STMicroelectronics STM32L021D4P7D

Overview

STM32L021D4P7D from STMicroelectronics is an ultra-low-power 32-bit Arm® Cortex®-M0+ microcontroller featuring 16 KB Flash, 2 KB SRAM, 512 B EEPROM with ECC, 12-bit ADC (1.14 Msps), and hardware AES-128 encryption. It operates from 1.65–3.6 V across –40 to +125 °C and delivers 0.23 µA standby current with 2 wakeup pins - deployed in battery-powered sensor nodes and smart utility meters.

For engineers reviewing the STM32L021D4P7D datasheet, STM32L021D4P7D pinout, STM32L021D4P7D application, or STM32L021D4P7D equivalent, key selection criteria include ultra-low active/standby current, integrated EEPROM retention during Stop mode, 5V-tolerant I/Os on selected pins, and support for ISO 7816/IRDA via USART - critical for secure, long-life embedded designs.

Technical Context

The device implements a dual-voltage domain architecture with dynamic voltage scaling enabling Run mode down to 76 µA/MHz and Stop mode at 0.54 µA with RTC + 2 KB RAM retention. Its clock system integrates factory-trimmed 16 MHz HSI (±1%), 32 kHz LSE for RTC calibration, and a programmable PLL for CPU frequency up to 32 MHz.

Analog subsystem includes two ultra-low-power comparators (operable down to 1.65 V) with window mode and wake-up capability, plus a 12-bit ADC supporting up to 10 channels at 1.14 Msps - all powered independently to minimize leakage in low-power states.

Key Specifications

Pinout & Package

STM32L021D4P7D uses the UFQFPN20 (3 × 3 mm, 0.5 mm pitch) package with 20 leads. This compact, leadless QFN variant supports automated optical inspection and offers superior thermal performance over TSSOP alternatives.

Key Features

Applications

Equivalent & Alternatives

The following parts are listed as comparable options for similar ultra-low-power MCU applications.

Compared with STM32L011D4P7, the STM32L021D4P7D adds essential security and data persistence via AES-128 and 512 B EEPROM; versus STM32L031F6P7, it trades package size and memory for lower power and smaller form factor - making it optimal for space-constrained, battery-critical deployments.

Availability

STM32L021D4P7D is available at Aetrix Electronics and suitable for smart metering, wearable health monitoring, industrial wireless sensing, and asset tracking requiring stable component supply across extended product lifecycles.

Supply support for STM32L021D4P7D 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, designing and manufacturing microcontrollers, power ICs, sensors, and analog devices for industrial, automotive, and consumer markets.

The STM32L0 series targets ultra-low-power embedded applications demanding multi-year battery life, secure firmware execution, and robust analog integration - optimized for metering, wearables, and IoT edge nodes.

FAQ

What is the maximum operating frequency of the STM32L021D4P7D?

The STM32L021D4P7D supports a maximum CPU clock frequency of 32 MHz, achievable via its internal 16 MHz HSI oscillator multiplied by the PLL or directly from an external high-speed clock source. The core maintains full functionality across the entire 32 kHz to 32 MHz range, with dynamic voltage scaling ensuring optimal power efficiency at each frequency point.

Does the STM32L021D4P7D support USB connectivity?

No, the STM32L021D4P7D does not include a USB peripheral. It provides USART (with ISO 7816 and IrDA support), LPUART, SPI, and I2C interfaces. For USB-based designs, engineers should consider the STM32L053 or STM32L073 series, which integrate USB 2.0 FS controllers and associated PHY circuitry.

How many I/O pins are 5V tolerant on the STM32L021D4P7D?

23 I/O pins on the STM32L021D4P7D are 5V tolerant, specifically PA0–PA7, PA10–PA15, PB0–PB1, and PC6–PC7. This tolerance applies when VDD is powered within 1.65–3.6 V and allows direct interfacing with 5V logic without external level shifters - confirmed in Section 6.3.13 of the official datasheet.

Can the internal EEPROM be used for firmware parameter storage during power loss?

Yes, the 512 B embedded EEPROM supports independent read/write operations with ECC protection and retains data across full power cycles. It is designed for frequent parameter updates (100 k write/erase cycles) and maintains integrity during brownout events - validated for use in metering calibration tables, device configuration, and security keys without external nonvolatile memory.