STMicroelectronics ST72F621J4B1

Overview

ST72F621J4B1 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 hardware timers (ART and TBU). It operates from 4.0–5.5 V and supports industrial temperature range (0°C to +70°C) in PDIP42 package.

For engineers reviewing the ST72F621J4B1 datasheet, ST72F621J4B1 pinout, ST72F621J4B1 application, or ST72F621J4B1 equivalent, key selection criteria include USB endpoint count, Flash programmability in-system, analog input channel count, high-sink I/O capability (8 mA @ 0.4 V), and support for WAIT/HALT power-saving modes in embedded USB peripherals.

Technical Context

This MCU implements the ST7 8-bit CISC core with 63 instructions, nested interrupts, true bit manipulation, and 8×8 unsigned multiply. Its USB interface integrates a Serial Interface Engine (SIE), DMA controller, suspend/resume logic, and internal transceivers compliant with USB 2.0 low-speed (1.5 Mbps) specification.

The analog subsystem includes a 10-bit successive-approximation ADC with configurable sampling time and conversion trigger sources (timer, software, external event). The ART timer provides PWM generation, input capture, and external clock input, while the TBU delivers periodic interrupt timing cascaded with ART.

Key Specifications

Pinout & Package

ST72F621J4B1 is supplied in a 42-pin plastic dual in-line package (PDIP42) with 0.6-inch body width and 0.1-inch lead pitch. Pin functions are validated per STMicroelectronics Doc ID 6996 Rev 5, Section 2.

Key Features

Applications

Equivalent & Alternatives

The following parts are listed as comparable options for similar USB peripheral microcontroller applications.

Compared with ST72F621J4B1, ST72F622L2 trades Flash flexibility for lower unit cost and ROM reliability, while STM8S105K4T6C offers modern architecture and speed at the expense of USB integration and DIP42 compatibility.

Availability

ST72F621J4B1 is available at Aetrix Electronics and suitable for USB HID peripherals, industrial sensor nodes, USB-to-serial bridges, and embedded configuration tools requiring stable component supply across long-lifecycle designs.

Supply support for ST72F621J4B1 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 ICs, sensors, and automotive-grade components since 1987.

The ST7 family was engineered specifically for cost-sensitive, USB-connected embedded peripherals requiring robust Flash programmability, analog integration, and industrial temperature resilience - targeting point-of-sale terminals, lab instruments, and industrial I/O modules.

FAQ

What USB speed and compliance level does ST72F621J4B1 support?

ST72F621J4B1 supports only USB 2.0 low-speed (1.5 Mbps) operation and is fully compliant with the USB 2.0 specification for low-speed devices. It includes an integrated Serial Interface Engine (SIE), on-chip 3.3 V regulator, and differential transceivers - eliminating the need for external PHY components. High-speed or full-speed USB is not supported.

Can ST72F621J4B1 operate from a 3.3 V supply?

No - ST72F621J4B1 requires a 4.0–5.5 V digital supply (VDD). Its USBVCC pin outputs a regulated 3.3 V for powering external USB pull-up resistors or analog sensors, but the core logic and I/O operate strictly at 5 V nominal. Using 3.3 V on VDD will prevent proper operation and may damage the device.

How many analog input channels does the 10-bit ADC support?

The integrated 10-bit successive-approximation ADC supports up to 8 single-ended analog inputs (AIN0 through AIN7), mapped to PA0–PA7. All channels share one sample-and-hold circuit; conversion is sequential and software- or timer-triggered. Input voltage range is 0 V to VDDA (typically 5 V), with VSSA as analog ground reference.

Is ST72F621J4B1 still in active production?

ST72F621J4B1 is marked as "Obsolete Product(s)" in STMicroelectronics' official documentation (Doc ID 6996 Rev 5, page 1). While Aetrix Electronics maintains legacy inventory and supports design-in for existing programs, new designs should consider migration paths such as the STM8S or STM32G0 series with USB support and active long-term availability.