Texas Instruments UCD7138DRST

Overview

UCD7138DRST from Texas Instruments is a 4-A source / 6-A sink single-channel low-side synchronous rectifier (SR) driver with body-diode conduction sensing and reporting, designed for use with UCD3138A digital PWM controllers in isolated DC-DC converters. It delivers rail-to-rail gate drive, detects body-diode conduction as low as 10 ns using a –150-mV threshold comparator, and enables dead-time optimization for LLC and full-bridge topologies.

For engineers reviewing the UCD7138DRST datasheet, UCD7138DRST pinout, UCD7138DRST application, or UCD7138DRST equivalent, this page provides verified technical context, confirmed pin functions, real-world efficiency impact data, and validated alternative options for SR driver selection in high-efficiency digital power systems.

Technical Context

The UCD7138DRST implements asymmetrical gate drive (4-A peak source, 6-A peak sink) with 5-ns typical rise/fall times and 14-ns typical propagation delays, enabling stable operation up to 2 MHz. Its internal –150-mV body-diode conduction detector feeds real-time DTC signals to the UCD3138A controller for dynamic dead-time adjustment.

Turnon edge optimization is controlled via the CTRL pin (enabled when floating or at 3.3 V), while turnoff is strictly IN-pin–driven. The device integrates UVLO (3.8-V turnon, 240-mV hysteresis), thermal pad–enhanced WSON-6 packaging, and noise-immune blanking logic that suppresses DTC output during OUT-high periods.

Key Specifications

Pinout & Package

UCD7138DRST uses a 6-pin 3.00 mm × 3.00 mm WSON package with exposed thermal pad (GND). The compact footprint minimizes parasitic inductance for high-speed gate driving and improves thermal dissipation in high-current SR applications.

Key Features

Applications

Equivalent & Alternatives

The following parts are listed as comparable options for similar synchronous rectifier driver applications.

Compared with LM5109BMAX/NOPB and UCC27531DRSAR, the UCD7138DRST uniquely integrates body-diode conduction sensing, DTC reporting, and turnon-edge optimization-enabling closed-loop SR timing control without external components or firmware overhead in UCD3138A-based systems.

Availability

UCD7138DRST is available at Aetrix Electronics and suitable for LLC resonant converters, hard-switching full-bridge power supplies, and digital power-control applications requiring stable component supply, long-term lifecycle support, and traceable sourcing.

Supply support for UCD7138DRST 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 focused on analog and embedded processing technologies, with leadership in power management, signal chain, and microcontrollers.

The UCD7138DRST belongs to TI's UCD digital power controller companion IC family, engineered specifically to extend the capabilities of UCD3138A-based systems by adding hardware-accelerated synchronous rectification control with minimal latency and high noise immunity.

FAQ

What is the primary function of the UCD7138DRST in a power converter?

The UCD7138DRST is a dedicated low-side synchronous rectifier driver that senses MOSFET body-diode conduction via its VD pin and reports timing-critical events on the DTC pin to the UCD3138A controller. This enables real-time dead-time optimization, reducing conduction losses in isolated DC-DC topologies like LLC and full-bridge converters. Its 4-A source / 6-A sink drive strength and 5-ns rise time ensure fast, efficient gate switching in high-frequency designs.

How does the UCD7138DRST interface with the UCD3138A digital controller?

The UCD7138DRST interfaces with the UCD3138A through three key pins: IN receives DPWM output signals to trigger gate drive; DTC sends body-diode conduction status as a digital pulse to UCD3138A's DTC0/DTC1 inputs; and CTRL enables or disables turnon-edge optimization based on controller configuration. This tightly coupled hardware interface eliminates software polling or ADC sampling, reducing latency and improving timing accuracy in dynamic load conditions.

What is the significance of the –150-mV body-diode conduction threshold in the UCD7138DRST?

The –150-mV threshold on the VD pin allows the UCD7138DRST to reliably detect MOSFET body-diode conduction even under high dV/dt conditions common in resonant converters. This precise, low-offset sensing enables accurate measurement of conduction duration down to 10 ns-critical for optimizing dead time in LLC topologies where conduction timing varies significantly with load and line conditions. The threshold is factory-trimmed and stable over temperature (±13 mV variation from –40°C to 125°C).

Can the UCD7138DRST operate independently of the UCD3138A controller?

No-the UCD7138DRST is designed exclusively as a companion IC to the UCD3138A and related UCD digital power controllers. Its DTC reporting, turnon-edge optimization logic, and timing-critical response rely on synchronized DPWM signals and controller-level dead-time management. While it powers up and drives gates based on IN input alone, full functionality-including body-diode–driven turnon acceleration and system-level efficiency gains-requires integration with the UCD3138A chipset.

What package type and thermal characteristics does the UCD7138DRST use?

The UCD7138DRST uses a 6-pin WSON package (DRS) measuring 3.00 mm × 3.00 mm with an exposed thermal pad (GND). Its junction-to-board thermal resistance (R_θJB) is 46.3°C/W, and junction-to-ambient (R_θJA) is 73.4°C/W-enabling reliable operation at 125°C junction temperature under typical PCB layout conditions with 2 oz copper and thermal vias. The thermal pad must be soldered to a solid GND plane for optimal performance.