STMicroelectronics L9935

Overview

L9935 from STMicroelectronics is a two-phase bipolar stepper motor driver IC with dual 1.1 A full-bridge outputs, integrated chopping current regulation, SPI serial interface, and comprehensive protection (short-circuit, open-load, overtemperature pre-alarm). It operates up to 24 V supply and draws only 40 µA in standby, targeting motion control in industrial automation, printer mechanisms, and precision positioning systems.

For engineers reviewing the L9935 datasheet, L9935 pinout, L9935 application, or L9935 equivalent, key selection criteria include chopper current setting resolution (four discrete levels via SPI bits), controlled output voltage slew rates for EMI reduction, thermal pre-alarm at 130–160 °C, and dual full-bridge timing coordination via offset-phase oscillator synchronization.

Technical Context

The L9935 implements two independent full-bridge drivers (OUTA1/OUTA2 and OUTB1/OUTB2) with internal DMOS power stages and external current-sense resistors (SRA/SRB) enabling precise PWM-based current regulation. Each bridge supports four programmable current limits (0 mA, 60 mA, 550 mA, 900 mA typ.) selected via SPI-configurable bits.

Its protection architecture includes short-to-VS detection (triggered within 2–5 µs at 1.5× nominal current), open-load diagnosis, and thermal pre-alarm at 130–160 °C followed by shutdown at 160–200 °C. The offset-phase chopper oscillator reduces supply current ripple by half compared to synchronous chopping.

Key Specifications

Pinout & Package

Package: PowerSO-20 - thermally enhanced surface-mount package with exposed die pad for junction-to-case thermal resistance of 5 °C/W, optimized for high-current motor drive applications requiring efficient heat dissipation.

Key Features

Applications

Equivalent & Alternatives

The following parts are listed as comparable options for similar two-phase stepper motor driver applications.

Compared with TB6600HG and DRV8825, the L9935 delivers unique integration of diagnostic flags, offset-phase chopper EMI reduction, and thermal pre-alarm-making it optimal for industrial motion systems requiring field reliability, regulatory compliance, and minimal external component count.

Availability

L9935 is available at Aetrix Electronics and suitable for industrial CNC positioning, automated document feeder mechanisms, lab equipment stage control, and valve actuation in analytical instruments requiring stable component supply and long-term lifecycle support.

Supply support for L9935 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, motion control, and automotive-grade ICs with broad industrial qualification coverage.

The L9935 belongs to ST's dedicated motor driver product line, engineered for robust, self-protected stepper control in harsh environments-emphasizing integrated diagnostics, thermal resilience, and EMI-aware design for factory automation and precision instrumentation.

FAQ

What is the minimum external sense resistor value supported for full-scale 900 mA current regulation?

The L9935 achieves its maximum 900 mA typical current limit with a 0.33 Ω sense resistor (SRA/SRB), yielding ~300 mV drop at regulation threshold. Lower values (e.g., 0.22 Ω) are permissible but reduce current resolution and increase power loss in the resistor; ST specifies 0.33 Ω as the recommended value for full-scale operation per Table 6 and Figure 4.

How does the offset-phase chopper reduce electromagnetic emissions?

The L9935 uses two chopper oscillators phase-shifted by 180°, causing the two full bridges to alternate their PWM switching edges. This cancels common-mode supply current harmonics, halving peak ripple amplitude versus synchronized chopping-directly lowering conducted EMI and relaxing input filter requirements per Figure 7 and Section 5.2.5.

Can the L9935 drive unipolar stepper motors?

No-the L9935 is designed exclusively for bipolar stepper motors. Its dual full-bridge topology requires four-wire (or six-wire with center taps unused) bipolar windings. Unipolar motors require single-polarity drive per phase and are incompatible with the L9935's complementary output switching and current-sense architecture.

What happens to the error flag after detecting an open-load condition?

Upon open-load detection, the L9935 asserts the open-drain ERROR flag and holds it active until a new SPI command byte is written to the device. A rising edge on CSN resets the flag only if no other active faults (e.g., overtemperature or short-circuit) persist-enabling deterministic fault clearing per Section 5.3 and Table 8.