STMicroelectronics ST1S03PUR

Overview

ST1S03PUR from STMicroelectronics is a 1.5 A, 1.5 MHz adjustable step-down DC-DC switching regulator in a DFN6D (3 × 3 mm) package with exposed thermal pad. It implements current-mode PWM control, delivers ±2% DC output voltage tolerance, features internal soft-start (50–100 µs power-on delay), and supports input voltage range of 3 V to 16 V. Designed for low-voltage digital core power in HDD systems, it replaces high-dissipation linear regulators.

For engineers reviewing the ST1S03PUR datasheet, ST1S03PUR pinout, ST1S03PUR application, or ST1S03PUR equivalent, key selection criteria include its 1.5 A continuous output capability, 1.5 MHz fixed-frequency operation enabling compact external components, internal compensation eliminating loop compensation parts, thermal shutdown at 130–150 °C, and dual-supply architecture (VIN_SW/VIN_A) for optimized analog and switch domain biasing.

Technical Context

The ST1S03PUR integrates a 1.5 A internal N-channel MOSFET switch with 350 mV max R_DS(on) at 750 mA, operating in constant-frequency current-mode PWM topology. Its dual-input architecture separates analog supply (VIN_A) from switch supply (VIN_SW), reducing noise coupling and improving regulation stability across load transients.

Internal soft-start generates a controlled voltage ramp on the feedback node to limit inrush current, while cycle-by-cycle current limiting and thermal shutdown (130–150 °C trip, 15 °C hysteresis) provide robust fault protection. Output voltage is externally adjustable via resistor divider using a precise 800 mV (±2%) feedback reference.

Key Specifications

Pinout & Package

ST1S03PUR is housed in a thermally enhanced DFN6D package (3 mm × 3 mm, 0.8 mm height) with an exposed pad (EP) that must be soldered to a PCB ground plane for optimal thermal performance and electrical stability.

Key Features

Applications

Equivalent & Alternatives

The following parts are listed as comparable options for similar adjustable step-down regulator applications.

Compared with TPS54302DDCR and ADP2303ARDZ-REEL7, ST1S03PUR uniquely combines dual-supply domains, internal compensation, and 1.5 MHz operation in a 3×3 mm DFN-making it optimal for noise-sensitive, space-constrained digital core supplies requiring minimal BOM count and predictable thermal behavior.

Availability

ST1S03PUR is available at Aetrix Electronics and suitable for HDD digital core power, industrial PLC I/O modules, automotive infotainment SoC supplies, and telecom line card biasing requiring stable component supply, long-term lifecycle support, and RoHS-compliant packaging.

Supply support for ST1S03PUR 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 microcontrollers, power management ICs, sensors, and analog products for industrial, automotive, and consumer markets.

The ST1S03PUR belongs to ST's high-efficiency DC-DC converter product line, engineered specifically to replace linear regulators in high-current, low-voltage digital core applications where thermal management and PCB area are critical constraints.

FAQ

What is the minimum recommended output capacitor value for stable operation?

The ST1S03PUR is characterized with a 22 µF X5R/X7R ceramic output capacitor and remains stable down to 10 µF when using low-ESR MLCCs. Lower values may cause instability or increased ripple; ST recommends ≥15 µF with ≤10 mΩ ESR for full 1.5 A load range and thermal safety margin.

Can VIN_A and VIN_SW be tied together in a single-supply design?

Yes - VIN_A and VIN_SW may be connected to the same 3–16 V source if noise isolation is not required. However, doing so forfeits the PSRR and transient immunity benefits of separate supplies; ST specifies 100 nF decoupling per input when combined, and recommends separate 1 µF + 100 nF filtering if shared.

Does the ST1S03PUR support forced PWM mode at light loads?

No - the ST1S03PUR automatically enters pulse-skipping mode below ~100 mA to maintain efficiency; it does not offer a forced PWM pin or mode selection. For constant-frequency operation across all loads, consider ST's ST1S12 or ST1S14 series, which include MODE pin control.

How should the exposed pad (EP) be connected for optimal thermal performance?

The EP must be soldered to a dedicated GND copper pour covering ≥25 mm², with ≥4 thermal vias (0.3 mm diameter, spaced ≤1 mm apart) connecting to inner-layer or backside ground planes. ST's datasheet specifies R_thJA = 55 °C/W only when EP is fully connected; omitting vias increases junction temperature by >30 °C at full load.