Texas Instruments UC2901D

Overview

UC2901D from Texas Instruments is an isolated feedback generator IC designed for closed-loop regulation across voltage isolation boundaries in switch-mode power supplies. It implements amplitude modulation using an internal 130–170 kHz oscillator, integrates a 1.5 V ±1% reference and high-gain error amplifier, and delivers dual driver outputs (DRIVERA/DRIVERB) with ±1.6 V swing and 15 mA source capability - enabling transformer-coupled or capacitor-coupled feedback in AC-DC and DC-DC converters.

For engineers reviewing the UC2901D datasheet, UC2901D pinout, UC2901D application, or UC2901D equivalent, key selection considerations include its –40°C to +85°C operating range, SOIC-14 package, UVLO threshold at 3.9–4.5 V, STATUS output active-low monitoring of ±150 mV input window, and compatibility with external clock synchronization up to 5 MHz.

Technical Context

The UC2901D uses an internal amplitude-modulation architecture where the error amplifier's compensation terminal (Pin 12) drives a modulator whose output is buffered by two emitter-follower drivers. The carrier frequency is set by RT/CT or synchronized externally via Pin 2, supporting fixed 50% duty cycle operation when using the internal oscillator.

Its error amplifier features 60 dB CMRR, 100 dB PSRR, and 60 dB open-loop gain, with input offset voltage ≤4 mV and bias current ≤–3 µA. The STATUS output asserts low when the differential error voltage falls within ±150 mV of the 1.5 V reference, providing real-time loop integrity indication without additional circuitry.

Key Specifications

Pinout & Package

UC2901D is housed in a 14-pin SOIC (D package), 3.9 mm width, RoHS-compliant with CU NIPDAU finish and JEDEC MSL Level-2-260°C-1 year rating.

Key Features

Applications

Equivalent & Alternatives

The following parts are listed as comparable options for similar isolated feedback generator applications.

Compared with UC3901D, UC2901D extends operational temperature to –40°C and tightens oscillator initial accuracy; compared with LM5018, UC2901D provides dedicated isolated feedback generation with status monitoring but requires external PWM controller and power stage.

Availability

UC2901D is available at Aetrix Electronics and suitable for AC-DC adapters, isolated DC-DC converters, medical power supplies, and telecom rectifier modules requiring stable component supply, long-term manufacturability, and RoHS-compliant packaging.

Supply support for UC2901D 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 headquartered in Dallas, Texas, delivering analog and embedded processing solutions across industrial, automotive, and personal electronics markets.

The UC2901D belongs to TI's UCx901 family of isolated feedback generators, engineered specifically to replace optocouplers in regulated power supplies by enabling reliable, low-cost, transformer-based error signal transmission.

FAQ

What is the primary function of the UC2901D in a power supply design?

The UC2901D functions as an isolated feedback generator that transmits error signals across voltage barriers using amplitude modulation. It replaces optocouplers in switch-mode power supplies by driving small RF transformers or capacitors with modulated driver outputs. Its integrated 1.5 V reference, error amplifier, and STATUS monitor allow precise regulation and loop integrity verification - all implemented within the UC2901D without external precision components.

Does the UC2901D require external components to operate, and which ones are mandatory?

Yes, the UC2901D requires external components for basic operation: RT and CT resistors/capacitors to set oscillator frequency (or an external clock source at Pin 2), a feedback network between Pins 5 (EA–), 6 (EA+), and 7 (COMP), and pull-up resistors on DRIVERA/DRIVERB outputs if driving transformer primaries. The STATUS output requires a pull-up resistor. No external reference or error amplifier is needed - these are fully integrated inside the UC2901D.

How does the STATUS output of the UC2901D behave under normal regulation and fault conditions?

The STATUS output of the UC2901D is an active-low open-collector indicator that asserts low when the differential voltage between EA+ and EA– is within ±150 mV of the 1.5 V reference - confirming proper closed-loop operation. It remains high during startup, overload, or open-loop faults. This behavior is intrinsic to the UC2901D's internal comparator and requires no external logic; it can directly interface with PWM controller FAULT pins or microcontroller GPIOs.

Can the UC2901D be used with an external clock, and what are the timing constraints?

Yes, the UC2901D supports external clock synchronization via Pin 2 (CLK). To enable this mode, Pin 1 (CR) must be tied to VIN to disable the internal oscillator. The UC2901D accepts TTL- or CMOS-level clocks up to 5 MHz, with defined thresholds of 0.5 V (low) and 1.6 V (high). The external clock directly controls DRIVERA/DRIVERB frequency and duty cycle - making the UC2901D suitable for synchronous SMPS designs where EMI reduction is critical.

What is the significance of the "D" suffix in UC2901D, and how does it differ from UC2901J or UC2901Q?

The "D" suffix in UC2901D denotes the SOIC-14 surface-mount package (JEDEC MS-012), distinct from UC2901J (CDIP-14) and UC2901Q (PLCC-20). All share identical electrical functionality and temperature grading (–40°C to +85°C), but differ in mounting method, thermal resistance, and board space. The UC2901D is optimized for automated assembly and compact layouts, with CU NIPDAU lead finish and MSL Level-2 moisture sensitivity - confirmed in TI's official packaging addendum for UC2901DTRG4.