SX1508IULTRT - 8-bit I2C GPIO Expander with LED Driver | Semtech
MPN: SX1508IULTRT ✓ Active| Qty | Unit Price | Extended |
|---|---|---|
| 1 | $2.1 | $2.10 |
| 10 | $1.89 | $18.90 |
| 100 | $1.62 | $162.00 |
| 500 | $1.38 | $690.00 |
| 1,000 | $1.15 | $1,150.00 |
| 3,000 | $0.95 | $2,850.00 |
SX1508IULTRT Overview
An I/O expander is a type of interface IC that increases the number of general-purpose input/output pins available to a host microcontroller over a serial bus such as I2C. In the broader taxonomy it sits under interface ICs -> peripheral expanders -> GPIO expanders -> integrated circuits. The SX1508IULTRT belongs to Semtech's world-leading ultra-low-voltage level-shifting GPIO portfolio, enabling direct connection of low-voltage controllers (down to 1.2 V) to higher-voltage peripherals (up to 5.5 V tolerant) without external translator ICs.
Key features include 8 individually programmable I/O channels, configurable as inputs, push-pull outputs, or open-drain outputs with internal pull-up resistors; per-pin PWM (4 to 124 duty steps at 2 Hz to 2 kHz) for LED brightness control; programmable debounce and latch registers; interrupt output with masking; and an I2C address range selectable via two external pins. The keypad engine auto-scans up to 64 keys without host intervention, offloading the MCU.
Internally, the device uses a CMOS process with on-chip charge-pump-free level shifting and integrates 8-bit PWM timers, a debounce filter block, and a fully static I2C slave. It supports standard (100 kHz), fast (400 kHz), and high-speed I2C modes, with hardware-configurable addresses allowing up to 4 SX1508s on a single bus for 32 additional GPIOs.
Typical applications include keypads and button matrices in handheld and IoT products, LED status indication and backlight control, level shifting between low-voltage microcontrollers and 3.3 V or 5 V peripherals, expanding the limited GPIO count on small-pincount MCUs, and battery-powered devices where ultra-low quiescent current matters. The 3x3 mm QFN-UT package suits space-constrained wearables and sensor nodes.
When designing with this part, observe the 1.2 V minimum VCC and provide a decoupling capacitor close to the supply pin; enable the internal pull-ups only when external pull-ups are not present to avoid contention. The interrupt pin must be serviced before the next keypad event, and unused I/O lines should be configured as outputs to minimize quiescent draw.
This page synthesizes distributor pricing, drop-in alternatives from the Semtech SX150x family and cross-brand equivalents, plus practical design notes that extend beyond the manufacturer datasheet.
Drop-in alternatives for SX1508IULTRT — same package, pin-to-pin compatible. Different-package parts requiring PCB rework are excluded.
Variants in this series
Same-series models that are drop-in compatible with SX1508IULTRT (same form factor and footprint) — differing in I2C Clock Frequency, Interrupt Output, Package.
Quick Comparison Tool — Select alternative parts for side-by-side comparison:
SX1509IULTRT
✅ Drop-In📋 Reference alternative (not in catalog)
SX1507IULTRT
✅ Drop-In📋 Reference alternative (not in catalog)
SX1508EVK
✅ Drop-In📋 Reference alternative (not in catalog)
SX1508IULTRT Maximum Ratings & Electrical Characteristics
| Interface Type | I2C (Standard / Fast / High-Speed) |
| Number of I/O | 8 |
| I2C Clock Frequency | 400 kHz |
| Supply Voltage (VCC) | 1.2 V to 3.6 V |
| I/O Voltage Tolerance | Up to 5.5 V |
| Output Drive | 8 mA per pin (sink/source) |
| LED PWM Frequency | 2 Hz to 2 kHz |
| LED PWM Resolution | 4 to 124 duty steps |
| Keypad Engine | Up to 8x8 matrix, auto-scan |
| Interrupt Output | Active-low INT with masking |
| Programmable Pull-ups | Yes (internal, per pin) |
| Selectable I2C Addresses | 4 (via ADDR0/ADDR1 pins) |
| Operating Temperature | -40 C to +85 C |
| Package | 20-QFN-UT (3x3 mm) Exposed Pad |
| Packaging | Tape & Reel (TR) |
| Mounting Type | Surface Mount |
| RoHS Status | Compliant |
SX1508IULTRT Pin Configuration
| Pin 1 | GND — Ground reference |
| Pin 2 | SCL — I2C clock input |
| Pin 3 | SDA — I2C data (bidirectional, open-drain) |
| Pin 4 | ADDR0 — I2C address select bit 0 |
| Pin 5 | ADDR1 — I2C address select bit 1 |
| Pin 6 | INT — Interrupt output (active low, open-drain) |
| Pin 7 | RESET — Active-low hardware reset (tie to VCC if unused) |
| Pin 8 | IO0 — Bidirectional GPIO 0 / LED driver 0 / Keypad row 0 |
| Pin 9 | IO1 — Bidirectional GPIO 1 / LED driver 1 / Keypad row 1 |
| Pin 10 | IO2 — Bidirectional GPIO 2 / LED driver 2 / Keypad row 2 |
| Pin 11 | IO3 — Bidirectional GPIO 3 / LED driver 3 / Keypad row 3 |
| Pin 12 | IO4 — Bidirectional GPIO 4 / LED driver 4 / Keypad col 0 |
| Pin 13 | IO5 — Bidirectional GPIO 5 / LED driver 5 / Keypad col 1 |
| Pin 14 | IO6 — Bidirectional GPIO 6 / LED driver 6 / Keypad col 2 |
| Pin 15 | IO7 — Bidirectional GPIO 7 / LED driver 7 / Keypad col 3 |
| Pin 16 | VCC — Positive supply input (1.2 V to 3.6 V) |
| Pin 17 | NC — Not connected (per datasheet) |
| Pin 18 | NC — Not connected (per datasheet) |
| Pin 19 | NC — Not connected (per datasheet) |
| Pin 20 | EP — Exposed thermal pad (connect to GND) |
Typical Applications
SX1508IULTRT is suitable for 7 applications: Handheld Device Keypads, LED Status Indicators and Backlights, Level Shifting Between 1.2 V MCUs and 5 V Peripherals, IoT Sensor Hubs and Wearable Devices, Industrial Control Panel GPIO Expansion, Battery-Powered Medical Devices, Automotive Infotainment Button Panels.
Handheld Device Keypads
The SX1508IULTRT drives 8x8 key matrix scanning with on-chip debounce and ghost-key prevention, eliminating host MCU polling for up to 64 keys. Operating from 1.2 V to 3.6 V, it suits handheld terminals, remote controls, and security panels powered by coin cells or Li-ion batteries; the integrated keypad FIFO holds events until the MCU wakes, enabling deep-sleep current below 1 uA in the host.
Recommended
LED Status Indicators and Backlights
Eight independent PWM channels drive status LEDs and backlights from 2 Hz to 2 kHz with 4 to 124 duty steps, eliminating host CPU timer overhead. The SX1508IULTRT per-pin PWM supports smooth fade-in/fade-out effects with linear or logarithmic curves, and 8 mA sink/source drive enables direct LED connection with a single series resistor. This is ideal for appliance front panels, industrial HMIs, and IoT devices with multi-color indicators.
Recommended
Level Shifting Between 1.2 V MCUs and 5 V Peripherals
With 1.2 V VCC and 5.5 V tolerant I/O pins, the SX1508IULTRT bridges modern low-voltage microcontrollers to legacy 3.3 V or 5 V sensors, displays, and actuators without external translator ICs. Each of the 8 I/O lines is independently configurable as input, push-pull, or open-drain with optional pull-up, simplifying bidirectional level translation. This reduces BOM cost and PCB area in mixed-voltage designs.
Recommended
IoT Sensor Hubs and Wearable Devices
The 3x3 mm QFN-UT package and 1.2 V operation make the SX1508IULTRT suited for wearables, fitness bands, and IoT sensor hubs where PCB area is at a premium and battery life is critical. With I2C addressing for up to 4 devices per bus, designers can scale to 32 GPIOs while the host MCU sleeps. The exposed pad aids thermal dissipation in always-on edge devices.
Recommended
Industrial Control Panel GPIO Expansion
Industrial HMIs, PLCs, and control panels often need more GPIOs than the host MCU offers; the SX1508IULTRT provides 8 rugged I/O lines with industrial temperature grade (-40 C to +85 C) and I2C isolation-friendly packaging. The integrated keypad engine supports 4x4 or 8x4 membrane keypads common on factory-floor panels, and the I2C interface pairs with digital isolators like Si864x for high-voltage safety isolation.
Recommended
Battery-Powered Medical Devices
Patient monitors, portable diagnostic kits, and infusion pumps benefit from the SX1508IULTRT's 1.2 V VCC and integrated keypad/LED engine that lets the host MCU remain in deep sleep until an event occurs. The RoHS-compliant 3x3 mm QFN-UT package meets space-constrained medical PCB layouts, and the I2C bus accommodates multiple devices on a single isolated rail, simplifying medical-grade safety design.
Recommended
Automotive Infotainment Button Panels
The SX1508IULTRT can drive 8x8 button matrices for HVAC, infotainment, and steering-wheel controls in vehicles; its industrial temperature grade and I2C interface simplify integration with automotive MCUs over CAN-translated buses. Note that the SX1508 is not AEC-Q100 qualified - for safety-critical automotive applications, prefer AEC-Q100-qualified GPIO expanders from NXP or Texas Instruments in similar QFN packages.
Recommended
Recommended Products Summary
Engineering reference data for SX1508IULTRT — comparison, design guidance, and compliance information.
Selection Guide
Comparison with Alternatives
| Parameter | This Product | SX1509IULTRT | SX1507IULTRT |
|---|---|---|---|
| Package | 20-QFN-UT (3x3 mm) | 20-QFN-UT (3x3 mm) - same | 20-QFN-UT (3x3 mm) - same |
| Brand | Semtech | Semtech | Semtech |
| Number of I/O | 8 | 16 | 4 |
| Supply Voltage | 1.2 V to 3.6 V | 1.2 V to 3.6 V | 1.2 V to 3.6 V |
| I2C Clock | 400 kHz | 400 kHz | 400 kHz |
| LED PWM Engine | Yes (8 channels) | Yes (16 channels) | Yes (4 channels) |
| Keypad Engine | Yes (8x8) | Yes (8x8) | Yes (4x4) |
| Output Drive Current | 8 mA | 8 mA | 8 mA |
| I/O Voltage Tolerance | 5.5 V | 5.5 V | 5.5 V |
| Lifecycle Status | Active | Active | Active |
Key Differentiators
- Lowest voltage level-shifting GPIO expander (vs NXP PCA9538PW)
- Integrated LED PWM driver and keypad engine (vs Microchip MCP23008T-E/ML)
- Compact 3x3 mm QFN-UT footprint (vs SX1509IULTRT (4x4 mm package))
Design Notes
The SX1508IULTRT operates from 1.2 V to 3.6 V on VCC; place a 0.1 uF decoupling capacitor within 5 mm of the VCC pin and a bulk 1 uF to 10 uF capacitor nearby. The exposed pad must be soldered to a ground plane with at least 4 thermal vias to a secondary ground layer for stable operation. Power-on sequence is not critical since I/Os remain tri-stated until configuration.
Route SCL and SDA as a differential pair if possible, keeping them short (<50 mm) and away from switching nodes. Place 2.2 kohm to 10 kohm pull-ups on SCL and SDA to VCC; the exact value depends on bus capacitance and desired rise time. The INT pin should have its own pull-up resistor if not provided by the host MCU.
Do not float the RESET pin; tie it to VCC through a 100 kohm resistor if no host reset control is needed. Do not exceed 5.5 V on any IO pin even when VCC is below 3.6 V - the IO lines tolerate 5.5 V but exceeding it will permanently damage the device. When using internal pull-ups, disable them if external pull-ups are present to avoid contention.
For long I2C buses or systems with multiple SX1508 devices, add bus repeaters or reduce clock frequency below 100 kHz to mitigate ringing. The I2C slave on the SX1508 holds SDA low briefly during acknowledge cycles - allow sufficient clock-stretching margin in the host MCU driver.
Compliance Information
RoHS compliant per Semtech product page. NOT AEC-Q100 qualified - for automotive applications choose AEC-Q100-qualified GPIO expanders from NXP or TI in similar QFN-20 footprint.
