Texas Instruments UC3717Q

Overview

UC3717Q from Texas Instruments is a bipolar stepper motor driver IC designed for chopper-controlled current regulation in one winding of 2-phase bipolar permanent magnet or hybrid stepper motors. It delivers ±1A output current, supports 10–45V unregulated motor supply (VM), operates across 0°C to +70°C ambient, and implements half-step/full-step excitation via phase and current-inhibit logic inputs.

For engineers reviewing the UC3717Q datasheet, UC3717Q pinout, UC3717Q application, or UC3717Q equivalent, key selection considerations include its built-in Schottky commutating diodes, dual-bit digital current level selection (100%/60%/19%/inhibit), monostable off-time control (t_OFF = 0.69·R_TC_T), thermal shutdown at +160°C to +180°C, and PLCC-20 package compatibility with microprocessor- or LS-TTL-driven stepper systems.

Technical Context

The UC3717Q integrates an H-bridge output stage using four Darlington transistors with built-in fast-recovery Schottky diodes across source and sink paths-enabling bidirectional current flow and controlled decay during phase reversal. Its current regulation relies on a voltage-divider network feeding three comparators, selected by I0/I1 logic inputs, with threshold voltages of 420mV/250mV/80mV (typ) for 100%/60%/19% current levels.

A monostable circuit triggered by comparator output generates precise off-time (25–35µs at VM=10V), directly controlling average winding current magnitude. Phase input (Schmitt-triggered, noise-immune) toggles complementary transistor pairs (Q1/Q4 vs Q2/Q3) to reverse current direction, while VR analog input enables continuous current adjustment for half-stepping and microstepping.

Key Specifications

Pinout & Package

UC3717Q is housed in a 20-pin Plastic Leaded Chip Carrier (PLCC) package (FN drawing), surface-mount compatible with standard reflow profiles and offering improved thermal performance over DIP variants.

Key Features

Applications

Equivalent & Alternatives

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

Compared with L297+L298 and TB6560AHQ, the UC3717Q offers simpler system-level design for single-winding chopper drive with minimal external components, deterministic off-time control, and robust thermal protection-ideal for cost-sensitive, fixed-step industrial motion control where microstepping is not required.

Availability

UC3717Q is available at Aetrix Electronics and suitable for printer mechanisms, CNC positioning systems, lab automation carousels, and industrial valve actuation requiring stable component supply despite its obsolete status.

Supply support for UC3717Q 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

Texas Instruments is a global semiconductor leader specializing in analog, embedded processing, and power management technologies, with decades of experience in motion control ICs.

The UC3717Q belongs to TI's legacy stepper motor driver family, engineered specifically for cost-effective, robust chopper-based bipolar stepper control in commercial-grade instrumentation and automation equipment.

FAQ

What is the maximum continuous output current supported by the UC3717Q?

The UC3717Q supports ±1A peak output current per winding, as specified in Absolute Maximum Ratings. For continuous operation, derating is required based on thermal conditions: at IM = 500mA and fS = 30kHz, total power dissipation is 1.4–2.1W; at 800mA, it rises to 2.9–3.1W. Actual continuous current must be limited by heatsinking and ambient temperature to keep junction temperature below +150°C. The UC3717Q datasheet confirms this rating applies to the PLCC-20 package under defined test conditions.

Does the UC3717Q require external flyback diodes for stepper motor operation?

No, the UC3717Q does not require external flyback diodes. It integrates fast-recovery Schottky diodes across both source and sink transistors in its internal H-bridge output stage. These diodes provide the necessary current recirculation path during switching transitions and phase reversal, eliminating the need for eight discrete external diodes typically required in discrete H-bridge designs. This feature is explicitly documented in the Functional Description and Features sections of the UC3717Q datasheet.

How does the UC3717Q implement half-step mode, and what pins control it?

The UC3717Q implements half-step mode by alternating between single-winding and dual-winding excitation using its I0/I1 logic inputs and VR analog reference input. I0 and I1 (pins 9 and 11) select discrete current levels (100%, 60%, 19%, or inhibit), while VR (pin 11) enables continuous current adjustment to boost torque in single-winding states and smooth torque ripple. The phase input (pin 10) sequences direction changes in coordination with current inhibit signals. This behavior is confirmed in the Applications section and Figure 12 of the UC3717Q datasheet.

What is the purpose of the Timing pin (pin 2) on the UC3717Q?

The Timing pin (pin 2) on the UC3717Q connects to an external RC network (RT and CT) that sets the monostable off-time (t_OFF) according to t_OFF = 0.69·R_TC_T. This off-time determines the chopper frequency and governs how rapidly current decays in the motor winding during each cycle. A shorter t_OFF increases chopper frequency and reduces average current; longer t_OFF lowers frequency and raises current. This relationship is defined in the Electrical Characteristics and Functional Description sections of the UC3717Q datasheet.

Is the UC3717Q pin-compatible with other members of the UC37xx family, such as UC3717N?

No, the UC3717Q is not pin-compatible with UC3717N. UC3717Q uses a 20-pin PLCC (FN) package with distinct pinout-including dedicated Phase (pin 10), VR (pin 11), and Emitters (pin 19) functions-while UC3717N is a 16-pin PDIP (N) device with different pin assignments (e.g., N/C on pins 1,6,10,12,15,16). The Connection Diagrams and PACKAGE PIN FUNCTION tables in the UC3717Q datasheet confirm these structural differences. Interchangeability requires board redesign.