STMicroelectronics L6986H3V3

Overview

L6986H3V3 from STMicroelectronics is a 3.3 V fixed-output, 2 A synchronous step-down switching regulator with 4–38 V input range, peak-current-mode control, and dual operating modes (LCM/LNM). It integrates P-channel high-side and N-channel low-side MOSFETs (R_DS(on) = 180 mΩ / 150 mΩ), features 30 µA quiescent current in low-consumption mode, and delivers precise output voltage supervision via open-drain RST for µC/FPGA reset sequencing in industrial PLCs.

For engineers reviewing the L6986H3V3 datasheet, L6986H3V3 pinout, L6986H3V3 application, or L6986H3V3 equivalent, key selection criteria include its 3.3 V fixed output accuracy (±1.5%), adjustable soft-start, synchronization capability up to 2 MHz, embedded overvoltage protection, and thermal shutdown at 165 °C - all critical for robust 12 V/24 V bus power conversion in noise-sensitive sensor nodes.

Technical Context

The L6986H3V3 implements peak-current-mode control with slope compensation, enabling stable operation across wide duty cycles (0–100%) enabled by its integrated P-channel high-side switch. Its dual-mode architecture supports constant-frequency PWM (LNM) for low-noise operation or pulse-skipping (LCM) for ultra-low IQ (30 µA) at light load.

Internal blocks include a transconductance error amplifier (100 dB gain), programmable soft-start (via SS/INH pin), synchronized clock interface (275–2200 kHz slave range), and ratiometric startup support for multi-rail sequencing. The RST output provides configurable reset delay (via external DELAY capacitor) and active-low assertion when V_OUT falls below user-selected thresholds (e.g., 93% of 3.3 V = 3.069 V).

Key Specifications

Pinout & Package

Package: HTSSOP-16 (exposed pad), RoHS-compliant, thermally enhanced for high-power density designs. Exposed pad must be soldered to SGND/PGND plane for thermal and electrical integrity.

Key Features

Applications

Equivalent & Alternatives

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

Compared with LM61480RQWR and TPS54202HDDCR, the L6986H3V3 uniquely integrates RST-based sequencing, dual LCM/LNM operation for flexible efficiency-noise trade-offs, and 4–38 V input range - making it optimal for industrial 24 V bus systems requiring self-contained, reliable power management.

Availability

L6986H3V3 is available at Aetrix Electronics and suitable for industrial PLCs, decentralized sensor nodes, factory automation edge controllers, and 24 V bus-powered embedded systems requiring stable component supply, long-term lifecycle assurance, and traceable sourcing.

Supply support for L6986H3V3 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, specializing in power management, microcontrollers, and automotive-grade ICs with strong industrial and embedded market focus.

The L6986H series belongs to ST's high-voltage synchronous buck regulator product line, designed specifically for rugged 12 V/24 V industrial power conversion with emphasis on reliability, low-noise operation, and integrated system-level functions like reset supervision and sequencing.

FAQ

What is the recommended soft-start capacitor value for L6986H3V3?

A 200 nF ceramic capacitor is recommended for standard 10 ms soft-start time with internal 4 µA charge current. For ratiometric startup with multiple devices, increase CSS proportionally (e.g., 600 nF for three L6986H3V3 units). Ensure CSS ≤ 67 nF if thermal shutdown recovery must occur within 1 ms, per Equation (2) in DS12905.

How does the VBIAS pin improve efficiency?

VBIAS connects to the regulated 3.3 V output to power part of the internal analog circuitry, reducing current drawn from VIN. When VBIAS = 3.3 V, quiescent current from VIN drops from 70 µA (LCM, no switchover) to 10 µA (LCM with switchover), cutting light-load power loss by ~86% - critical for battery-backed or energy-harvesting nodes.

Can L6986H3V3 operate at 100% duty cycle? How is this achieved?

Yes - the integrated P-channel high-side MOSFET enables true 100% duty-cycle operation, allowing V_OUT to approach V_IN without dropout. This is confirmed by the "Duty cycle = 100% closed loop operation" test condition in Table 5, where peak current limit remains 2.1 A even at maximum duty cycle, ensuring regulation down to V_IN – V_DS(on) × I_LOAD.

What is the maximum allowable DELAY capacitor value for RST timing?

No absolute maximum is specified, but DELAY pin charging current is 1–3 µA (typical 2 µA). To ensure RST release within 100 ms after V_OUT recovery, C_DELAY should be ≤ 100 nF (since V_THD = 1.234 V and ΔV = 1.234 V implies t = C × ΔV / I ≈ 100 nF × 1.234 V / 2 µA ≈ 62 ms). Larger values extend delay but risk violating system reset timing budgets.