STMicroelectronics ST1S40IPHR

Overview

ST1S40IPHR from STMicroelectronics is a 3 A synchronous step-down DC-DC regulator with fixed 850 kHz switching frequency, 4.0–18 V input range, and adjustable output down to 0.8 V. It integrates 95 mΩ high-side and 69 mΩ low-side Power MOSFETs, supports all-ceramic capacitor designs, and delivers high efficiency in µP/ASIC/FPGA core supply applications.

For engineers reviewing the ST1S40IPHR datasheet, ST1S40IPHR pinout, ST1S40IPHR application, or ST1S40IPHR equivalent, key selection criteria include its internal soft-start duration (1 ms), cycle-by-cycle current limiting, thermal shutdown at 150 °C, and compatibility with HSOP-8, VFQFPN4x4-8L, and SO8 packages.

Technical Context

The ST1S40IPHR employs peak current mode control with an internally compensated transconductance error amplifier (Gm = 251 µA/V, Ro = 240 MΩ) and embedded slope compensation to prevent sub-harmonic oscillation above 50% duty cycle. Its oscillator provides a stable 850 kHz clock with ±15% tolerance and integrates UVLO monitoring for VINA and VINSW rails.

Functional protection includes dual-threshold overcurrent detection (OCP1 ≈ 4–6 A, OCP2 ≈ OCP1 + 1 A), current fold-back under sustained overload (limiting to ~2 A), and hysteretic thermal shutdown (trip at 150 °C, restart at ~130 °C). The enable function operates with TTL-compatible thresholds (ON ≥ 1.2 V, OFF ≤ 0.4 V) and draws ≤15 µA in standby.

Key Specifications

Pinout & Package

ST1S40IPHR is packaged in HSOP-8 (exposed pad), with pin 1 marked by a dot. The exposed thermal pad (ePad) must be soldered to a dedicated ground copper area for optimal thermal performance (R_thJA = 40 °C/W on demo board).

Key Features

Applications

Equivalent & Alternatives

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

Compared with TPS54332DR and MP2332HG-LL-Z, ST1S40IPHR offers superior integration (internal MOSFETs, compensation, soft-start, and dual OCP thresholds), enabling smaller PCB area, faster design cycle, and robust protection without additional components.

Availability

ST1S40IPHR is available at Aetrix Electronics and suitable for µP/ASIC/DSP/FPGA core supplies, point-of-load conversion in STBs and TVs, optical storage systems, and hard disk drive power management requiring stable component supply and long-term industrial availability.

Supply support for ST1S40IPHR 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, microcontrollers, and analog ICs for industrial, automotive, and consumer markets.

The ST1S40 belongs to ST's high-efficiency synchronous buck regulator product line, designed specifically for space-constrained, high-current point-of-load applications in digital consumer electronics and computing peripherals.

FAQ

What is the minimum output voltage achievable with ST1S40IPHR?

The ST1S40IPHR regulates output down to 0.8 V, set by its internal feedback reference voltage. This value is guaranteed across temperature (–40 °C to +125 °C) and line/load conditions, with typical tolerance of ±2% (0.784–0.816 V). Lower outputs require external circuitry and are not supported.

Can ST1S40IPHR operate with only ceramic capacitors on input and output?

Yes - ST1S40IPHR is explicitly designed for all-ceramic capacitor operation. Its internal compensation and peak current mode architecture remain stable with low-ESR MLCCs. Recommended input: ≥10 µF 25 V ceramic; output: ≥22 µF 6.3 V MLCC with ESR <5 mΩ.

How does the current fold-back protection behave during output short-circuit?

Under sustained short-circuit, ST1S40IPHR reduces switching frequency to 212.5 kHz (¼ of nominal) and lowers current limit to ~2 A. This fold-back reduces power dissipation and prevents thermal runaway. The feature is disabled during soft-start to ensure reliable initial charging of large output capacitors.

Is the NC pin on ST1S40IPHR required to be grounded?

No - the NC pin is internally unconnected and serves no electrical function. It may be left floating, grounded, or tied to GND for mechanical reinforcement. STMicroelectronics' datasheet states it "can be connected to ground" but confirms no impact on operation or reliability when left unconnected.