STMicroelectronics A7987TR

Overview

A7987TR from STMicroelectronics is a 61 V, 3 A asynchronous step-down switching regulator with adjustable current limit, voltage-mode control, and AEC-Q100 qualification. It delivers regulated DC output from 0.8 V to VIN across 4.5–61 V input, supports synchronization up to 1.5 MHz, and integrates VBIAS-assisted light-load efficiency enhancement for automotive 24 V battery systems.

For engineers reviewing the A7987TR datasheet, A7987TR pinout, A7987TR application, or A7987TR equivalent, key selection criteria include its 250 kHz–1.5 MHz programmable fSW, 0.8 V ±1% FB reference, PGOOD open-collector monitoring, digital frequency fold-back under short-circuit, and thermal shutdown at 170 °C with 15 °C hysteresis.

Technical Context

The A7987TR implements a voltage-mode PWM control loop with internal 0.8 V reference, sawtooth ramp generator, and feed-forward compensation that maintains constant PWM gain across input voltage and switching frequency variations. Its oscillator supports master/slave synchronization via the SYNCH pin with 180° phase shift, enabling noise-sensitive multi-phase operation in infotainment systems.

Overcurrent protection uses pulse-by-pulse sensing with 120 ns blanking time, programmable ILIM (0.69–4.4 A), and digital frequency fold-back-reducing fSW to 1/8 nominal during sustained overload. Thermal shutdown activates at 170 °C with auto-recovery, and VBIAS switchover (2.84–4.90 V threshold) improves light-load efficiency by powering analog circuitry from the regulated output.

Key Specifications

Pinout & Package

Package: HTSSOP-16 (exposed pad), RoHS-compliant, thermally enhanced for automotive-grade power dissipation (R_thJA = 40 °C/W).

Key Features

Applications

Equivalent & Alternatives

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

Compared with LM61480QPWPRQ1 and MPQ4420AGL-AEC1, the A7987TR uniquely balances 3 A output, AEC-Q100 Grade 1 qualification, VBIAS-enabled light-load efficiency, and PGOOD-based sequencing-making it optimal for mid-power automotive ECUs needing both robustness and flexibility.

Availability

A7987TR is available at Aetrix Electronics and suitable for automotive ADAS camera modules, infotainment head units, body control modules, and electric power steering ECUs requiring stable component supply across extended temperature and lifecycle demands.

Supply support for A7987TR 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 ICs, sensors, and automotive-grade analog products for industrial, automotive, and consumer markets.

The A7987TR belongs to ST's automotive-qualified monolithic buck regulator product line, engineered specifically for 24 V battery systems requiring high input voltage tolerance, functional safety readiness, and thermal resilience in harsh under-hood environments.

FAQ

What is the minimum recommended soft-start capacitor value for A7987TR?

The soft-start capacitor (CSS) is calculated using CSS = (5 µA × TSS) / 0.8 V. For a 10 ms soft-start time, CSS = 62.5 nF. ST recommends ≥100 nF ceramic (X7R) for stability and margin against leakage and tolerance drift. The maximum value is 270 nF to ensure full discharge during EN toggling.

How does the A7987TR achieve 100% duty cycle operation?

The A7987TR achieves near-100% duty cycle by disabling the minimum off-time (TOFFMIN) constraint when VIN approaches VOUT. It then activates an internal low-side MOSFET to discharge the bootstrap capacitor and sustain gate drive, enabling dropout operation down to VIN ≈ VOUT-critical for automotive cold-crank survival.

Can the A7987TR be synchronized to an external clock source?

Yes-the SYNCH pin accepts external TTL/CMOS clock signals from 250 kHz to 1.5 MHz. When driven externally, the internal oscillator locks to the input clock with 180° phase shift. Loop stability must account for PWM gain variation due to ramp amplitude change, so free-running fSW should be set slightly below the external clock frequency.

What is the purpose of the VBIAS pin and how should it be connected?

VBIAS supplies internal analog circuitry to reduce quiescent current at light load. Connect directly to the regulated output (if ≥3 V) or to an auxiliary ≥3 V rail. If unused, tie to GND. When powered from VOUT, bypass with a 1 µF ceramic capacitor to suppress noise coupling into the bias path.