Texas Instruments UC3844ADTRG4

Overview

UC3844ADTRG4 from Texas Instruments is a current-mode PWM controller IC designed for off-line and DC-DC switch-mode power supplies, featuring 16 V UVLO turn-on threshold, 10 V UVLO hysteresis, ≤50% maximum duty cycle, 8.3 mA trimmed oscillator discharge current, and 1 A totem-pole gate driver output - deployed in universal-input flyback converters for industrial PSUs.

For engineers reviewing the UC3844ADTRG4 datasheet, UC3844ADTRG4 pinout, UC3844ADTRG4 application, or UC3844ADTRG4 equivalent, key selection criteria include its fixed-frequency peak-current-mode control architecture, SOIC-8 package compatibility, 500 kHz max switching capability, and precise 5 V ±1% internal reference for stable feedback loop design.

Technical Context

The UC3844ADTRG4 implements peak-current-mode (PCM) control with an internal error amplifier (80 dB open-loop gain, 1 MHz unity-gain bandwidth), pulse-by-pulse current limiting via ISENSE input clamped at 1 V, and a precision oscillator programmed by RT/CT with trimmed 8.3 mA discharge current enabling accurate duty-cycle control up to 50%.

Its undervoltage lockout (UVLO) has 16 V turn-on and 10 V turn-off thresholds with hysteresis, ensuring clean startup in AC/DC applications; during UVLO, the OUTPUT pin sinks ≥10 mA at <1.2 V, actively holding external MOSFETs off to prevent parasitic turn-on from Miller effect.

Key Specifications

Pinout & Package

UC3844ADTRG4 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 PCB layouts.

Key Features

Applications

Equivalent & Alternatives

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

Compared with UC3844DTR and SG3844N, UC3844ADTRG4 delivers superior oscillator timing stability due to factory-trimmed 8.3 mA discharge current, tighter 5 V reference (±1% vs ±2%), and higher ESD immunity - making it preferred for high-reliability industrial and medical power supplies where long-term parametric consistency matters.

Availability

UC3844ADTRG4 is available at Aetrix Electronics and suitable for industrial switch-mode PSUs, universal-input flyback converters, and battery-operated power supplies requiring stable component supply, long-lifecycle support, and traceable sourcing.

Supply support for UC3844ADTRG4 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 and embedded processing technologies, with leadership in power management ICs since the 1970s.

The UC384x family was developed specifically for cost-sensitive, high-volume current-mode switch-mode power supplies - targeting off-line AC/DC adapters, industrial PSUs, and DC-DC converters needing robust, integrated PWM control.

FAQ

What is the UVLO threshold of UC3844ADTRG4?

The UC3844ADTRG4 features an undervoltage lockout with a turn-on threshold of 16 V and turn-off threshold of 10 V, providing 6 V hysteresis. This ensures reliable startup from rectified AC lines and prevents oscillatory behavior during brownout conditions. The specification is guaranteed across the device's operating temperature range of 0°C to 70°C.

Does UC3844ADTRG4 support 100% duty cycle operation?

No, UC3844ADTRG4 is limited to ≤50% maximum duty cycle, as confirmed in the Electrical Characteristics table and Device Comparison Table. This is inherent to the UC3844A variant's internal architecture and distinguishes it from UC3842A/UC3843A variants, which support up to 100%. Designers must select appropriate topology (e.g., flyback, forward) compatible with this constraint.

What package type is used for UC3844ADTRG4?

UC3844ADTRG4 is supplied in an 8-pin SOIC (D) package measuring 4.90 mm × 6.00 mm. This surface-mount outline is distinct from PDIP-8 and LCCC-20 variants in the UCx84xA family and is optimized for automated assembly and thermal performance in compact power supply layouts.

How does the oscillator timing work on UC3844ADTRG4?

The UC3844ADTRG4 oscillator frequency and maximum duty cycle are set by external RT (timing resistor) and CT (timing capacitor) connected to the RT/CT pin. With a factory-trimmed 8.3 mA discharge current, the oscillator achieves high timing accuracy - for example, RT = 10 kΩ and CT = 3.3 nF yields ~65 kHz operation. TI recommends RT between 5 kΩ and 100 kΩ, and CT between 470 pF and 4.7 nF.

Can UC3844ADTRG4 drive a MOSFET directly?

Yes, UC3844ADTRG4 integrates a ±1 A totem-pole gate driver on the OUTPUT pin, enabling direct connection to medium-power MOSFET gates. Its low saturation voltage (<0.4 V at 20 mA sink) and fast rise/fall times (25–150 ns into 1 nF) reduce switching losses. A series gate resistor is still required to control dV/dt and suppress ringing, per standard power design practice.