# STM32L021D4P7

**STMicroelectronics** · Microcontrollers (MCU/MPU/SOC) · TSSOP-14

STM32L021D4P7 from STMicroelectronics, in a TSSOP-14. Pinout and pin descriptions extracted from the manufacturer datasheet (extract_pins, cross-checked by a second model, then checked against ST open pin data); symbol, footprint, and 3D from KiCad-official CAD.

## Pinout

| Pin | Name | Type | Function |
|---|---|---|---|
| 1 | PB9-BOOT0 | input | Boot memory selection input (BOOT0), active high, determines boot from Flash or system bootloader |
| 2 | PC14-OSC32_IN | bidirectional | 32 kHz oscillator input for RTC, supports OSC32_IN function for external crystal connection |
| 3 | PC15-OSC32_OUT | bidirectional | 32 kHz oscillator output for RTC, supports OSC32_OUT function for external crystal connection |
| 4 | NRST | bidirectional | Device reset input/output (active low) with embedded weak pull-up resistor, 5V tolerant |
| 5 | PA0-CK_IN | bidirectional | Port A bit 0, ADC channel 0, 3.3V tolerant ADC input, supports alternate functions USART2_RX, LPTIM1_IN1, TIM2_CH1, LPUART1_RX, COMP1_OUT |
| 6 | PA1 | bidirectional | Port A bit 1, ADC channel 1, 5V tolerant I/O, supports alternate functions LPTIM1_IN2, TIM2_CH2, I2C1_SMBA, USART2_RTS_DE, LPUART1_TX, COMP1_INP |
| 7 | PA4 | bidirectional | Port A bit 4, ADC channel 4, 3.3V tolerant ADC input, supports alternate functions SPI1_NSS, LPTIM1 inputs, I2C1_SCL, USART2_CK, LPUART1_TX, COMP2_OUT |
| 8 | PA7 | bidirectional | Port A bit 7, ADC channel 7, 5V tolerant I/O, supports alternate functions SPI1_MOSI, LPTIM1_OUT, USART2_CTS, TIM21_ETR, COMP2_OUT, COMP2_INP |
| 9 | VSS | power_in | Digital and analog ground (GND) |
| 10 | VDD | power_in | Digital and analog power supply, 1.65V to 3.6V, internally connected to VDDA on TSSOP14 variant |
| 11 | PA9 | bidirectional | Port A bit 9, 5V tolerant FM+ capable I/O with 20mA output drive, supports MCO, I2C1_SCL, LPTIM1_OUT, USART2_TX, TIM21_CH2, COMP1_OUT |
| 12 | PA10 | bidirectional | Port A bit 10, 5V tolerant FM+ capable I/O with 20mA output drive, supports TIM21_CH1, I2C1_SDA, USART2_RX, TIM2_CH3, COMP1_OUT, RTC_REFIN |
| 13 | PA13 | bidirectional | Port A bit 13, 5V tolerant FM+ capable I/O, Serial Wire Debug Data I/O (SWDIO), supports alternate functions LPTIM1_ETR, I2C1_SDA, SPI1_SCK, LPUART1_RX, COMP1_OUT |
| 14 | PA14 | bidirectional | Port A bit 14, 5V tolerant I/O, Serial Wire Debug Clock (SWCLK), acts as SPI1_MISO when bootloader active, supports LPTIM1_OUT, I2C1_SMBA, USART2_TX, LPUART1_TX, COMP2_OUT |

## Key specifications

| Parameter | Value |
|---|---|
| Manufacturer | STMicroelectronics |
| Package | TSSOP-14 |
| Category | Embedded Processors & Controllers |
| Pins | 14 |

## CAD (KiCad official)

- Symbol: `STM32L021D4P7`
- Footprint: `Package_SO:TSSOP-14_4.4x5mm_P0.65mm`
- 3D model: TSSOP-14 (KiCad packages3D, STEP)
- 3D model files: `stm32l021d4p7-etched.step` / `stm32l021d4p7-etched.glb` carry the MPN laser-etched on the die in a toggleable `Adom.LaserEtch` group (Fusion-ready); `stm32l021d4p7.step` / `stm32l021d4p7.glb` are the bare package body.

## Provenance

Data extracted from the manufacturer datasheet, not a distributor listing:

- **Datasheet:** [STMicroelectronics datasheet](https://jlcpcb.com/api/file/downloadByFileSystemAccessId/8588922176892514304) (114 pp, sha256 `97b23667dad711b9`, retrieved 2026-10-06, tier: lcsc)
- **Extractor:** parts-factory `2.0.0` / `extract_pins 0.3`, primary `claude-haiku-4-5-20251001` (text), consensus `claude-sonnet-5-5` (agreed), guards: pin_guards 0.1: passed. Pins are checked against the footprint pad set and their cited datasheet pages before publish.
- **CAD:** KiCad official libraries (CC-BY-SA 4.0).

[Datasheet PDF](docs/stm32l021d4p7-datasheet.pdf)