STMicroelectronics STM32L021D4P7TR

Overview

STM32L021D4P7TR from STMicroelectronics is an ultra-low-power 32-bit Arm® Cortex®-M0+ microcontroller featuring 16 KB Flash, 2 KB SRAM, 512 B ECC-protected EEPROM, 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 76 µA/MHz in Run mode with 5 µs wakeup from Flash-ideal for battery-powered sensor nodes and smart metering endpoints.

For engineers reviewing the STM32L021D4P7TR datasheet, STM32L021D4P7TR pinout, STM32L021D4P7TR application, or STM32L021D4P7TR equivalent, key selection criteria include ultra-low standby current (0.23 µA), 23 5V-tolerant I/Os, integrated RTC with 2 KB RAM retention in Stop mode, and support for ISO 7816/USART and low-power UART interfaces.

Technical Context

The STM32L021D4P7TR implements a single-core Arm Cortex-M0+ running at up to 32 MHz, supported by multiple clock sources including factory-trimmed 16 MHz HSI (±1%), 32 kHz LSE for RTC, and multispeed MSI (65 kHz–4.2 MHz). Its power architecture integrates programmable voltage detector (PVD), ultra-low-power brownout reset (BOR) with five thresholds, and dynamic voltage scaling for optimized active/low-power mode transitions.

Peripheral interconnect uses a centralized AHB/APB matrix enabling concurrent DMA-driven operations across ADC, SPI, I²C, USART, timers, and AES engine. The device supports five low-power modes-Run, Sleep, Low-power Run, Low-power Sleep, Stop, and Standby-with dedicated wakeup lines (16 in Stop, 2 in Standby) and sub-µA retention capability for critical data and RTC operation.

Key Specifications

Pinout & Package

STM32L021D4P7TR is housed in a 20-pin UFQFPN (3 × 3 mm, 0.5 mm pitch) package compliant with ECOPACK®2 environmental standards. This compact, lead-free, thermally enhanced package supports high-density PCB layouts and automated assembly.

Key Features

Applications

Equivalent & Alternatives

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

Compared with STM32L021D4P7TR, STM32L011D4P7TR sacrifices security and memory headroom for lower BOM cost, while STM32L031F6P7TR trades package size and standby current for scalability-making the D4P7TR optimal for space-constrained, security-aware, long-life battery applications.

Availability

STM32L021D4P7TR is available at Aetrix Electronics and suitable for smart metering, wearable health monitors, industrial wireless sensor nodes, and asset tracking beacons requiring stable component supply across multi-year production cycles.

Supply support for STM32L021D4P7TR 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, Switzerland, designing and manufacturing microcontrollers, power management ICs, MEMS sensors, and automotive-grade components since 1987.

The STM32L0 series targets ultra-low-power embedded applications, emphasizing sub-µA standby operation, integrated analog peripherals, and hardware security-specifically engineered for battery-operated IoT edge devices and energy-constrained industrial systems.

FAQ

What is the maximum operating frequency and core type of the STM32L021D4P7TR?

The STM32L021D4P7TR features an Arm Cortex-M0+ core rated for up to 32 MHz operation. It achieves 0.95 DMIPS/MHz performance with Thumb-2 instruction set support. The core is factory-calibrated for 16 MHz HSI accuracy within ±1%, and supports PLL multiplication for higher-frequency operation when required by application timing constraints.

Does the STM32L021D4P7TR support 5V-tolerant I/Os, and how many are available?

Yes, the STM32L021D4P7TR supports 23 I/O pins with 5V tolerance-confirmed in Section 3.7 of the datasheet. This allows direct interfacing with standard 5V logic peripherals (e.g., legacy sensors, displays, or level-shifter-free UART transceivers) without external protection circuitry, simplifying design and reducing BOM count in mixed-voltage systems.

How does the hardware AES-128 engine integrate with the MCU's memory and peripherals?

The AES-128 engine is accessible via dedicated APB registers and supports ECB/CBC modes with DMA-triggered operation. It reads plaintext from SRAM or Flash, writes ciphertext to SRAM, and can be synchronized with USART or SPI transfers-enabling encrypted data streaming without CPU involvement. Key storage relies on software-managed memory; no dedicated key register is present.

What are the wakeup sources and latency from Stop mode?

From Stop mode, the STM32L021D4P7TR supports wakeup via 16 configurable EXTI lines, RTC alarm, comparator events, or USART start-bit detection. Measured wakeup time is ≤5 µs when exiting to Run mode from Flash, as specified in Table 33 (Section 6.3.33). This latency includes clock stabilization and vector fetch-critical for responsive event-driven sensing.