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

STMicroelectronics A7985ATR

Name: A7985ATR
Brand: STMicroelectronics
SKU: A7985ATR
Price: 2.40 USD
Availability: InStock
Rating: 5 (2 reviews)

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Part No.:: A7985ATR

Manufacturer:: STMicroelectronics

Category:: Voltage Regulators - DC DC Switching Regulators

Package:: 8-SOIC (0.154", 3.90mm Width) Exposed Pad

Datasheet:: A7985ATR.pdf

Description:: IC REG BUCK ADJ 2A 8HSOP

Quantity:: RFQ Add To RFQ list

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Inventory:19,656

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Product details

Overview

A7985ATR from STMicroelectronics is a 2 A automotive-grade step-down switching regulator with integrated P-channel MOSFET, operating from 4.5 V to 38 V input and delivering adjustable output down to 0.6 V. It features AEC-Q100 qualification, 250 kHz–1 MHz programmable switching frequency, internal soft-start, 100% duty-cycle low-dropout operation, and voltage feed-forward for line transient immunity - deployed in automotive LED driving and body control modules.

For engineers reviewing the A7985ATR datasheet, A7985ATR pinout, A7985ATR application, or A7985ATR equivalent, this page delivers verified technical context on its voltage-mode control architecture, HSOP8 thermal performance (R_th(JA) = 40 °C/W), peak current limit (2.5 A min), feedback reference accuracy (±2%), and synchronization capability for multi-phase buck designs.

Technical Context

The A7985ATR implements voltage-mode PWM control with a fixed-frequency sawtooth oscillator whose slope is dynamically adjusted via voltage feed-forward (input-dependent ramp scaling) and frequency feed-forward (FSW-resistor–adjusted ramp scaling), maintaining constant PWM gain across input and frequency variations. Its error amplifier features 100 dB open-loop gain, rail-to-rail COMP output sourcing/sinking capability (19 mA/30 mA), and direct access to FB and COMP pins for Type II or Type III compensation.

Functional blocks include an embedded high-side P-MOSFET driver, peak-current-limit sensing (2.5 A min), hysteretic thermal shutdown at 150 °C (30 °C hysteresis), UVLO with 4.5 V turn-on threshold and 0.1–0.4 V hysteresis, and SYNCH pin supporting master/slave phase interleaving or external clock synchronization with zero-phase-shift locking.

Key Specifications

Parameter	Value and Actual Design Meaning
Input voltage range	4.5 V to 38 V - supports full automotive battery range including cold-crank (4.5 V) and load-dump (38 V) transients.
Output current	Up to 2 A DC - limited by thermal design and external component selection; internal MOSFET rated for 2.5 A peak current.
Feedback reference	0.6 V ±2% - enables precise output regulation; sets minimum V_OUT; used with resistor divider for higher outputs.
Switching frequency	250 kHz (default) to 1 MHz - adjustable via FSW pin resistor; higher frequencies reduce inductor size but increase switching loss.
MOSFET R_DS(on)	200–400 mΩ (typ/max) - defines conduction loss and thermal rise; impacts efficiency at high load currents.
Soft-start duration	7.3–9.8 ms (at 250 kHz) - prevents inrush current; scales inversely with switching frequency (SSTIME = 2048 / F_SW).
Thermal resistance	R_th(JA) = 40 °C/W - measured on demo board; requires HSOP8 exposed pad soldering for specified junction-to-ambient performance.

Pinout & Package

Package: HSOP8 with exposed thermal pad (mechanical outline per DocID023128 Rev 8, Table 10). Exposed pad must be soldered to PCB ground plane for thermal and electrical integrity.

Pin/Terminal	Circuit Role	Design Meaning
1 OUT	Regulated output node	Power switch source terminal; connects directly to LC filter output; carries full load current and high di/dt.
2 SYNCH	Synchronization I/O	Configurable as master (output) or slave (input); enables phase-interleaved operation or external clock lock with zero phase shift.
3 EN	Enable control input	Active-high logic interface (ON > 1.2 V, OFF < 0.3 V); supports system-level power sequencing and standby mode.
4 COMP	Error amplifier output	Direct access to EA output for external compensation network (Type II/III); sinks 30 mA, sources 19 mA.
5 FB	Feedback input	High-impedance node referenced to 0.6 V internal bandgap; senses output via resistor divider for regulation.
6 FSW	Frequency programming	Connects to ground via resistor to set switching frequency (250 kHz–1 MHz); floating = default 250 kHz.
7 GND	Power and signal ground	Common return path for power stage, control circuitry, and compensation network; tied to exposed pad.
8 VCC	Unregulated input supply	Primary power input (4.5–38 V); powers internal LDO, gate driver, and bias circuitry; requires local decoupling.

Key Features

Feature	Design Value
AEC-Q100 qualified	Qualified for automotive applications (Grade 1: –40 °C to +125 °C ambient), including PPAP documentation support.
Voltage feed-forward	Adjusts sawtooth slope proportional to V_IN, stabilizing PWM gain during line transients without loop compensation changes.
Zero-load operation	Maintains regulation with no output load - critical for always-on automotive modules (e.g., CAN wake-up circuits).
100% duty cycle capability	Enables dropout operation down to V_OUT ≈ V_IN − I_LOAD × R_DS(on); supports wide-input-range systems during low-V_IN conditions.
Internal soft-start	64-step staircase ramp on EA reference (0 → 0.6 V); eliminates output overshoot and inrush stress on input capacitors.

Applications

Automotive LED Headlamp Driver

Body Control Module (BCM) Power Supply

Use Scenario: Regulating 12 V battery to 5.5 V/2 A for LED driver ICs and microcontrollers in adaptive front-lighting systems.

IC Role / Device Role / Timing Role: Primary buck converter supplying stable mid-rail power; handles cold-crank dips and load-dump surges.

Use Value: Voltage feed-forward ensures consistent LED brightness during alternator voltage fluctuations; AEC-Q100 compliance guarantees reliability over 15-year vehicle lifetime.

Use Scenario: Generating 3.3 V/1.5 A from 12 V battery for CAN transceivers, door module MCUs, and sensor interfaces.

IC Role / Device Role / Timing Role: System power regulator with enable control synchronized to vehicle ignition state.

Use Value: Internal soft-start prevents brown-out during BCM power-up; 100% duty cycle maintains operation during cranking (down to 4.5 V).

Infotainment System Core Rail

ADAS Camera Power Subsystem

Use Scenario: Delivering 1.8 V/2 A to application processors and DDR memory in head-unit systems.

IC Role / Device Role / Timing Role: High-efficiency intermediate buck stage feeding downstream LDOs or POL converters.

Use Value: Programmable 1 MHz switching enables compact 2.2 µH inductors; HSOP8 thermal performance supports continuous 2 A under 85 °C ambient.

Use Scenario: Providing isolated 5 V/1 A and 3.3 V/0.5 A rails for image sensors and ISP SoCs in surround-view cameras.

IC Role / Device Role / Timing Role: Primary regulator with SYNC pin enabling interleaved dual-buck configuration to halve input ripple.

Use Value: Phase-shifted synchronization reduces RMS input capacitor current by ~30%, extending MLCC life in high-temp camera housings.

Equivalent & Alternatives

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

Alternative Part	Technical Difference	Application Difference	Selection Advice
LMQ61460QRJRQ1	N-channel MOSFET controller (external high-side FET); 3.3–36 V input; 6 A max; no internal P-FET.	Requires external high-side MOSFET and bootstrap circuit; better suited for >3 A loads and higher efficiency at light load.	Select when higher output current (>2.5 A) or lower quiescent current (<20 µA) is required; not drop-in due to topology and pinout differences.
TPS54560BQPWPRQ1	Current-mode control; 3.5–60 V input; 5 A max; integrated N-FET; no voltage feed-forward.	Lacks voltage feed-forward, requiring more complex loop compensation for line transient immunity; larger package (HTSSOP-20).	Prefer for wider input range (up to 60 V) or higher current; avoid where strict line-transient response (e.g., LED dimming) is critical.

Compared with LM61460QRJRQ1 and TPS54560BQPWPRQ1, the A7985ATR offers integrated P-FET simplicity and voltage feed-forward for superior line regulation in 2 A automotive rails, while trading off maximum current and ultra-low IQ - making it optimal for cost-sensitive, thermally constrained 12 V subsystems.

Availability

A7985ATR is available at Aetrix Electronics and suitable for automotive LED driving, body control modules, infotainment core supplies, and ADAS camera power subsystems requiring stable component supply across extended temperature and long-lifecycle programs.

Supply support for A7985ATR 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 automotive ICs with vertical fabrication capabilities.

The A7985ATR belongs to ST's automotive-qualified power management portfolio, engineered specifically for robust, high-reliability DC-DC conversion in harsh vehicle environments - emphasizing AEC-Q100 compliance, thermal resilience, and transient immunity.

FAQ

What is the minimum input voltage required for A7985ATR startup?

The A7985ATR requires a minimum V_CC of 4.5 V to initiate operation, as defined by its UVLO turn-on threshold. Below this, the device remains disabled regardless of EN state. This ensures reliable startup during automotive cold-crank events while preventing erratic behavior at marginal voltages.

Can A7985ATR operate with ceramic output capacitors only?

Yes - the A7985ATR supports ceramic output capacitors and recommends Type III compensation for low-ESR ceramics (e.g., X7R/X5R MLCCs). Its error amplifier and feed-forward architecture maintain stability with typical 10–47 µF ceramic banks, eliminating need for bulk electrolytic capacitance in space-constrained designs.

How does the SYNCH pin behave when left floating?

When the SYNCH pin is left floating, it outputs a square wave synchronized to the internal oscillator with 180° phase shift relative to the power switch turn-on. This enables natural phase interleaving when two A7985ATRs are connected via SYNCH pins - the higher-frequency unit becomes master, the other slave, achieving half-period offset without external timing components.

Is external compensation mandatory for A7985ATR?

Yes - external compensation is mandatory. The COMP and FB pins provide direct access to the error amplifier's output and inverting input, requiring a Type II or Type III network (per output capacitor ESR) to ensure loop stability. No internal compensation is provided; omission results in oscillation or poor transient response.

A7985ATR Specifications

Product attributes: Attribute value

Manufacturer:: STMicroelectronics

Series:: -

Package/Case:: 8-SOIC (0.154", 3.90mm Width) 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):: 4.5V

Voltage - Input (Max):: 38V

Voltage - Output (Min/Fixed):: 0.6V

Voltage - Output (Max):: 38V

Current - Output:: 2A

Frequency - Switching:: 250kHz

Synchronous Rectifier:: No

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

Grade:: Automotive

Qualification:: AEC-Q100

Mounting Type:: Surface Mount

Supplier Device Package:: 8-HSOP-EP

A7985ATR FAQ

1.How can I place an order for A7985ATR through Aetrix?

Please submit a Request for Quotation (RFQ) for A7985ATR 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 A7985ATR reliable?

The price and inventory of A7985ATR are updated periodically and may fluctuate due to market conditions. Stock and pricing data are typically refreshed every 24 hours. Quotation validity for A7985ATR is usually 5 days.

3.What payment methods are accepted for A7985ATR?

We accept Wire Transfer, PayPal, Credit Card, Western Union, MoneyGram, and Escrow for A7985ATR transactions.

Note: Certain payment methods may incur a processing fee.

4.How is shipping managed for A7985ATR?

A7985ATR orders can be shipped via leading logistics carriers, including DHL, UPS, FedEx, TNT, or Registered Mail.

Once your A7985ATR 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 A7985ATR?

For technical support, including A7985ATR datasheets, pinout diagrams, or application guidance, please contact our engineering support team. They can provide detailed documentation and assistance for your A7985ATR requirements.

6.How does Aetrix verify that A7985ATR is sourced from the original manufacturer or authorized distributors?

All A7985ATR 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 A7985ATR meets industry standards.

7.What is the process for return or replacement of A7985ATR?

All A7985ATR units undergo pre-shipment inspection (PSI). If there is an issue with A7985ATR, 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 A7985ATR part is unused and in its original packaging.

Return procedure for A7985ATR:

1.Submit a request within 90 days.

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

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