The STMicroelectronics STM8S903K3U3 is an 8-bit microcontroller from the STM8S family, built around the STM8 core and clocked at 16 MHz.
Housed in a 32-UFQFN with an exposed pad (5x5 mm body), the part is surface-mount and compact.
STM8S903K3U3 STM8S 8-bit MCU, 16 MHz, 8 KB Flash
MPNSTM8S903K3U3
Active
STMicroelectronics STM8S903K3U3, STM8S series 8-bit MCU, 16 MHz core, 8 KB Flash, 1 KB RAM, 640 B EEPROM, 2.95V-5.5V supply, -40°C to 125°C, 28 I/O, 32-UFQFPN (5x5 mm), Tray.
$1.2459Ref. price · indicative, final on quote
Independent supplier — new & surplus stockAuthenticity-screened · ESD-safe packingListing updated Jul 2026
Specifications
| Parameter | Value |
|---|---|
| Series | STM8S |
| Mounting | Surface Mount |
| Oscillator type | Internal |
| Program memory type | FLASH |
| Voltage - supply (Vcc (Vdd)) | 2.95V ~ 5.5V |
| Operating temperature | -40°C~125°C(TA) |
| Speed | 16MHz |
| Package | Tray |
| RAM size | 1K x 8 |
| Core size | 8-Bit |
| EEPROM size | 640 x 8 |
| Peripherals | Brown-out Detect/Reset, POR, PWM, WDT |
| Connectivity | I²C, IrDA, LINbus, SPI, UART/USART |
| Number of i (O) | 28 |
| Core processor | STM8 |
| Case | 32-UFQFN Exposed Pad |
| Data converters | A/D 7x10b |
| Program memory size | 8KB (8K x 8) |
Product details
Frequently asked questions
What is the closest pin-compatible alternative to STM8S903K3U3 in this component family?
Within the STM8S903 series, devices with the same package and pinout differ mainly in Flash density. The STM8S903K3U3 carries 8 KB Flash; a higher-density sibling like the STM8S903F3 (8 KB, same pinout) or the STM8S903K3 (also 8 KB) may be cross-shopped. For a different Flash size in the same footprint, check the STM8S903x3/x6 variants — the datasheet's ordering information table lists the exact memory options.
How to program STM8S903K3U3?
Programming uses ST's SWIM (Single Wire Interface Module) protocol, accessible through the SWIM pin. Standard tools include the ST-Link programmer/debugger and ST Visual Programmer software.