STMicroelectronics ST72F621J4T1

Overview

ST72F621J4T1 from STMicroelectronics is an 8-bit Flash-based microcontroller optimized for low-speed USB peripheral applications, featuring 16 KB dual-voltage Flash program memory, 768 bytes RAM (with 128-byte stack), integrated USB 2.0 interface with 3 endpoints and on-chip 3.3 V regulator, 10-bit ADC with up to 8 input channels, and two 8-bit timers (ART and TBU). It operates from 4.0–5.5 V and supports industrial temperature range (0°C to +70°C) in LQFP44 package.

For engineers reviewing the ST72F621J4T1 datasheet, ST72F621J4T1 pinout, ST72F621J4T1 application, or ST72F621J4T1 equivalent, this MCU is selected for embedded USB human interface devices (HID), sensor concentrators, and industrial control nodes requiring integrated USB connectivity, analog sensing, and deterministic real-time interrupt handling with low power consumption in WAIT/HALT modes.

Technical Context

The ST72F621J4T1 implements a Harvard-architecture 8-bit ST7 core with 63 instructions, nested interrupts, and true bit manipulation. Its USB subsystem includes a dedicated Serial Interface Engine (SIE) with DMA support, suspend/resume capability, and internal transceivers-eliminating need for external PHY.

Peripheral integration centers on real-time responsiveness: the Auto-Reload Timer (ART) provides two PWM outputs and two input capture channels with external clock input; the Time Base Unit (TBU) delivers cascaded periodic interrupts; and the 10-bit ADC achieves 120 kSPS conversion rate with configurable sampling time and channel sequencing.

Key Specifications

Pinout & Package

LQFP44 package (10 × 10 mm, 0.8 mm pitch), RoHS-compliant, with exposed thermal pad. Pin 39 is reserved and must remain unconnected.

Key Features

Applications

Equivalent & Alternatives

The following parts are listed as comparable options for similar 8-bit USB microcontroller applications.

Compared with ST72F621J4T1, the ST72F622L2T6 offers identical USB/analog/timer architecture at reduced memory cost, while the STM8S105K4T6 trades integrated USB simplicity for full-speed capability and modern core features - making ST72F621J4T1 optimal for cost-sensitive, low-speed USB peripheral designs where minimal external components are critical.

Availability

ST72F621J4T1 is available at Aetrix Electronics and suitable for industrial sensor nodes, USB human interface devices, and embedded firmware updater tools requiring stable component supply and long-term manufacturing continuity.

Supply support for ST72F621J4T1 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, sensors, and automotive electronics since 1987.

The ST7 family was engineered specifically for cost-sensitive, USB-enabled embedded control applications - emphasizing integration of USB SIE, analog peripherals, and low-power operation in 8-bit architectures for industrial and consumer peripherals.

FAQ

Does ST72F621J4T1 support USB suspend/resume functionality?

Yes. The device implements full USB 2.0 low-speed suspend and resume operations via its integrated Serial Interface Engine (SIE). During suspend, current drops to <100 µA; resume is triggered by bus activity or external interrupt, with wake-up time under 4 µs. The USBVCC regulator remains active during suspend to maintain transceiver bias.

What is the maximum ADC sampling rate and how is it achieved?

The 10-bit ADC achieves up to 120 kSPS by configuring the sampling time to minimum (1 ADC clock cycle) and using internal RC oscillator at 16 MHz. Conversion time is fixed at 13 ADC clock cycles; actual rate depends on selected clock source and prescaler. External crystal (6/12 MHz) yields ~60–90 kSPS in typical configurations.

Can ST72F621J4T1 operate from a 3.3 V supply?

No. The ST72F621J4T1 requires 4.0–5.5 V on VDD for guaranteed operation. While ROM variants (e.g., ST72621J4) support 3.0–5.5 V, the F-series Flash version mandates minimum 4.0 V to ensure reliable Flash programming and erase margins. USBVCC output remains 3.3 V regardless of VDD.

Is external crystal mandatory for USB operation?

No. The internal RC oscillator can generate the 48 MHz USB clock via PLL when driven by a 6 MHz external crystal or clock source. However, USB specification requires ±0.25% clock accuracy; only 6 MHz or 12 MHz crystals meet this tolerance. Using internal RC alone does not satisfy USB timing compliance.