Texas Instruments UC2842D8TR

Overview

UC2842D8TR from Texas Instruments is a fixed-frequency current-mode PWM controller IC designed for off-line AC-DC and isolated DC-DC converters. It features 16 V turn-on / 10 V turn-off UVLO hysteresis, ≤1 mA start-up current, up to 500 kHz operation, 100% maximum duty cycle, and a high-current totem-pole output capable of ±1 A peak drive - enabling direct N-channel MOSFET gate control in flyback and forward topologies.

For engineers reviewing the UC2842D8TR datasheet, UC2842D8TR pinout, UC2842D8TR application, or UC2842D8TR equivalent, key selection criteria include its 8-pin SOIC (D8) package, –40°C to 85°C operating range, 5 V internal reference accuracy (±1%), pulse-by-pulse current limiting, and compatibility with standard current-sense resistor feedback in single-ended switch-mode power supplies.

Technical Context

The UC2842D8TR implements a current-mode control architecture with an integrated PWM comparator, error amplifier, undervoltage lockout with 6 V hysteresis, and oscillator using external RT/CT components. Its internal bandgap reference (5 V ±1%) feeds both the oscillator timing current and error amplifier reference node, ensuring stable frequency and regulation accuracy across temperature.

It operates in latched mode with double-pulse suppression and automatic feedforward compensation, supporting fixed-frequency operation up to 500 kHz. The totem-pole output stage is optimized for fast rise/fall times (<150 ns into 1 nF) and low saturation voltage (≤0.4 V at 20 mA sink), directly driving MOSFET gates without external buffers in medium-power applications.

Key Specifications

Pinout & Package

UC2842D8TR is housed in an 8-pin SOIC package (D8), measuring 4.90 mm × 6.00 mm, with gull-wing leads and standard JEDEC MS-012AC footprint.

Key Features

Applications

Equivalent & Alternatives

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

Compared with UC3842D8TR and TL494CDR, UC2842D8TR uniquely delivers industrial-temperature operation, true current-mode control with single-pin ISENSE interface, and full 100% duty cycle - making it the optimal choice for ruggedized off-line flyback and forward converters where reliability across thermal extremes is mandatory.

Availability

UC2842D8TR is available at Aetrix Electronics and suitable for AC-DC adapters, isolated DC-DC modules, and industrial LED drivers requiring stable component supply, long-term lifecycle support, and consistent parametric performance across manufacturing lots.

Supply support for UC2842D8TR 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 company specializing in analog, embedded processing, and power management technologies, with decades of leadership in power conversion ICs.

The UC284x series was engineered specifically for cost-sensitive, high-reliability off-line and isolated DC-DC power supplies - emphasizing minimal external component count, robust protection features, and industrial temperature resilience.

FAQ

What is the maximum switching frequency supported by UC2842D8TR?

The UC2842D8TR supports oscillator frequencies up to 500 kHz, as confirmed in Section 6.3 Recommended Operating Conditions and Figure 6-10 of the datasheet. This maximum applies under typical conditions (VCC = 15 V, TJ = 25°C) with appropriate RT/CT component selection - e.g., RRT = 5 kΩ and CCT = 1 nF yields ~344 kHz, while lower capacitance values enable operation near the 500 kHz limit. Frequency stability degrades above this point due to internal propagation delays.

Does UC2842D8TR require an external current-sense amplifier?

No, UC2842D8TR does not require an external current-sense amplifier. Its ISENSE pin accepts a direct voltage signal from a shunt resistor (typically 0.1–1 Ω), with an internal comparator threshold of 1 V (±0.1 V). The device includes built-in gain (3 V/V) and filtering capability, and supports slope compensation via external ramp injection - eliminating the need for discrete amplifiers in standard flyback or forward converter implementations.

What is the purpose of the VC pin, and is it present on UC2842D8TR?

The VC pin is absent on UC2842D8TR. It appears only on 14-pin and 20-pin variants (e.g., UC2842D14) to provide a dedicated bias supply for the output stage, decoupling gate drive current from VCC. The 8-pin SOIC package (D8) uses VCC for both logic and output stage bias, as confirmed in Table 5-1 Pin Functions and Section 7.3.1.7. Therefore, UC2842D8TR relies solely on VCC, requiring proper local bypassing (0.1 µF ceramic + bulk capacitor) to maintain drive strength.

Can UC2842D8TR be used in voltage-mode control configurations?

Yes, UC2842D8TR can be configured for voltage-mode control by applying a sawtooth ramp signal to the ISENSE pin, overriding the current-sense function. As documented in Section 7.3.1.3, this allows the PWM comparator to compare the error amplifier output against an external ramp - effectively converting the IC into a voltage-mode modulator. However, doing so forfeits pulse-by-pulse current limiting and requires careful ramp amplitude and timing alignment to avoid instability.

What is the recommended minimum timing resistor value for UC2842D8TR's RT/CT circuit?

The datasheet specifies a minimum timing resistor value of 5 kΩ for the RT/CT network (Section 5 Pin Configuration and Functions). Using a lower resistance risks excessive current draw from VREF, thermal overstress of the internal reference, and potential oscillator frequency inaccuracy or instability. For example, with CCT = 3.3 nF and RRT = 5 kΩ, fOSC ≈ 104 kHz - well within the specified 100–500 kHz operating range and safe for continuous operation.