Texas Instruments UCD3138RMHT

Overview

UCD3138RMHT from Texas Instruments is a highly integrated digital power controller for isolated DC-DC and AC-DC converters, featuring three independent hardware PID-based feedback loops, 250-ps DPWM resolution, 16-MHz EADC with 1-mV/LSB configurable resolution, and a 31.25-MHz ARM7TDMI-S processor with 32 KB flash. It supports phase-shifted full bridge, LLC, and PFC topologies in telecom rectifiers and server power supplies.

For engineers reviewing the UCD3138RMHT datasheet, UCD3138RMHT pinout, UCD3138RMHT application, or UCD3138RMHT equivalent, key selection criteria include DPWM timing precision (4-ns frequency/phase resolution), dual-mode current sensing (copper trace + primary-side voltage), burst mode and ideal diode emulation for light-load efficiency, and PMBus/I²C programmability for closed-loop telemetry and firmware updates.

Technical Context

The UCD3138RMHT implements three Digital Power Peripherals (DPPs), each integrating a dedicated 16-MHz EADC, 2-pole/2-zero PID compensator, and high-resolution DPWM outputs-enabling simultaneous voltage, current, and constant-power regulation without CPU intervention. Its front-end architecture supports peak/average current mode, voltage mode, and nonlinear control via hardware-configurable comparators and dithering.

It combines a 31.25-MHz ARM7TDMI-S core executing real-time system management with 14-channel 12-bit 267-ksps ADC, 7 high-speed analog comparators with cycle-by-cycle limiting, and synchronized multi-device operation via SYNC IN/OUT pins-optimized for high-density, thermally constrained isolated power modules requiring deterministic sub-100-ns timing control.

Key Specifications

Pinout & Package

UCD3138RMHT is housed in a 40-pin WQFN package (6.00 mm × 6.00 mm) with exposed thermal pad, optimized for high-power density and thermal performance in compact isolated power modules. Pin count and layout match the RHA/RJA variants but feature corner anchor pins for enhanced mechanical reliability.

Key Features

Applications

Equivalent & Alternatives

The following parts are listed as comparable options for similar digital power controller applications.

Compared with UCD3138RMHT, the RHA offers identical digital power features but inferior thermal cycling endurance, while the RJA delivers identical performance with validated board-level reliability-making it the preferred choice for production programs demanding lifecycle assurance.

Availability

UCD3138RMHT is available at Aetrix Electronics and suitable for telecom rectifiers, server PSUs, and isolated DC-DC modules requiring stable component supply, long-term lifecycle support, and consistent parametric performance across manufacturing lots.

Supply support for UCD3138RMHT 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 50 years of innovation in high-reliability power conversion solutions.

The UCD3138 product line was designed specifically for digitally controlled isolated power supplies-emphasizing hardware-accelerated loop control, multi-topology flexibility, and seamless integration with TI's Fusion Digital Power ecosystem.

FAQ

What is the maximum DPWM switching frequency supported by the UCD3138RMHT?

The UCD3138RMHT supports DPWM switching frequencies up to 2 MHz. This capability is enabled by its 250-ps pulse-width resolution and 4-ns frequency resolution, allowing precise timing control essential for high-frequency LLC and phase-shifted full-bridge topologies. The UCD3138RMHT maintains full hardware-based loop control and fault protection even at maximum switching frequency.

Does the UCD3138RMHT support peak current mode control?

Yes, the UCD3138RMHT supports peak current mode control using EADC2 (EAP2/EAN2) as the dedicated front-end for current-sense signal conditioning. This channel includes hardware-based blanking, slope compensation, and cycle-by-cycle limiting-fully implemented in analog/digital hardware without ARM core involvement. Peak current mode is explicitly validated for PSFB and hard-switched topologies per TI's UCD3138 Family Practical Design Guidelines.

How many independent feedback loops does the UCD3138RMHT implement in hardware?

The UCD3138RMHT implements three independent, fully hardware-based feedback loops-each with its own dedicated Error ADC, 2-pole/2-zero PID compensator, and associated DPWM outputs. These loops operate autonomously and concurrently, supporting mixed-mode regulation such as voltage + current + constant power, with no CPU overhead or scheduling latency affecting loop stability.

What communication interfaces are available on the UCD3138RMHT?

The UCD3138RMHT provides PMBus/I²C and one UART (SCI) interface. PMBus supports full SBS-compliant telemetry-including READ_VOUT, VOUT_COMMAND, and MFR_SPECIFIC commands-while the UART enables firmware updates, debug logging, and custom protocol implementation. No SPI or second UART is present on the RMH variant, distinguishing it from the 64-pin RGC version.

Is the UCD3138RMHT pin-compatible with other UCD3138 package variants?

The UCD3138RMHT shares identical pin functions and assignments with the UCD3138RHA and UCD3138RJA 40-pin variants-enabling direct PCB footprint reuse. However, the RMH uses a WQFN package with corner anchor pins and thinner profile, whereas RJA uses VQFN with thicker body and optimized BLR performance. TI explicitly recommends RJA-not RMH-for new designs due to reliability validation.