STMicroelectronics STSR30D

Overview

STSR30D from STMicroelectronics is a synchronous rectifier smart driver IC designed for secondary-side gate control in low-voltage, high-efficiency flyback converters. It provides 1.5A peak source/sink gate drive, operates from 4V–5.5V supply, supports 20–500kHz switching, features 700ns inhibit blanking time, and implements cycle-by-cycle anticipation logic to prevent shoot-through during primary switch transitions.

For engineers reviewing the STSR30D datasheet, STSR30D pinout, STSR30D application, or STSR30D equivalent, key selection considerations include its programmable turn-off anticipation (150–300ns), INHIBIT-based discontinuous-mode detection, DISABLE-controlled no-load shutdown, and SO-8 isolation between SGLGND and PWRGND for noise-immune operation in compact AC/DC adapters.

Technical Context

The STSR30D uses a 15MHz internal oscillator synchronized to the CK input to generate precise dead-time-controlled gate signals, with turn-off anticipation dynamically set via voltage division on SETANT (0–VCC). Its fast cycle-by-cycle logic detects primary-side transitions and anticipates synchronous MOSFET turn-off before the clock edge to eliminate secondary-side cross-conduction.

INHIBIT monitors synchronous FET drain voltage to force OUTGATE high when reverse current is detected, enabling safe discontinuous conduction mode; the 700ns blanking window rejects ringing-induced false triggers. DISABLE pin reduces quiescent current to ≤50µA in no-load conditions while maintaining full functionality upon re-enable.

Key Specifications

Pinout & Package

STSR30D is housed in an SO-8 package with fully isolated signal (SGLGND) and power (PWRGND) ground planes to prevent noise coupling into timing logic.

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 UCC24612-2QDRQ1, STSR30D uniquely combines programmable anticipation, dedicated INHIBIT-based DCM handling with blanking, and galvanically isolated grounds-making it optimal for cost-sensitive, space-constrained consumer flyback adapters where layout variability demands tunable timing and noise immunity.

Availability

STSR30D is available at Aetrix Electronics and suitable for USB-C PD adapters, smartphone wall chargers, laptop power supplies, and energy-efficient LED drivers requiring stable component supply, consistent parametric performance, and long-term production continuity.

Supply support for STSR30D 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 manufacturing in Europe and Asia.

The STSR30D belongs to ST's high-efficiency power conversion portfolio, engineered specifically for synchronous rectification in isolated flyback converters targeting consumer and industrial AC/DC applications below 100W.

FAQ

What is the purpose of the SGLGND and PWRGND separation in STSR30D?

SGLGND serves as the reference for all timing, logic, and threshold circuits-including CK, INHIBIT, and SETANT-while PWRGND carries high di/dt gate drive return current. This physical separation prevents switching noise from corrupting sensitive analog comparators and oscillator synchronization, ensuring reliable operation in noisy flyback secondary environments.

How does the INHIBIT function enable discontinuous conduction mode (DCM)?

INHIBIT monitors the synchronous FET's drain-source voltage; when reverse current flows, the voltage drops below −25mV, triggering OUTGATE to go high and blocking conduction. The 700ns blanking window ignores transient ringing during primary turn-off, allowing clean DCM detection without external components or auxiliary windings.

Can STSR30D operate without the SETANT external resistor divider?

No. SETANT must be connected to a resistor divider between VCC and GND to select one of three fixed anticipation times (150/225/300ns). Leaving SETANT floating or shorted causes undefined timing behavior; the internal leakage current specification (±0.1µA) confirms it is not a high-impedance reference node but an active voltage-sensing input.

What is the minimum recommended CK signal amplitude for reliable synchronization?

The CK input has guaranteed thresholds of 1.2V (rising) and 0.8V (falling). To ensure noise margin and reliable edge detection, the CK signal should exceed 2.0V peak-to-peak with fast edges (<100ns). Transformer-coupled CK signals must be clamped and limited to ≤VCC+0.3V using external diodes (e.g., D2 in Figure 2) to prevent absolute maximum rating violation.