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STMicroelectronics STM8S105K4U6A — Microcontrollers & Processors (MCU / MPU / DSP)

STM8S105K4U6A 8-bit MCU, 16 MHz, 16 KB Flash, 32-UFQFPN

MPNSTM8S105K4U6A
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STMicroelectronics STM8S105K4U6A, STM8S series, 8-bit MCU, 16 MHz, 16 KB Flash, 2K x 8 RAM, 1K x 8 EEPROM, 2.95V to 5.5V, I²C/SPI/UART/LIN, 25 I/O, -40°C to 85°C, 32-UFQFPN (5x5 mm).

$2.5100Ref. price · indicative, final on quote
STMicroelectronics STM8S105K4U6A datasheet (PDF)
Independent supplier — new & surplus stockAuthenticity-screened · ESD-safe packingListing updated Jul 2026

Specifications

STM8S105K4U6A specifications
ParameterValue
SeriesSTM8S
MountingSurface Mount
Oscillator typeInternal
Program memory typeFLASH
Voltage - supply (Vcc (Vdd))2.95V ~ 5.5V
Operating temperature-40°C ~ 85°C (TA)
Speed16MHz
PackageTray
RAM size2K x 8
Core size8-Bit
EEPROM size1K x 8
PeripheralsBrown-out Detect/Reset, POR, PWM, WDT
ConnectivityI²C, IrDA, LINbus, SPI, UART/USART
Number of i (O)25
Core processorSTM8
Case32-UFQFN Exposed Pad
Data convertersA/D 7x10b
Program memory size16KB (16K x 8)

Product details

The supply range spans 2.95 V to 5.5 V, so it can sit on either a 3.3 V or a 5 V rail without a level shifter on the MCU side. On-chip peripherals include a 7-channel 10-bit ADC, I²C, SPI, UART/USART, LIN, and IrDA, plus a full set of timers and PWM.

The 2 KB RAM handles a few buffered UART packets and local variables without overflow. The 1 KB EEPROM, rated for 100k write cycles per the STM8S family spec, stores calibration constants and configuration parameters that survive power loss. If your firmware needs OTA staging or a large lookup table, the 16 KB Flash budget will be tight; plan the memory map early.

Supply voltage and I/O tolerance

At 5 V the I/O pins swing rail-to-rail, so you can drive a 5 V relay coil driver or a logic-level MOSFET gate directly. At 3.3 V the 16 MHz core runs without wait states — no speed penalty for dropping to the lower rail.

Package and thermal — 32-UFQFPN exposed pad

Without that, the 16 MHz core at 5 V and full I/O load can push the die temperature past 85°C in a still-air enclosure.

Frequently asked questions

What is the difference between STM8S105K4U6A and STM8S105K6T6C?

The STM8S105K6T6C is a higher-density sibling in the same family: it has 32 KB Flash and 2 KB RAM versus the K4's 16 KB Flash and 2 KB RAM. The K6 also comes in a 32-LQFP (7x7 mm) package instead of the K4's 32-UFQFPN (5x5 mm). Both run at 16 MHz and share the same peripheral set and supply range. If your firmware fits in 16 KB and you need the smaller footprint, the K4 is the right choice; if you need the extra Flash for a larger application, step up to the K6.

Does STM8S105K4U6A have an internal oscillator or require external?

It has an internal oscillator. No external crystal is required for basic operation. If your application needs a precise clock for CAN, LIN, or timekeeping, you can feed an external clock signal through the appropriate pin.

Can I program STM8S105K4U6A using an ST-Link debugger?

Yes, the STM8S family uses the SWIM (Single Wire Interface Module) protocol, which is supported by the ST-Link debugger. Connect SWIM, ground, and supply — the ST-Link will handle programming and debugging.