STMicroelectronics L297/1

Overview

L297/1 from STMicroelectronics is a dedicated stepper motor controller IC for bipolar and unipolar two-phase/four-phase motors, supporting half-step, normal (two-phase-on), and wave (one-phase-on) drive modes with on-chip dual PWM chopper current regulation, 5 V supply operation, and programmable peak current via Vref (0–3 V). It interfaces directly with L298N or discrete power stages in motion control systems for CNC equipment and precision positioning.

For engineers reviewing the L297/1 datasheet, L297/1 pinout, L297/1 application, or L297/1 equivalent, key selection considerations include chopper control mode (CONTROL pin logic), synchronous multi-controller configuration (SYNC/OSC pins), phase sequencing behavior (HALF/FULL state dependency), and load current sensing architecture (dual SENS1/SENS2 inputs with common Vref).

Technical Context

The L297/1 integrates a state-machine translator generating ABCD phase sequences and a dual independent PWM chopper with internal oscillator (f ≈ 1/(0.69·RC)), comparator-based current limiting, and selectable chopping action on either phase outputs (ABCD) or inhibit lines (INH1/INH2) via the CONTROL input. Its home state is fixed at ABCD = 0101, and direction reversal is fully synchronized without timing constraints.

Reset (active-low) forces immediate return to state 1; step advancement occurs on rising edge of CLOCK; CW/CCW input changes rotation direction asynchronously. The translator's mode selection depends not only on HALF/FULL logic level but also on current state parity-full-step requires odd states for two-phase-on, even states for one-phase-on-enabling precise waveform control without external sequencing logic.

Key Specifications

Pinout & Package

Package: 20-pin Dual In-line Package (DIP20), 0.3-inch body width, through-hole mounting compatible with standard PCB layouts and prototyping breadboards.

Key Features

Applications

Equivalent & Alternatives

The following parts are listed as comparable options for similar stepper motor controller applications.

Compared with TB6560AHQ and UCN5804B, the L297/1 offers unique flexibility in chopper targeting (phase vs. inhibit lines), explicit hardware homing (HOME pin), and state-aware drive mode selection - making it optimal for legacy-compatible, medium-power bipolar systems requiring deterministic timing and thermal management.

Availability

L297/1 is available at Aetrix Electronics and suitable for industrial CNC positioning, medical infusion pumps, automated laboratory analyzers, and 3D printer extruder control requiring stable component supply and long-term obsolescence management.

Supply support for L297/1 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 ICs with broad manufacturing scale and AEC-Q100/IEC 60730 compliance capabilities.

The L297 belongs to ST's legacy motor control product line, designed specifically for cost-effective, reliable open-loop stepper actuation in industrial automation and precision instrumentation where microcontroller offload and analog current regulation are critical.

FAQ

What is the function of the CONTROL pin on the L297/1?

The CONTROL pin selects whether the internal PWM chopper regulates current on the phase outputs (A/B/C/D) or the inhibit lines (INH1/INH2). When CONTROL = high, chopping occurs on phase lines - preferred for bipolar bridges like L298N to reduce sense resistor losses. When CONTROL = low, chopping targets INH1/INH2 - optimal for unipolar drivers or fast current decay requirements. This dual-mode capability is confirmed in the "Circuit Operation" section of the official ST datasheet (Rev 11, p.3).

Can the L297/1 drive a unipolar stepper motor?

Yes, the L297/1 supports four-phase unipolar stepper motors using wave or full-step modes. In unipolar configurations, the chopper typically acts on INH1/INH2 (CONTROL = low) to control current decay in the center-tapped windings. The IC does not integrate power transistors, so external Darlington arrays (e.g., ULN2003) or discrete transistors are required - as explicitly stated in the "Circuit Operation" and "Application Information" sections (pp.3, 8).

How does the HALF/FULL input determine drive mode?

The HALF/FULL input alone does not fully define the drive mode: when HIGH, it selects half-step; when LOW, the translator selects normal (two-phase-on) if in an odd-numbered state (1,3,5,7) or wave (one-phase-on) if in an even-numbered state (2,4,6,8). This state-dependent behavior is documented in the "MOTOR DRIVING PHASE SEQUENCES" section (pp.4–5) and enables three distinct excitation patterns using a single control line.

What is the purpose of the SYNC and OSC pins in multi-L297 systems?

SYNC is the chopper oscillator output; OSC is the oscillator timing node. In synchronized multi-controller setups, all SYNC pins are tied together, the RC network is placed only on one device's OSC pin, and OSC on all others is grounded. This ensures identical chopper frequencies across devices, eliminating beat frequencies and current ripple - a requirement explicitly detailed in Figure 3 ("Synchronising L297s", p.8) and the "Circuit Operation" text (p.3).