STMicroelectronics ST1S09PUR

Overview

ST1S09PUR from STMicroelectronics is a 2 A, 1.5 MHz synchronous step-down DC-DC converter in DFN6 (3 × 3 mm) package, featuring current-mode PWM control, integrated high- and low-side MOSFETs (R_DS(ON) = 100 mΩ each), and ±2 % output voltage tolerance. It operates from 2.7 V to 6 V input and delivers adjustable output down to 0.8 V via external resistor divider, targeting power rails for microcontrollers, FPGAs, and portable logic in space-constrained applications.

For engineers reviewing the ST1S09PUR datasheet, ST1S09PUR pinout, ST1S09PUR application, or ST1S09PUR equivalent, key selection criteria include its 1.5 MHz fixed-frequency operation enabling compact 2.7–3.3 µH inductors, integrated over-voltage protection with 200 ns response, Power Good open-drain flag, and thermal shutdown at 150 °C - all validated for industrial temperature range (−30 °C to 125 °C).

Technical Context

The ST1S09PUR employs constant-frequency current-mode PWM control with cycle-by-cycle current limiting and internal compensation, eliminating need for external loop components. Its dual-supply architecture separates analog (VIN_A) and switch (VIN_SW) rails to reduce noise coupling and improve regulation stability under dynamic load.

It integrates both NMOS and PMOS power switches with matched 100 mΩ R_DS(ON), enabling synchronous rectification and >90 % typical efficiency at 2 A. The feedback pin (FB) references 800 mV with ±16 mV tolerance, and the Power Good (PG) output asserts high when V_OUT ≥ 0.92 × V_NOM.

Key Specifications

Pinout & Package

ST1S09PUR is housed in a thermally enhanced DFN6 (3 × 3 mm) package with exposed pad tied to GND for optimal electrical and thermal performance. The 6-pin top-side layout supports high-density routing and efficient heat transfer to PCB ground plane.

Key Features

Applications

Equivalent & Alternatives

The following parts are listed as comparable options for similar synchronous buck regulator applications.

Compared with TPS62130ARGTR and MP2143GJ-Z, ST1S09PUR uniquely combines dual supply rails (VIN_A/VIN_SW), 800 mV FB reference for sub-1.2 V outputs, and configurable INH/PG pin - making it optimal for noise-sensitive, multi-rail embedded systems where layout simplicity and analog integrity are prioritized over maximum switching frequency.

Availability

ST1S09PUR is available at Aetrix Electronics and suitable for portable medical devices, industrial PLCs, USB-powered peripherals, and automotive infotainment subsystems requiring stable component supply, long-term lifecycle support, and RoHS-compliant packaging.

Supply support for ST1S09PUR 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, designing and manufacturing analog, MCU, power, and sensor solutions for industrial, automotive, and consumer markets.

The ST1S09PUR belongs to ST's ST1S series of monolithic synchronous buck regulators, engineered specifically for space-constrained, high-efficiency point-of-load conversion in battery-powered and thermally demanding applications.

FAQ

What is the minimum recommended output capacitor for stable operation?

The ST1S09PUR is characterized with 22 µF output capacitance using X5R/X7R ceramic capacitors. Stable operation requires ≥10 µF total output capacitance with ESR ≤10 mΩ; lower ESR improves transient response and reduces ripple, but values below 10 µF risk instability per Figure 21 application circuit validation.

Can the INH/PG pin be used simultaneously for inhibit and Power Good functions?

No - the INH/PG pin is functionally exclusive: ST1S09PUR variants are factory-configured either as Power Good (ST1S09PUR) or Inhibit (ST1S09IPUR). The ST1S09PUR part has PG functionality only; connecting it to an external pull-up enables open-drain status reporting, but it cannot accept inhibit signals.

How does the dual supply (VIN_A and VIN_SW) improve regulation accuracy?

VIN_A powers the error amplifier, PWM comparator, and reference circuitry, isolating sensitive analog blocks from switching noise on VIN_SW. This separation reduces PSRR degradation and maintains <0.16 % line regulation even under high di/dt load steps, as confirmed in Table 6 electrical characteristics.

Is the exposed thermal pad electrically connected internally?

Yes - the exposed pad is internally connected to GND and must be soldered to a PCB ground plane. Per mechanical data (Figure 23), it provides 10 °C/W junction-to-case thermal resistance and is essential for achieving rated 2 A output current without derating above 85 °C ambient.