STMicroelectronics A7986A

Overview

A7986A from STMicroelectronics is a 3 A automotive-grade step-down switching regulator with integrated 3.7 A P-channel MOSFET, operating from 4.5 V to 38 V input and delivering adjustable output down to 0.6 V. It features 250 kHz base switching frequency (programmable up to 1 MHz), internal soft-start, 100% duty-cycle low-dropout operation, and AEC-Q100 qualification for under-hood use in LED driver and body control modules.

For engineers reviewing the A7986A datasheet, A7986A pinout, A7986A application, or A7986A equivalent, this device is selected for high-input-voltage DC/DC conversion where thermal robustness (R_th(JA) = 40 °C/W), synchronization capability, voltage feed-forward stability, and zero-load quiescent current (20–30 µA) are critical design requirements.

Technical Context

The A7986A 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) to maintain constant loop gain across line and frequency variations. Its error amplifier delivers 100 dB DC gain, 4.5 MHz GBWP, and rail-to-rail output swing (0–3.3 V) for stable Type II/III compensation.

Overcurrent protection uses pulse-by-pulse current limiting with 200 ns blanking time and adaptive pulse-skipping (up to 7 skipped cycles) to clamp output current at 3.7 A (min) while reducing effective switching frequency to 1/8th nominal during sustained overload-enabling controlled short-circuit current regulation without thermal runaway.

Key Specifications

Pinout & Package

Package: HSOP8 with exposed thermal pad (pin 0), optimized for low R_th(JA) (40 °C/W) and automotive board space constraints.

Key Features

Applications

Equivalent & Alternatives

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

Compared with LM5164QPWPRQ1 and MPQ4433-AEC1, the A7986A uniquely combines AEC-Q100 qualification, 38 V input tolerance, synchronization support, and voltage/frequency feed-forward-making it optimal for thermally constrained, multi-rail automotive systems requiring coordinated switching and robust line regulation.

Availability

A7986A is available at Aetrix Electronics and suitable for automotive LED driving, body control modules, start-stop auxiliary rails, and infotainment display power supplies requiring stable component supply across extended temperature and lifecycle demands.

Supply support for A7986A 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 automotive, industrial, and power management solutions with broad manufacturing and quality certification infrastructure.

The A7986A belongs to ST's automotive-qualified power management IC portfolio, designed specifically for high-reliability DC/DC conversion in engine bay, lighting, and chassis control applications where AEC-Q100 compliance and thermal resilience are mandatory.

FAQ

What is the minimum output voltage achievable with the A7986A?

The A7986A has an internal feedback reference of 0.6 V ±2%, and its output voltage is set using an external resistor divider from V_OUT to the FB pin. With proper divider design and layout, the device regulates stably down to exactly 0.6 V - no lower output is supported, as the reference is fixed and not programmable below this value.

Can the A7986A operate with input voltage below 4.5 V?

No. The A7986A incorporates an undervoltage lockout (UVLO) with a turn-on threshold of 4.5 V (typical) and 0.4 V hysteresis. Below 4.5 V, the device remains disabled and draws only leakage current. Operation below this threshold is not functional or characterized, and attempting to force operation may result in erratic behavior or failure to start.

How does the SYNCH pin behave when left unconnected?

When the SYNCH pin is left floating, the A7986A outputs a square wave at its internal switching frequency (250 kHz default) with a 180° phase shift relative to the internal power switch turn-on edge. This built-in inverted clock enables natural interleaving when two devices are synchronized by tying their SYNCH pins together - one automatically becomes master, the other slave, with half-period phase offset.

Is external compensation required for stable operation?

Yes. The A7986A requires an external Type II or Type III compensation network connected between COMP and FB pins. The choice depends on output capacitor ESR: Type II suffices for high-ESR electrolytics; Type III is mandatory for low-ESR ceramics to ensure ≥45° phase margin. ST provides detailed design equations and example values in Section 6.4 of the datasheet.