STMicroelectronics L6506D

Overview

L6506D from STMicroelectronics is a linear current controller IC for bipolar/unipolar stepper motor windings, featuring dual PWM chopper channels, internal oscillator (5–70 kHz), TTL-compatible logic I/O, ±20 mV input offset voltage over temperature, and synchronization capability via SYNC pin. It interfaces with bridge drivers (e.g., L298) or discrete power stages to implement constant-current microstepping drives in motion control systems.

For engineers reviewing the L6506D datasheet, L6506D pinout, L6506D application, or L6506D equivalent, key selection criteria include chopper frequency programmability via external RC, independent winding current programming using VREF and sense resistors, thermal resistance (100 °C/W for SO20), and synchronization support for multi-axis coordinated motion.

Technical Context

The L6506D integrates two independent current-sensing comparators, flip-flop-based PWM choppers, and a programmable RC oscillator with 1/3–2/3 VCC thresholds and 1 kΩ ±30% internal discharge resistor. Each chopper channel accepts separate sense inputs (VIN range: –0.3 to 3 V) and resets when sensed voltage equals VREF.

It supports TTL-level logic interface (VIH = 2 V, VOL = 0.4 V @ 4 mA), operates from 4.5–7 V supply, draws 25 mA quiescent current at 7 V, and enables synchronized multi-chip operation by routing the master's oscillator output to slave SYNC pins while grounding unused R/C networks.

Key Specifications

Pinout & Package

Available in SO20 (20-pin small outline) and DIP18 (18-pin dual in-line) packages. SO20 package measures 12.6 × 7.4 mm with 1.27 mm pitch; DIP18 measures 23.24 × 8.5 mm with 2.54 mm pitch.

Key Features

Applications

Equivalent & Alternatives

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

Compared with TMC2100-LA and DRV8811, the L6506D offers unmatched flexibility in bridge selection (L298, L293, discrete MOSFETs), deterministic timing via RC oscillator, and proven multi-axis synchronization - making it ideal for industrial-grade open-loop stepper systems requiring long-term reliability and field serviceability.

Availability

L6506D is available at Aetrix Electronics and suitable for industrial CNC controllers, medical infusion pumps, 3D printer motion subsystems, and automated test equipment requiring stable component supply and long-lifecycle support.

Supply support for L6506D 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 analog, mixed-signal, power, and microcontroller products for industrial, automotive, and consumer markets.

The L6506D belongs to ST's motor control analog IC portfolio, developed specifically to provide robust, programmable current regulation for stepper motor drives in cost-sensitive, high-reliability industrial motion systems.

FAQ

What is the minimum external RC value needed to achieve 70 kHz oscillator frequency?

The minimum oscillator frequency equation is f = 1/(0.69·R·C). To reach 70 kHz, R·C must equal ≈20.7 ns. With R ≥10 kΩ per datasheet, the smallest practical C is 2.07 pF - but parasitic capacitance dominates below 10 pF. ST recommends R = 10 kΩ and C = 220 pF for 70 kHz, verified in Figure 1 application circuit.

Can L6506D drive both bipolar and unipolar stepper motors?

Yes - the L6506D controls current in individual windings regardless of topology. For bipolar motors, it pairs with H-bridge drivers (e.g., L298); for unipolar motors, it interfaces with Darlington arrays (e.g., L7150) or discrete NPN transistors. Independent REF A/B inputs allow asymmetric current programming per phase.

How does the SYNC function eliminate beat frequencies in multi-axis systems?

When multiple L6506D devices operate asynchronously, their independent oscillators drift, causing periodic constructive/destructive interference in motor torque. Connecting one device's oscillator output to others' SYNC pins forces identical chopper timing across all axes - eliminating torque modulation at difference frequencies and ensuring smooth coordinated motion.

Is an external VREF required, or does L6506D provide an internal reference?

The L6506D provides an internal 1.4 V reference at the VREF pin (Pin 19), usable directly for basic applications. However, external precision references (e.g., REF5025) can be applied to REF A/B pins (Pins 4/5) to improve current accuracy to ±0.5% - critical for closed-loop hybrid stepper systems requiring repeatable torque output.