Texas Instruments UC2843AQD8R

Overview

UC2843AQD8R from Texas Instruments is a current-mode PWM controller in an 8-pin SOIC package, designed for off-line and DC-DC converters. It features 8.5 V UVLO turn-on threshold, <100% maximum duty cycle, 500 kHz operation capability, ±1 A totem-pole output drive, and –40°C to 125°C extended temperature range-enabling use in industrial power supplies and battery-operated PSU designs.

For engineers reviewing the UC2843AQD8R datasheet, UC2843AQD8R pinout, UC2843AQD8R application, or UC2843AQD8R equivalent, key selection criteria include UVLO hysteresis (0.6 V), oscillator discharge current (8.3 mA typ), pulse-by-pulse current limiting, automatic feed-forward compensation, and low start-up current (<0.5 mA).

Technical Context

The UC2843AQD8R implements a fixed-frequency current-mode control architecture with a single-ended PWM output stage, internal bandgap reference (5.0 V ±1%), and error amplifier with 90 dB open-loop gain. Its oscillator uses external RT/CT components to set frequency up to 500 kHz, with trimmed discharge current enabling precise timing stability across temperature.

Under-voltage lockout ensures reliable startup at 8.5 V and release at 7.9 V, while the totem-pole output delivers ±1 A peak current into gate capacitance without external buffers. Pulse-by-pulse current limiting and double-pulse suppression prevent transformer saturation and MOSFET overstress in flyback and forward topologies.

Key Specifications

Pinout & Package

UC2843AQD8R is housed in an 8-pin SOIC (D) package measuring 4.90 mm × 6.00 mm, with standard 1.27 mm pitch and 1.75 mm max height per JEDEC MS-012 AB. Pin 1 is marked by a beveled corner or dot; the device uses standard surface-mount reflow profiles (MSL Level-1, 260°C peak).

Key Features

Applications

Equivalent & Alternatives

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

Compared with UC2843BD8R, UC2843AQD8R adds extended temperature support and lower UVLO for wider input range; versus UCC28C43DR, it trades enhanced ESD and reference precision for proven industrial qualification and broader legacy design compatibility.

Availability

UC2843AQD8R is available at Aetrix Electronics and suitable for industrial switch-mode power supplies, off-line flyback converters, and battery-operated DC-DC modules requiring stable component supply across extended temperature ranges.

Supply support for UC2843AQD8R 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 and embedded processing solutions for industrial, automotive, and personal electronics markets.

The UC284xA family was engineered specifically for current-mode control in isolated and non-isolated switched-mode power supplies, emphasizing robustness, precision timing, and ease of loop compensation in cost-sensitive power systems.

FAQ

What is the UVLO hysteresis of UC2843AQD8R?

The UC2843AQD8R has an under-voltage lockout turn-on threshold of 8.5 V and turn-off threshold of 7.9 V, resulting in 0.6 V hysteresis. This ensures clean startup and shutdown behavior during input voltage fluctuations, preventing oscillatory operation near the threshold. The hysteresis is internally fixed and does not require external components. This specification is confirmed in the Electrical Characteristics table of the UC2843AQD8R datasheet.

Can UC2843AQD8R drive a 600 V MOSFET directly?

Yes, UC2843AQD8R can directly drive medium-power 600 V MOSFETs via its ±1 A totem-pole OUTPUT pin. However, a series gate resistor (typically 5–22 Ω) is required to control dV/dt, suppress ringing, and limit peak current. Layout best practices-including short traces, local 0.1 µF bypassing at VCC, and separation of power and signal grounds-are essential for reliable 600 V switching. These requirements are documented in the UC2843AQD8R application section.

What is the maximum switching frequency supported by UC2843AQD8R?

The UC2843AQD8R supports up to 500 kHz operation, as specified in its Features list and verified in the Oscillator Section electrical characteristics. At 500 kHz, timing component selection must respect recommended ranges: RT = 5–100 kΩ and CT = 470 pF–4.7 nF. Frequency accuracy degrades slightly at extremes; typical initial oscillator accuracy is ±5% across temperature. This 500 kHz capability is explicitly stated for the UC2843AQD8R in the official TI datasheet SGLS164A.

Does UC2843AQD8R include an internal voltage reference?

Yes, UC2843AQD8R integrates a precision 5.0 V ±1% bandgap voltage reference on the VREF pin (Pin 8). It delivers up to 20 mA and exhibits 0.2–0.4 mV/°C temperature drift. This reference powers the oscillator's RT/CT network and may also supply auxiliary circuitry such as optocoupler bias or current-sense amplifiers-eliminating need for external references. All specifications are validated in the Electrical Characteristics table of the UC2843AQD8R datasheet.

How does UC2843AQD8R implement current limiting?

UC2843AQD8R implements pulse-by-pulse current limiting via the ISENSE pin (Pin 3), which feeds a comparator that resets the PWM latch each cycle when the sensed current exceeds the error amplifier's COMP voltage. The ISENSE input is internally clamped to 1.0 V, ensuring predictable trip points regardless of COMP level. This method provides immediate cycle-by-cycle protection against overloads and short circuits without requiring external latches or timers. Details are provided in the Functional Diagram and Electrical Characteristics sections of the UC2843AQD8R datasheet.