Texas Instruments UC2842ADG4

Overview

UC2842ADG4 from Texas Instruments is a current-mode PWM controller IC designed for off-line and DC-DC switch-mode power supplies. It features 500 kHz maximum switching frequency, <0.5 mA start-up current, 8.3 mA trimmed oscillator discharge current, undervoltage lockout with 16 V turn-on/10 V turn-off hysteresis, and a 1 A totem-pole output stage. It serves as the core timing and gate drive controller in flyback and forward converter topologies.

For engineers reviewing the UC2842ADG4 datasheet, UC2842ADG4 pinout, UC2842ADG4 application, or UC2842ADG4 equivalent, key selection criteria include peak current sensing capability (1 V clamp), error amplifier open-loop gain (80 dB), UVLO behavior during brownout, duty cycle limit (<100%), and SOIC-8 package compatibility with standard PCB layouts.

Technical Context

The UC2842ADG4 implements fixed-frequency peak-current-mode control using an internal oscillator programmed via RT/CT, a high-gain error amplifier (80 dB AVOL) with 1 MHz unity-gain bandwidth, and a pulse-by-pulse current-limit comparator clamping ISENSE at 1 V. Its UVLO circuit ensures controlled startup with 16 V activation and 10 V release, while the totem-pole output delivers ±1 A gate drive current without external buffers.

It operates across –40°C to +85°C ambient temperature, draws ≤17 mA operating supply current, and maintains 5.0 V ±50 mV reference voltage accuracy over line, load, and temperature. The device supports up to 500 kHz operation and provides automatic feedforward compensation for improved transient response in AC-input converters.

Key Specifications

Pinout & Package

UC2842ADG4 is housed in an 8-pin SOIC (D) package measuring 4.90 mm × 6.00 mm, optimized for surface-mount assembly and thermal performance in power supply PCBs.

Key Features

Applications

Equivalent & Alternatives

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

Compared with UC3842BD and NCP1200DR2G, UC2842ADG4 offers superior thermal rating for industrial environments, tighter VREF accuracy for precision regulation, and a dedicated 5 V reference output enabling simpler auxiliary bias networks-making it optimal for ruggedized, mid-power SMPS designs.

Availability

UC2842ADG4 is available at Aetrix Electronics and suitable for AC-DC flyback PSUs, industrial power modules, and DC-DC buck-boost converters requiring stable component supply, long-term lifecycle support, and guaranteed traceable sourcing.

Supply support for UC2842ADG4 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

Texas Instruments is a global semiconductor leader delivering analog, embedded processing, and power management solutions with deep expertise in power conversion ICs.

The UCx84xA product line was engineered specifically for cost-effective, high-reliability current-mode switch-mode power supplies-targeting off-line AC-DC adapters, industrial PSUs, and DC-DC point-of-load regulators.

FAQ

What is the maximum operating frequency of the UC2842ADG4?

The UC2842ADG4 supports a maximum oscillator frequency of 500 kHz, as confirmed in Section 5.3 of its datasheet. This frequency is set by external RT and CT components and enables high-efficiency, compact power supply designs. Operation beyond 500 kHz is not specified or guaranteed. The UC2842ADG4 achieves this with trimmed oscillator discharge current (8.3 mA typ), ensuring stable timing across process and temperature variations.

Does the UC2842ADG4 provide a regulated reference voltage output?

Yes, the UC2842ADG4 provides a precisely trimmed 5.0 V ±50 mV reference voltage on the VREF pin under nominal conditions (TJ = 25°C, IO = 1 mA), as specified in Section 5.5. This output can source up to 10 mA and is short-circuit protected. It serves dual roles: biasing external circuitry (e.g., opto-isolator LEDs, RT/CT networks) and supplying the internal error amplifier and comparators. A 1 µF high-frequency bypass capacitor is mandatory.

How does the UC2842ADG4 implement current limiting?

The UC2842ADG4 uses pulse-by-pulse current limiting via its ISENSE pin, which accepts a voltage derived from a sense resistor in series with the power switch. When this voltage reaches 1 V, the internal comparator triggers and terminates the output pulse immediately. This 1 V clamp is internally fixed and temperature-compensated, enabling accurate, cycle-resolved overcurrent protection without external components. The feature is integral to peak-current-mode control and ensures safe operation under fault conditions.

What is the undervoltage lockout behavior of the UC2842ADG4?

The UC2842ADG4 features undervoltage lockout (UVLO) with a turn-on threshold of 16 V and turn-off threshold of 10 V, providing 6 V hysteresis. During UVLO, the output is held low, the reference is inactive, and supply current drops to ≤0.5 mA. Once VCC exceeds 16 V, the device activates fully, bringing up VREF and enabling PWM operation. This behavior prevents erratic startup and protects against brownout-induced instability in offline and DC-DC applications.

Can the UC2842ADG4 directly drive a power MOSFET?

Yes, the UC2842ADG4 integrates a high-current totem-pole output stage capable of sourcing and sinking up to 1 A, allowing direct gate drive of power MOSFETs with gate charges up to approximately 1 nF. Rise and fall times are 25–150 ns into 1 nF loads. A series gate resistor is still recommended to damp ringing and control dV/dt. This eliminates the need for external driver ICs in medium-power applications, simplifying design and reducing bill-of-materials cost for the UC2842ADG4.