and TL494CN, the UC2842BN offers superior thermal robustness, built-in current sensing, and tighter reference tolerance - making it optimal for industrial flyback and forward converters requiring reliability across –40°C to +105°C.

Availability

UC2842BN is available at Aetrix Electronics and suitable for AC-DC adapters, flyback SMPS, and DC-DC boost converters requiring stable component supply, long-term lifecycle support, and industrial temperature qualification.

Supply support for UC2842BN includes scheduled delivery planning, volume procurement assistance, BOM continuity management, traceable sourcing, and lifecycle availability coordination for OEM customers, industrial embedded developers, connected-device designers, and electronics production programs.

Manufacturer

STMicroelectronics is a global semiconductor leader headquartered in Geneva, Switzerland, specializing in power management, analog, microcontrollers, and automotive ICs.

The UCx84xB series was developed specifically for cost-effective, high-reliability current-mode switching power supplies - targeting offline AC-DC, isolated DC-DC, and industrial power conversion where precision timing and robust fault handling are critical.

FAQ

What is the maximum operating frequency of the UC2842BN?

The UC2842BN oscillator supports frequencies up to 500 kHz using external RT/CT components. Its guaranteed minimum frequency is 250 kHz at 25°C with standard timing values (RT = 6.2 kΩ, CT = 1 nF). Frequency stability over temperature is ±0.5% across –40°C to +105°C, and line regulation holds within ±1% for VCC from 12 V to 25 V.

Does the UC2842BN require an external current sense amplifier?

No. The UC2842BN integrates a dedicated current sense comparator referenced to 1 V (typ.) at the ISENSE pin, eliminating the need for external amplification. It accepts a direct voltage signal from a shunt resistor or current transformer secondary, with input bias current ≤ –10 µA and propagation delay of 150–300 ns - sufficient for accurate cycle-by-cycle limiting in flyback and forward converters.

Can the UC2842BN drive a P-channel MOSFET directly?

No. The UC2842BN OUTPUT pin is a totem-pole stage optimized for sinking current into the gate of an N-channel MOSFET. Driving a P-channel device would require level-shifting circuitry or an external driver, as the output does not provide high-side gate drive capability or bootstrap support. Its design assumes low-side N-MOSFET switching in common topologies like flyback and boost.

How does the UC2842BN handle overvoltage on the VCC pin?

The UC2842BN includes an internal 36 V zener clamp on the VCC pin, limiting input voltage during transients. Absolute maximum rating is 30 V from a low-impedance source; above that, the zener conducts to protect internal circuitry. For sustained operation, VCC must remain between 10 V (UVLO release) and 25 V to ensure stable reference and oscillator performance - external TVS or series resistor may be added for harsh environments.