Texas Instruments UC3907N

Overview

UC3907N from Texas Instruments is a load share controller IC designed for parallel power module current balancing in high-reliability DC-DC systems. It provides fully differential high-impedance voltage sensing (±1.25% reference accuracy), a 20 V/V fixed-gain current amplifier, optocoupler driving capability (up to 20 mA), and master-status indication - enabling precise current sharing within ±2.5% across paralleled modules in telecom and industrial power supplies.

For engineers reviewing the UC3907N datasheet, UC3907N pinout, UC3907N application, or UC3907N equivalent, key selection criteria include its 4.5–35 V supply range, DIP-16 package with validated 16-pin terminal mapping, differential current-sense architecture, and compatibility with both isolated (optocoupler) and direct-coupled feedback topologies in redundant power systems.

Technical Context

The UC3907N implements a dual-loop control architecture: a voltage error amplifier (pins 11/12) regulates output voltage via adjustable reference, while an independent transconductance adjust amplifier (pins 13–15) compares local current sense to a shared bus signal to dynamically trim the reference by up to ±100 mV (±5%). Its buffer amplifier (pins 1/15) drives the low-impedance current-share bus unidirectionally, ensuring only the highest-current module acts as master.

Each functional block operates referenced to (–) SENSE (pin 4), with Artificial GND (pin 6) held at +250 mV above it to enable rail-to-rail biasing. The current amplifier accepts common-mode inputs from 0 V to V_CC–2 V, supporting shunt placement on either side of power return, and features 60 dB PSRR and 0.4 V/µs slew rate for noise-immune operation in high-dV/dt environments.

Key Specifications

Pinout & Package

Dual-in-line package (PDIP-16, N suffix), 0.3-inch body width, through-hole mounting. Pin 1 index located at top-left corner (notch or dot); pin numbering counterclockwise.

Key Features

Applications

Equivalent & Alternatives

The following parts are listed as comparable options for similar load-sharing controller applications.

Compared with UC2907N, UC3907N offers lower cost and tighter production binning for commercial temperature grade, while LTC4370 provides higher precision at the expense of increased design complexity and loss of master-status signaling - making UC3907N the optimal choice for established telecom and server PSU platforms requiring proven reliability and minimal layout changes.

Availability

UC3907N is available at Aetrix Electronics and suitable for telecom rectifier modules, industrial redundant PSUs, and server intermediate bus converters requiring stable component supply across multi-year production cycles.

Supply support for UC3907N 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 technologies, with over 90 years of innovation in high-reliability electronic components.

The UCx907 family was developed specifically for analog current-sharing control in paralleled DC-DC power modules, targeting applications where digital controllers introduce latency, complexity, or certification overhead.

FAQ

What is the primary function of the UC3907N in a power system?

The UC3907N serves as an analog load share controller that enables multiple independent DC-DC power modules to operate in parallel with precise current balancing. It achieves this by monitoring each module's output current via a differential sense amplifier, comparing it to a shared bus signal, and dynamically adjusting the module's voltage reference to force equal current distribution - all without digital communication or microcontroller intervention. This function is core to the UC3907N's architecture and defines its role in redundant power architectures.

Can the UC3907N be used with non-isolated power topologies?

Yes, the UC3907N supports both isolated and non-isolated configurations. In non-isolated designs, the DRIVE amplifier output (pin 9) can deliver a 0.25–4.1 V voltage signal directly to the PWM controller's feedback node, though polarity inversion may be required. The UC3907N's voltage amplifier (pins 11/12) and adjust amplifier (pins 13–15) operate independently of isolation method, making it adaptable to buck, boost, or linear regulator implementations - a key flexibility built into the UC3907N's analog-centric design.

What does the STATUS INDICATE pin (pin 16) indicate, and how is it used?

The STATUS INDICATE pin (pin 16) is an open-collector output that pulls low exclusively when the UC3907N is acting as the master module in a paralleled configuration. It is driven by internal logic that detects the low-state output of the adjust amplifier - which occurs only in the master unit due to its 50 mV internal offset. This signal enables external hardware (e.g., LED indicators, FPGA inputs, or supervisor ICs) to identify the master for diagnostics, thermal derating, or graceful failover - a deterministic behavior confirmed in UC3907N's functional description and pin assignments.

How does the UC3907N handle fault conditions like an open or shorted current-share bus?

The UC3907N maintains safe operation during current-share bus faults: if the bus opens, all modules default to independent regulation with no reference adjustment; if shorted to ground, the buffer amplifier (pin 1) presents 10 kΩ impedance, preventing damage while allowing normal voltage regulation. The UC3907N's architecture explicitly guarantees continued functionality under these conditions - as stated in its description - because the voltage error amplifier loop remains fully operational regardless of bus state, ensuring uninterrupted power delivery.

Is the UC3907N pin-compatible with other members of the UCx907 family?

Yes, the UC3907N is fully pin-compatible with UC1907N and UC2907N across all package variants (PDIP-16 and SOIC-16), sharing identical pin functions, electrical characteristics, and block diagram architecture. Differences are limited to temperature grade (UC3907N: 0°C–70°C; UC2907N: –40°C–85°C; UC1907N: –55°C–125°C) and minor parameter tolerances - allowing direct substitution in existing layouts when environmental requirements permit. This compatibility is documented in TI's SLUS165C datasheet and packaging addendum.