STMicroelectronics L6983IQTR

Overview

L6983IQTR from STMicroelectronics is a synchronous isolated buck (iso-buck) DC-DC converter IC designed for primary-side regulation in transformer-coupled isolated power supplies. It operates from 3.5 V to 38 V input, delivers up to 4.5 A peak primary current, supports 200 kHz–1 MHz programmable switching frequency, and eliminates optocoupler need via precise primary-side voltage feedback. It targets gate drive supplies for IGBTs/SiC MOSFETs in EV on-board chargers and traction inverters.

For engineers reviewing the L6983IQTR datasheet, L6983IQTR pinout, L6983IQTR application, or L6983IQTR equivalent, key selection criteria include its forced PWM peak current mode control, 390 ns current-sense blanking time for transformer leakage immunity, QFN16 (3×3 mm) thermal performance (R_{th_JA} = 42 °C/W), and integrated soft-start with tracked secondary output ramp-up.

Technical Context

The L6983IQTR implements a peak current mode controller with fixed-frequency forced PWM operation, enabling bidirectional energy transfer during both high-side and low-side conduction - critical for synchronized soft-start of isolated outputs. Its internal transconductance error amplifier features an integrated compensation network and references a stable 0.85 V FB threshold across –40 °C to +125 °C.

It includes pulse-by-pulse high-side/low-side current sensing for constant-current protection, 390 ns blanking time to suppress transformer leakage-induced oscillations, and dual-threshold EN/CLKIN pin supporting both enable/disable control and external clock synchronization from 200 kHz to 1 MHz. The device also integrates spread spectrum dithering (±5% Δf) for EMC improvement.

Key Specifications

Pinout & Package

Supplied in a thermally enhanced QFN16 (3 mm × 3 mm, 0.5 mm pitch) package with exposed pad connected to AGND/PGND for low thermal resistance (R_{th_JA} = 42 °C/W).

Key Features

Applications

Equivalent & Alternatives

The following parts are listed as comparable options for similar isolated buck controller applications.

Compared with UCC28911DR and MAX256ASA+, the L6983IQTR uniquely integrates synchronous iso-buck control, primary-side regulation, and transformer leakage resilience - making it the only solution that delivers regulated isolated output without optocouplers while supporting high-current gate drive sequencing.

Availability

L6983IQTR is available at Aetrix Electronics and suitable for electric vehicle on-board chargers, traction inverter gate drive supplies, and industrial isolated sensor interfaces requiring stable component supply, long-term lifecycle support, and AEC-Q100-compliant sourcing.

Supply support for L6983IQTR 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 power management, automotive ICs, and industrial control solutions with over 45 years of analog/mixed-signal design heritage.

The L6983I belongs to ST's high-voltage isolated DC-DC controller product line, engineered specifically for next-generation EV/HEV power systems requiring compact, reliable, and optocoupler-free isolated bias rails.

FAQ

What is the purpose of the VINLDO pin on the L6983IQTR?

The VINLDO pin supplies the internal LDO regulator that powers analog circuitry. It must be connected to VIN through an RC filter (e.g., 0.1 kΩ + 1 µF) to attenuate high-frequency noise from the main input rail. This separation improves regulation accuracy and reduces susceptibility to input ripple, especially critical in noisy automotive environments.

Can the L6983IQTR operate without an external bootstrap capacitor?

No. The BOOT pin requires a 100 nF ceramic capacitor connected to the SW node to provide gate drive voltage for the high-side NMOS. Omitting this capacitor prevents proper high-side switching, causing immediate failure of the power stage and potential damage due to shoot-through or uncontrolled duty cycle.

How does the L6983IQTR achieve optocoupler-less regulation?

It uses a precision 0.85 V internal reference and peak current mode control to regulate the primary-side output voltage directly. The secondary output voltage is derived solely from the transformer turns ratio and remains tightly coupled to the primary output - eliminating need for secondary-side feedback or optocouplers while maintaining ±1.5% overall output accuracy.

What is the minimum recommended output capacitance for stable operation?

The datasheet specifies stability with ≥2 µF low-ESR ceramic output capacitance. For production designs, ST recommends three 22 µF X7R ceramics (total 66 µF) to ensure sufficient hold-up time, reduce ripple under dynamic load steps, and maintain phase margin across temperature and aging - especially critical in OBC auxiliary rail applications.