Texas Instruments UCD7138DRSR

Overview

UCD7138DRSR from Texas Instruments is a 4-A source / 6-A sink single-channel low-side synchronous rectifier (SR) gate driver with body-diode conduction sensing and reporting, designed for use with UCD3138A digital PWM controllers in isolated DC-DC converters. It features –150-mV body-diode detection threshold, 14-ns typical propagation delay, 5-ns typical rise/fall times, and operates from 4.5 V to 18 V supply. It enables dead-time optimization in high-efficiency LLC and full-bridge topologies.

For engineers reviewing the UCD7138DRSR datasheet, UCD7138DRSR pinout, UCD7138DRSR application, or UCD7138DRSR equivalent, key selection criteria include body-diode conduction reporting latency (<23 ns), rail-to-rail drive capability, DTC interface compatibility with UCD3138A, thermal pad grounding, and WSON-6 package layout constraints.

Technical Context

The UCD7138DRSR integrates a high-speed comparator with –150-mV threshold for detecting MOSFET body-diode conduction on the VD pin, and reports conduction state via open-drain DTC output. Its gate driver uses asymmetrical pull-up (5 Ω) and pull-down (0.35 Ω) structures to deliver 4-A peak source and 6-A peak sink current, enabling fast switching up to 2 MHz.

Control logic couples IN (DPWM input) and DTC signals to determine OUT timing: when DTC is low at IN's rising edge, OUT turns on immediately; otherwise, OUT waits for DTC assertion. The CTRL pin enables/disables turn-on edge optimization, and internal UVLO (3.8 V turn-on, 240 mV hysteresis) ensures safe startup.

Key Specifications

Pinout & Package

UCD7138DRSR is housed in a thermally enhanced 6-pin WSON package (3.00 mm × 3.00 mm) with an exposed thermal pad (GND). The package supports high-power density layouts and requires soldering the thermal pad to a PCB ground plane for optimal thermal performance (R_θJB = 46.3°C/W).

Key Features

Applications

Equivalent & Alternatives

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

Compared with LM5113SDX/NOPB and UCC27536DR, the UCD7138DRSR uniquely integrates body-diode conduction detection and DTC reporting in a compact WSON-6 package, enabling closed-loop dead-time optimization with UCD3138A-reducing system-level design effort and improving efficiency across operating conditions without external components.

Availability

UCD7138DRSR is available at Aetrix Electronics and suitable for high-efficiency isolated DC-DC converters, digital power-control platforms, and LLC resonant applications requiring stable component supply and long-term production continuity.

Supply support for UCD7138DRSR 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 delivering analog and embedded processing solutions for industrial, automotive, and communications markets.

The UCD7138DRSR belongs to TI's UCD digital power controller companion IC family, designed specifically to extend the capabilities of UCD3138A-based systems by adding intelligent, low-latency synchronous rectification control with minimal external components.

FAQ

What is the function of the CTRL pin on the UCD7138DRSR?

The CTRL pin on the UCD7138DRSR enables or disables gate turn-on edge optimization. When left floating or pulled to logic high (≥3.3 V), it activates immediate OUT assertion upon detection of body-diode conduction at the IN rising edge. When tied to ground, this optimization is disabled and OUT follows IN directly. This behavior is confirmed in the device's truth table (Section 8.3.2) and applies specifically to the UCD7138DRSR's operation with UCD3138A controllers.

How does the UCD7138DRSR interface with the UCD3138A digital controller?

The UCD7138DRSR interfaces with the UCD3138A via three dedicated connections: IN receives DPWM output, DTC reports body-diode conduction status as an open-drain signal to UCD3138A's DTC0/DTC1 pins, and VD connects to the SR MOSFET drain through a 20-Ω resistor. This interface enables the UCD3138A to dynamically adjust dead time based on real-time conduction feedback - a capability verified in UCD7138DRSR's functional block diagram and timing diagrams.

What is the minimum detectable body-diode conduction time for the UCD7138DRSR?

The UCD7138DRSR can detect body-diode conduction events as short as 10 ns, as specified in Section 1 (Features) and confirmed in Section 7.6 (Switching Characteristics) under parameter tw(VD). This value is measured at both VCC = 5 V and 12 V across temperature, and represents the shortest pulse width on the VD pin that reliably changes the DTC output state - a key specification for high-frequency LLC converter operation.

Does the UCD7138DRSR require external components for basic operation?

Yes - the UCD7138DRSR requires a minimum 1-µF ceramic bypass capacitor between VCC and the thermal pad (GND), a 20-Ω resistor between VD and the SR MOSFET drain, and proper grounding of the exposed thermal pad. These are mandatory per Sections 6 (Pin Functions) and 10 (Power Supply Recommendations); omission risks unstable operation, inaccurate sensing, or thermal failure. No external components are needed for DTC reporting or gate drive functionality beyond these.

What is the purpose of the VD pin on the UCD7138DRSR?

The VD pin on the UCD7138DRSR is the drain voltage sense input for the internal –150-mV comparator that detects MOSFET body-diode conduction. It must be connected to the SR MOSFET drain via a 20-Ω series resistor to limit current and ensure accurate threshold detection. The pin has a maximum rating of 45 V and is not intended for direct high-voltage connection - this role is explicitly defined in the Pin Functions table and validated in Figure 24 timing diagrams for the UCD7138DRSR.