Texas Instruments UCC2804D

Overview

UCC2804D from Texas Instruments is a low-power BiCMOS current-mode PWM controller for off-line power supplies, featuring 50% maximum duty cycle, 12.5 V UVLO turn-on threshold, 5 V reference voltage with ±1.5% tolerance, and 70 ns current-sense-to-output response. It integrates internal soft start, leading-edge blanking, and totem-pole gate drive capable of ±750 mA peak output - optimized for high-reliability AC/DC adapters and industrial PSU designs.

For engineers reviewing the UCC2804D datasheet, UCC2804D pinout, UCC2804D application, or UCC2804D equivalent, key selection criteria include its 50% duty cycle limit (vs. 100% in UCC2802), higher UVLO hysteresis (4.2 V), compatibility with UC3842A pinout, and operation across –40°C to 125°C without external soft-start components.

Technical Context

The UCC2804D implements fixed-frequency current-mode control using an internal oscillator with RC timing (REF→RC resistor, RC→GND capacitor), delivering up to 1 MHz switching. Its dual current-sense comparators - one for PWM regulation and one for overcurrent fault detection - are digitally blanked for 100 ns after each OUT rising edge, eliminating need for external RC filtering on the CS pin.

It features a true low-impedance 2-MHz error amplifier at COMP (capable of sourcing/sinking current), internal full-cycle soft start clamping COMP voltage to 5 V over 4–10 ms, and a 5-V reference (REF) stable over temperature and load. The device enters UVLO below 8.3 V and restarts only after VCC exceeds 12.5 V, ensuring clean power-up sequencing in offline converters.

Key Specifications

Pinout & Package

UCC2804D is housed in an 8-pin SOIC (D package), 3.91 mm × 4.90 mm body size, with Gull-wing leads and standard JEDEC MS-012AC footprint. Thermal resistance R_θJA = 117.9°C/W enables >0.65 W dissipation at TA = 25°C with minimal heatsinking.

Key Features

Applications

Equivalent & Alternatives

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

Compared with UCC2802D and UC3842AD, the UCC2804D uniquely balances high-voltage robustness (12.5 V UVLO), fault resilience (digital blanking), and low-power operation (500 μA I_CC) - making it optimal for space-constrained, thermally demanding flyback converters where duty-cycle limiting is essential.

Availability

UCC2804D is available at Aetrix Electronics and suitable for AC/DC adapters, industrial flyback PSUs, and automotive battery chargers requiring stable component supply, long-term lifecycle support, and AEC-Q100-aligned reliability.

Supply support for UCC2804D 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 specializing in analog, embedded processing, and power management ICs, with decades of expertise in power conversion architecture and high-reliability manufacturing.

The UCC280x family was designed specifically for high-efficiency, low-component-count current-mode switching power supplies - targeting offline and DC/DC applications where startup current, thermal performance, and fault immunity are critical.

FAQ

What is the maximum operating frequency of the UCC2804D?

The UCC2804D supports oscillator frequencies up to 1 MHz, determined by the RC timing network (REF → RC resistor, RC → GND capacitor). For UCC2804D, the formula is f ≈ 1.5/(R × C), with recommended R = 10 kΩ–200 kΩ and C = 100 pF–1000 pF. At 1 MHz, propagation delays remain stable and CS blanking maintains noise immunity.

Does the UCC2804D require an external soft-start circuit?

No - the UCC2804D integrates full-cycle internal soft start that clamps the COMP voltage to ramp linearly to 5 V over 4–10 ms. This eliminates the need for external resistors, capacitors, and PNP transistors traditionally used with UC3842-family controllers, reducing BOM count and board area.

How does the UCC2804D differ from the UC3842A in current-sense handling?

The UCC2804D features digital leading-edge blanking - disconnecting the CS pin from both PWM and overcurrent comparators for 100 ns after each OUT rising edge. Unlike UC3842A, which requires external RC filtering to suppress gate-drive noise, UCC2804D achieves cleaner sensing with no added components and lower CS-to-OUT delay (70 ns vs. ~200 ns).

What is the purpose of the 4.2 V UVLO hysteresis in the UCC2804D?

The 4.2 V hysteresis (12.5 V turn-on, 8.3 V turn-off) prevents oscillatory restart during brownout conditions common in industrial mains or automotive battery systems. This wide gap ensures the UCC2804D remains latched off until VCC recovers sufficiently - avoiding repeated stress on the power MOSFET and output rectifier during unstable input.

Can the UCC2804D drive a MOSFET directly without a gate driver IC?

Yes - the UCC2804D's totem-pole output delivers ±750 mA peak current, sufficient to drive MOSFETs with gate charge (Qg) ≤ 20 nC at switching frequencies up to 500 kHz. For higher Qg devices or >1 MHz operation, a discrete buffer may be added, but most 600 V/1 A–5 A MOSFETs interface directly with robust rise/fall times (41 ns/44 ns into 1 nF).