STMicroelectronics STSR3CD-TR

Overview

STSR3CD-TR from STMicroelectronics is a synchronous rectifier smart driver IC designed for secondary-side gate control in low-voltage, high-efficiency flyback converters. It delivers 2A source / 3.5A sink peak output current, operates from 4V–5.5V supply, supports 30–750kHz clock input, implements smart turn-off anticipation (75–225ns), and features automatic duty-cycle shutdown below 14%. It prevents shoot-through by anticipating primary switch turn-on.

For engineers reviewing the STSR3CD-TR datasheet, STSR3CD-TR pinout, STSR3CD-TR application, or STSR3CD-TR equivalent, this page provides verified functional context, SO-8 package mapping, timing-critical design parameters, and real-world flyback converter integration guidance - all grounded in ST's 2003 official specification.

Technical Context

The STSR3CD-TR uses a 15MHz internal oscillator synchronized to an external clock (CK) to generate cycle-by-cycle gate drive with programmable turn-off anticipation. Its digital control logic enforces dead-time safety by preemptively disabling OUTGATE before primary-side transitions, avoiding secondary-side shoot-through.

It integrates separate signal ground (SGLGND) and power ground (PWRGND), UVLO (V_CCON = 4V, V_CCOFF = 3.6V), and an inhibit comparator with –25mV threshold to force discontinuous conduction mode when reverse current is detected at the synchronous MOSFET.

Key Specifications

Pinout & Package

STSR3CD-TR is housed in an SO-8 surface-mount package (5.0mm × 4.0mm, 1.27mm pitch) with exposed thermal pad per ST's mechanical drawing 0016023/C. The package supports 160°C/W junction-to-ambient thermal resistance on single-layer PCBs.

Key Features

Applications

Equivalent & Alternatives

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

Compared with MP6908DJ-LF-Z and NCP4303ADR2G, STSR3CD-TR uniquely combines programmable anticipation, dual-ground isolation, and deterministic DCM entry via analog INHIBIT threshold - making it the preferred choice for robust, transformer-coupled flyback designs where timing predictability and EMI control are critical.

Availability

STSR3CD-TR is available at Aetrix Electronics and suitable for AC/DC adapters, USB PD chargers, industrial 24V flybacks, and medical auxiliary supplies requiring stable component supply and long-term production continuity.

Supply support for STSR3CD-TR 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

STMicroelectronics is a global semiconductor leader headquartered in Geneva, Switzerland, specializing in power management, analog, microcontrollers, and automotive ICs with vertical manufacturing and broad distribution.

The STSR3 product line targets high-efficiency isolated DC/DC conversion, specifically addressing timing-critical synchronous rectification in flyback topologies where shoot-through prevention and DCM flexibility are essential.

FAQ

What is the purpose of the SGLGND and PWRGND separation?

SGLGND serves as the reference for all internal comparators, oscillators, and digital logic, while PWRGND carries high di/dt gate drive return currents. This physical separation prevents ground bounce from corrupting timing decisions - especially critical for accurate anticipation and INHIBIT threshold detection in noisy power environments.

How is turn-off anticipation time selected on STSR3CD-TR?

Anticipation time (t_ANT) is set by applying one of three voltage levels to the SETANT pin: 0–1/3V_CC → 75ns, 1/3–2/3V_CC → 150ns, or 2/3–V_CC → 225ns. This is implemented using a resistor divider from VCC to GND, allowing precise matching to transformer propagation delay and MOSFET turn-off characteristics.

Can STSR3CD-TR operate without an external clock signal?

No - STSR3CD-TR requires a valid clock input on the CK pin to synchronize its internal 15MHz oscillator and generate gate drive timing. It has no internal free-running oscillator; missing or invalid CK signal results in no OUTGATE activity and automatic duty-cycle shutdown after 14% threshold violation.

What protection features does STSR3CD-TR include?

STSR3CD-TR integrates under-voltage lockout (UVLO), shoot-through prevention via programmable anticipation, automatic duty-cycle shutdown below 14%, reverse-current detection via INHIBIT comparator, and absolute maximum ratings protection on all pins (e.g., ±1kV ESD on most pins, 10mA current-limited CK/INHIBIT inputs).