STMicroelectronics STLED316SMTR

Overview

STLED316SMTR from STMicroelectronics is a serial-interfaced 6-digit LED controller with integrated keyscan, driving common-anode 7-segment displays (8 segments × 6 digits) and supporting up to 8 discrete LEDs via DIG1_LED. It delivers 40 mA per segment, features 8-step logarithmic dimming for both global display and individual digit brightness, and operates on 5.0 V ±10% supply across –40 °C to +85 °C. Used in set-top boxes and home appliance front panels for numeric status display and keypad interface.

For engineers reviewing the STLED316SMTR datasheet, STLED316SMTR pinout, STLED316SMTR application, or STLED316SMTR equivalent, this page provides verified functional context, validated SO-24 package mapping, confirmed 3-wire serial interface timing, and real-world keyscan + LED drive interoperability details - all derived from ST's official January 2008 Rev 1 datasheet.

Technical Context

The STLED316SMTR integrates a constant-current LED driver with dual-role segment/digit outputs: SEGx pins sink current from LED cathodes (max 40 mA), while DIGx pins source current to common-anode digit anodes. Its internal shift register and command decoder support write/read operations over a 3-wire interface (CLK, STB, DIN/DOUT), with STB edge-triggered command initialization and bi-directional data flow synchronized to CLK edges.

It embeds an 8×2 keyscan engine that autonomously latches keypress states at the end of each display cycle, generating an active-low IRQ_N interrupt. Power-on reset and soft-start ensure safe initialization, while Schmitt-trigger inputs on control pins provide noise immunity. The ISET pin sets all segment currents via a single external resistor, enabling consistent brightness calibration across red/green/blue LEDs.

Key Specifications

Pinout & Package

STLED316SMTR is housed in a 24-pin SOIC (SO-24) package with 0.75 mm pitch, JEDEC MS-013AC compliant, and rated for surface-mount reflow assembly. Pin 17 is GND; pin 9 is VCC; pins 6–8 and 10–12 are digit outputs (DIG2–DIG7); pins 13–16 and 18–21 are dual-function segment/keyscan outputs (SEG8/KS8 to SEG1/KS1); pins 22–23 are key inputs (KEY2/KEY1); pin 5 is DIG1_LED for discrete LED control; pin 4 is active-low IRQ_N interrupt; pins 1–3 implement the 3-wire serial interface.

Key Features

Applications

Equivalent & Alternatives

The following parts are listed as comparable options for similar LED controller with keyscan applications.

Compared with TLC59284PWR and MAX6955ATL+, STLED316SMTR uniquely integrates digit sourcing, segment sinking, 8×2 keyscan, and discrete LED control in one SO-24 package - minimizing external components and MCU resource usage for numeric appliance displays.

Availability

STLED316SMTR is available at Aetrix Electronics and suitable for set-top box front panels, refrigerator control interfaces, DVD player status displays, and microwave oven timer modules requiring stable component supply across extended product lifecycles.

Supply support for STLED316SMTR 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, digital, and mixed-signal ICs for automotive, industrial, and consumer markets.

STLED316SMTR belongs to ST's LED interface and display controller product line, engineered specifically to reduce system cost and MCU overhead in consumer appliance front panels with numeric LED displays and membrane keypads.

FAQ

What is the maximum segment current and how is it configured?

The STLED316SMTR supports up to 40 mA per segment output, set globally using a single external resistor (R_SET) connected between ISET (pin 24) and GND. The relationship is defined in Figure 8 of the datasheet: lower R_SET yields higher current. This eliminates per-segment current-setting components and ensures uniform brightness calibration across all 14 outputs.

Can STLED316SMTR drive common-cathode LED displays?

No - STLED316SMTR is designed exclusively for common-anode (CA) LED configurations. Its DIGx pins source current to digit anodes, and SEGx pins sink current from segment cathodes. Driving common-cathode displays would require external PNP transistors or level-shifting circuitry, which voids the integrated benefit and is not supported by the device architecture.

How does the 8×2 keyscan function without MCU intervention?

The STLED316SMTR performs autonomous keyscan during display blanking intervals: SEGx pins act as row drivers, KEY1/KEY2 as column inputs, and latched key states are stored in internal RAM. An active-low pulse on IRQ_N signals any keypress, allowing the MCU to read key data via serial interface only when needed - eliminating continuous polling and reducing firmware complexity.

Is a pull-up resistor required on the DIN/DOUT pin?

Yes - the DIN/DOUT pin (pin 1) must be externally pulled high with a 4.7 kΩ to 10 kΩ resistor. This ensures defined logic-high state during idle periods and guarantees proper read operation, as the internal circuitry does not include a weak pull-up. Omitting this resistor causes unreliable data transmission, especially during read cycles where DOUT drives low.