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Home > Products > Integrated Circuits (ICs) > Power Management (PMIC) > Voltage Regulators - DC DC Switching Regulators

STMicroelectronics AST1S31HF

Name: AST1S31HF
Brand: STMicroelectronics
SKU: AST1S31HF
Price: 2.40 USD
Availability: InStock
Rating: 5 (2 reviews)

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Part No.:: AST1S31HF

Manufacturer:: STMicroelectronics

Category:: Voltage Regulators - DC DC Switching Regulators

Package:: 8-VDFN Exposed Pad

Datasheet:: AST1S31HF.pdf

Description:: IC REG BUCK ADJ 3A 8VFDFPN

Quantity:: RFQ Add To RFQ list

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Inventory:4,837

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Product details

Overview

AST1S31HF from STMicroelectronics is a synchronous step-down DC-DC regulator for automotive systems, delivering up to 3 A output current with 2.3 MHz fixed-frequency PWM control, 0.8 V to VIN adjustable output, and integrated 70 mΩ high-side / 55 mΩ low-side MOSFETs in a VFDFPN 3 × 3 mm package.

For engineers reviewing the AST1S31HF datasheet, AST1S31HF pinout, AST1S31HF application, or AST1S31HF equivalent, this device supports AEC-Q100 Grade 1 qualification, cycle-by-cycle current limiting, Power Good (PG) monitoring, internal soft-start, and all-ceramic capacitor compatibility in compact body electronics power rails.

Technical Context

The AST1S31HF employs peak current mode control with internal compensation, enabling stable regulation across 2.8–4 V input while supporting output voltages as low as 0.8 V. Its architecture integrates slope compensation to prevent sub-harmonic oscillation above 50% duty cycle and embeds transconductance error amplifier (gm = 236 µA/V, DC gain = 87 dB) with internal RC/CC network (80 kΩ / 55 pF).

Overcurrent protection operates in two stages: cycle-by-cycle limiting at ≥3.6 A typical, followed by current foldback and frequency reduction when FB < 0.2 V; thermal shutdown activates at 150 °C with 20 °C hysteresis. Light-load efficiency is enhanced via frequency reduction when error amplifier output falls below threshold.

Key Specifications

Parameter	Value and Actual Design Meaning
Input Voltage Range	2.8 V to 4 V - supports direct connection to automotive battery rail with transient tolerance up to 5 V absolute max.
Output Current	3 A DC - delivers full rated load without external heatsink under typical ambient conditions (TA < 60 °C).
Switching Frequency	2.3 MHz (typ.) - enables use of small external inductors (< 1 µH) and ceramic capacitors for space-constrained modules.
Feedback Reference	0.8 V (±1.25%) - sets output voltage via resistor divider; enables precise low-VOUT regulation down to 0.8 V.
Power MOSFET RDS(on)	70 mΩ HS / 55 mΩ LS - minimizes conduction loss at 3 A, achieving >90% efficiency at 3.3 V_IN/1.2 V_OUT.
Soft-Start Duration	400 µs - limits inrush current during startup, preventing input rail droop and ensuring monotonic V_OUT ramp.
Power Good Threshold	92–96% of regulated V_OUT - provides accurate output monitoring with 170 µs delay for reliable system sequencing.

Pinout & Package

AST1S31HF is housed in a thermally enhanced VFDFPN 3 mm × 3 mm × 1.0 mm, 8-lead package with exposed ePAD (Pin 9) for improved thermal dissipation and grounding.

Pin/Terminal	Circuit Role	Design Meaning
VINA	Unregulated input supply	Bypassed separately from VINSW to reduce noise coupling into switching node.
EN	Enable control input	Logic-compatible (ON > 1.5 V, OFF < 0.5 V); internal pull-down ensures safe default-off state.
FB	Feedback sensing node	Connects to resistor divider; regulates output to 0.8 V reference; sensitive to PCB layout parasitics.
AGND	Analog ground reference	Separate from PGND to minimize noise injection into feedback and error amplifier circuits.
PG	Open-drain Power Good	Signals valid output after 170 µs delay; requires external pull-up for microcontroller reset or sequencing logic.
VINSW	High-side switch input	Connected directly to input capacitor; carries high di/dt switching current - critical for layout.
SW	Switching node	Drives external inductor; high dv/dt node requiring minimized trace area and guard ring.
PGND	Power ground return	Low-impedance path for high-current switch return; tied to ePAD for thermal and EMI performance.

Key Features

Feature	Design Value
AEC-Q100 qualified	Grade 1 (−40 °C to +125 °C junction), validated for automotive body electronics and infotainment power rails.
Integrated power switches	70 mΩ P-channel HS + 55 mΩ N-channel LS MOSFETs eliminate external FETs and gate drivers.
All-ceramic capacitor support	Stable operation with MLCC input/output capacitors only - no electrolytic or tantalum required.
Internal soft-start & enable	400 µs monotonic startup and logic-level EN pin simplify system power sequencing and reduce BOM count.
Current foldback protection	Reduces switching frequency under short-circuit to limit average output current to ~1.5 A, preventing thermal runaway.

Applications

Automotive Body Control Module (BCM)

ADAS Camera Power Supply

Use Scenario: Regulating 12 V battery-derived input to 3.3 V or 5 V for microcontrollers, LIN transceivers, and LED drivers in door modules and lighting controllers.

IC Role / Device Role / Timing Role: Primary buck converter supplying core logic voltage with Power Good signaling for safe MCU boot sequence.

Use Value: AEC-Q100 qualification and 2.3 MHz operation allow compact layout in tight BCM enclosures while meeting automotive EMC and thermal requirements.

Use Scenario: Providing clean, low-noise 1.2 V supply to image sensor SoCs in rear-view or surround-view cameras.

IC Role / Device Role / Timing Role: High-efficiency synchronous buck regulator with precise 0.8 V reference enabling accurate low-VOUT regulation.

Use Value: Integrated MOSFETs and all-ceramic support eliminate ESR-related ripple, reducing sensor noise and improving image SNR.

Automotive Infotainment Display Backlight

Telematics Control Unit (TCU) Core Rail

Use Scenario: Generating 5 V from 12 V battery for LED driver ICs powering TFT-LCD backlight arrays.

IC Role / Device Role / Timing Role: High-current (3 A) buck stage feeding downstream boost or linear LED drivers.

Use Value: 3 A capability and thermal shutdown with hysteresis ensure sustained operation during display brightness transitions without derating.

Use Scenario: Delivering stable 1.1 V or 1.3 V core voltage to cellular modem SoCs in vehicle telematics units.

IC Role / Device Role / Timing Role: Primary point-of-load regulator with fast transient response and PG signaling for modem power sequencing.

Use Value: Internal compensation and 230 kHz loop bandwidth (per Bode plot) enable robust regulation under dynamic data transmission loads.

Equivalent & Alternatives

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

Alternative Part	Technical Difference	Application Difference	Selection Advice
TPS62130ARGTR	3 A, 3–17 V input, 2.5 MHz, 0.8 V ref, but not AEC-Q100 qualified; uses external compensation.	Suitable for industrial or consumer portable devices, not automotive-grade systems.	Select only if AEC-Q100 compliance is unnecessary and wider VIN range is required.
MPQ4420AGL-A	2 A, 3.3–36 V input, 2.2 MHz, 0.8 V ref, AEC-Q100 Grade 1, but lower current rating and higher R_DS(on) (110/75 mΩ).	Acceptable for lower-power automotive modules where 2 A suffices and cost is prioritized.	Choose when footprint compatibility is acceptable and 3 A headroom is not required.

Compared with TPS62130ARGTR and MPQ4420AGL-A, AST1S31HF uniquely combines AEC-Q100 Grade 1, 3 A output, 2.3 MHz switching, and integrated 70/55 mΩ MOSFETs in a 3 × 3 mm VFDFPN - making it optimal for space- and reliability-critical automotive body electronics.

Availability

AST1S31HF is available at Aetrix Electronics and suitable for automotive body control modules, ADAS camera power supplies, and telematics control unit core rails requiring stable component supply, long-term lifecycle assurance, and AEC-Q100-compliant sourcing.

Supply support for AST1S31HF 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, power, microcontroller, and automotive-grade ICs for industrial, automotive, and consumer markets.

The AST1S31HF belongs to ST's automotive-qualified power management portfolio, engineered specifically for compact, high-reliability DC-DC conversion in car body electronics and infotainment subsystems operating from low-voltage battery rails.

FAQ

What is the minimum recommended output voltage for AST1S31HF?

The AST1S31HF supports output voltages as low as 0.8 V, set by its internal feedback reference. This value is guaranteed across temperature (−40 °C to +125 °C) and load (0–3 A), with ±1.25% tolerance. Lower outputs are not supported due to internal reference architecture and minimum off-time constraints (66 ns).

Does AST1S31HF require external compensation components?

No. The AST1S31HF features fully internal loop compensation using an integrated 80 kΩ resistor and 55 pF capacitor network. This eliminates external compensation components, reduces BOM count, and ensures stability across all operating conditions without design iteration.

How does the Power Good (PG) pin behave during startup and fault conditions?

The PG pin is open-drain and asserts high-Z when V_OUT reaches ≥92% of target (e.g., 1.104 V for 1.2 V output) after a fixed 170 µs delay. If V_OUT drops below 92%, PG pulls low immediately. During UVLO or thermal shutdown, PG goes low without delay, enabling real-time fault detection.

Can AST1S31HF operate with input voltage below 2.8 V?

No. The absolute minimum operating input voltage is 2.8 V per datasheet specifications. Below this, the device may fail to regulate or enter undervoltage lockout (UVLO). The turn-on threshold is 2.3–2.45 V, but stable regulation is only guaranteed from 2.8 V to 4 V.

AST1S31HF Specifications

Product attributes: Attribute value

Manufacturer:: STMicroelectronics

Series:: -

Package/Case:: 8-VDFN Exposed Pad

Packaging:: Tape & Reel (TR)

Product Status:: Active

Function:: Step-Down

Output Configuration:: Positive

Topology:: Buck

Output Type:: Adjustable

Number of Outputs:: 1

Voltage - Input (Min):: 2.8V

Voltage - Input (Max):: 4V

Voltage - Output (Min/Fixed):: 0.8V

Voltage - Output (Max):: 4V

Current - Output:: 3A

Frequency - Switching:: 2.3MHz

Synchronous Rectifier:: Yes

Operating Temperature:: -40°C ~ 150°C (TJ)

Grade:: Automotive

Qualification:: AEC-Q100

Mounting Type:: Surface Mount

Supplier Device Package:: 8-VFDFPN (3x3)

AST1S31HF FAQ

1.How can I place an order for AST1S31HF through Aetrix?

Please submit a Request for Quotation (RFQ) for AST1S31HF on Aetrix. Our sales agent will provide a competitive quotation and guide you through the order confirmation once you accept the terms.

2.Are the price and stock information for AST1S31HF reliable?

The price and inventory of AST1S31HF are updated periodically and may fluctuate due to market conditions. Stock and pricing data are typically refreshed every 24 hours. Quotation validity for AST1S31HF is usually 5 days.

3.What payment methods are accepted for AST1S31HF?

We accept Wire Transfer, PayPal, Credit Card, Western Union, MoneyGram, and Escrow for AST1S31HF transactions.

Note: Certain payment methods may incur a processing fee.

4.How is shipping managed for AST1S31HF?

AST1S31HF orders can be shipped via leading logistics carriers, including DHL, UPS, FedEx, TNT, or Registered Mail.

Once your AST1S31HF order is processed, you will receive an email with the shipment details and tracking number.

Note: Tracking information may take up to 24 hours to appear. Express delivery typically takes 3–5 business days.

5.How can I obtain technical support or documentation for AST1S31HF?

For technical support, including AST1S31HF datasheets, pinout diagrams, or application guidance, please contact our engineering support team. They can provide detailed documentation and assistance for your AST1S31HF requirements.

6.How does Aetrix verify that AST1S31HF is sourced from the original manufacturer or authorized distributors?

All AST1S31HF products on Aetrix are procured from qualified distributors and authorized channels. Our dedicated quality assurance team conducts strict verification, including traceability checks and, if necessary, third-party testing. This ensures that AST1S31HF meets industry standards.

7.What is the process for return or replacement of AST1S31HF?

All AST1S31HF units undergo pre-shipment inspection (PSI). If there is an issue with AST1S31HF, returns or replacements are accepted under the following conditions:

1.Quantity discrepancies, incorrect items, or visible external defects (such as breakage or corrosion), acknowledged by Aetrix.

2.The issue is reported within 90 days of delivery.

3.The AST1S31HF part is unused and in its original packaging.

Return procedure for AST1S31HF:

1.Submit a request within 90 days.

2.Obtain a Return Material Authorization (RMA) from Aetrix.

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