AT91SAM7S128D-AU - 55MHz ARM7TDMI MCU, 128KB Flash, USB | Microchip
MPN: AT91SAM7S128D-AU ✓ Active| Qty | Unit Price | Extended |
|---|---|---|
| 1 | $7.93 | $7.93 |
| 10 | $7.14 | $71.40 |
| 100 | $6.35 | $635.00 |
| 500 | $5.71 | $2,855.00 |
| 1,000 | $5.08 | $5,080.00 |
AT91SAM7S128D-AU Overview
A microcontroller (MCU) is a single-chip computer that integrates a CPU core, memory (Flash for program storage, SRAM for runtime data), and a rich set of peripherals (timers, communication interfaces, ADCs, I/O). The AT91SAM7S128D-AU sits within the broader hierarchy: ARM7TDMI core -> ARM7 family -> 32-bit RISC microcontroller -> embedded MCU -> semiconductor IC. Its integrated USB 2.0 Full-Speed Device port differentiates it from competitors by eliminating the need for an external USB transceiver, reducing BOM cost and PCB area in peripheral designs.
Key features include a 55 MHz ARM7TDMI core with Thumb instruction set support, 128 KB on-chip Flash, 32 KB SRAM, USB 2.0 Full-Speed Device port, up to 32 peripheral DMA channels, a 10-bit ADC, two USARTs, one UART, two TWI (I2C-compatible) interfaces, an SPI, two 3-channel 16-bit timers, an RTT, a watchdog timer, and a real-time clock. The device operates from 3.0 V to 3.6 V supply and includes an embedded voltage regulator for core logic.
Architecturally, the SAM7S series uses a multi-layer AHB/APB bus matrix that allows simultaneous access to peripherals by the CPU and the peripheral DMA controller, eliminating data-transfer bottlenecks typical of single-bus MCUs. The integrated 3.3V LDO regulator and power-on-reset block reduce external component count to a minimum, while the Embedded Flash Controller (EFC) provides Flash read and write access with wear-leveling support.
Typical applications include USB peripherals such as HID devices, USB-to-serial adapters, USB barcode scanners, USB keyboards and mice; consumer electronics with embedded control; industrial control nodes; and migration paths for legacy 8-bit designs that require more performance. The aggressive price point and high integration make it well suited to cost-sensitive, high-volume consumer markets.
When designing with the AT91SAM7S128D-AU, engineers should ensure the 64-LQFP thermal pad is properly soldered for thermal and electrical performance, and use the integrated voltage regulator's recommended 4.7 µF decoupling capacitors. For USB applications, the D+ and D+ pull-up resistor network must follow the USB 2.0 specification for proper enumeration.
This page synthesizes distributor pricing, drop-in same-package alternatives, and practical design notes not found in the manufacturer datasheet alone.
Drop-in alternatives for AT91SAM7S128D-AU — same package, pin-to-pin compatible. Different-package parts requiring PCB rework are excluded.
Quick Comparison Tool — Select alternative parts for side-by-side comparison:
AT91SAM7S256D-AU
✅ Drop-In📋 Reference alternative (not in catalog)
AT91SAM7S512D-AU
✅ Drop-In📋 Reference alternative (not in catalog)
AT91SAM7XC128-AU
✅ Drop-In📋 Reference alternative (not in catalog)
AT91SAM7S128-AU
✅ Drop-In ⚠️ Specs Unverified📋 Reference alternative (not in catalog)
LPC2148FBD64
✅ Drop-In📋 Reference alternative (not in catalog)
STR710FZ2H6
✅ Drop-In📋 Reference alternative (not in catalog)
AT91SAM7S128D-AU Maximum Ratings & Electrical Characteristics
| Core | ARM7TDMI |
| Core Architecture | ARM7 |
| Maximum CPU Clock | 55 MHz |
| Program Memory Type | Flash |
| Program Memory Size | 128 KB (128K x 8) |
| SRAM | 32 KB |
| Operating Voltage Range | 3.0 V to 3.6 V |
| Operating Temperature Range | -40 °C to +85 °C |
| USB Interface | USB 2.0 Full-Speed Device |
| ADC | 10-bit |
| Number of I/Os | 32 |
| DMA Channels | 11 (peripheral) |
| Package | 64-LQFP (10x10 mm) |
| Mounting Type | Surface Mount |
| RoHS Status | Compliant |
AT91SAM7S128D-AU Pin Configuration
| Pin 1 | PB0 — GPIO / TIOA0 / NPCS0 |
| Pin 2 | PB1 — GPIO / TIOA1 / NPCS1 |
| Pin 3 | PB2 — GPIO / TIOA2 / NPCS2 |
| Pin 4 | PB3 — GPIO / TIOA3 / NPCS3 |
| Pin 5 | PB4 — GPIO / TCLK0 |
| Pin 6 | PB5 — GPIO / TCLK1 |
| Pin 7 | PB6 — GPIO / TCLK2 |
| Pin 8 | PB7 — GPIO |
| Pin 9 | VDDIN — Voltage regulator input |
| Pin 10 | VDDOUT — Voltage regulator output (1.8 V) |
| Pin 11 | VDP — USB D+ (USB DP) |
| Pin 12 | VDM — USB D- (USB DM) |
| Pin 13 | VBG — USB bandgap reference |
| Pin 14 | GND — Ground |
| Pin 15 | XIN — Crystal oscillator input |
| Pin 16 | XOUT — Crystal oscillator output |
| Pin 17 | NRST — Reset (active low) |
| Pin 18 | JTAGSEL — JTAG selection |
| Pin 19 | TMS — JTAG TMS |
| Pin 20 | TCK — JTAG TCK |
| Pin 21 | TDO — JTAG TDO |
| Pin 22 | TDI — JTAG TDI |
| Pin 23 | PA0 — GPIO / PWM0 / A0 |
| Pin 24 | PA1 — GPIO / PWM1 / A1 |
| Pin 25 | PA2 — GPIO / PWM2 / A2 |
| Pin 26 | PA3 — GPIO / PWM3 / A3 |
| Pin 27 | PA4 — GPIO / TIOB0 / A4 |
| Pin 28 | PA5 — GPIO / TIOB1 / A5 |
| Pin 29 | PA6 — GPIO / TIOB2 / A6 |
| Pin 30 | PA7 — GPIO / TIOB3 / A7 |
| Pin 31 | PA8 — GPIO / FIQ / A8 |
| Pin 32 | PA9 — GPIO / IRQ0 / A9 |
| Pin 33 | PA10 — GPIO / IRQ1 / A10 |
| Pin 34 | PA11 — GPIO / SHDLC / A11 |
| Pin 35 | PA12 — GPIO / A12 |
| Pin 36 | PA13 — GPIO / A13 |
| Pin 37 | PA14 — GPIO / A14 |
| Pin 38 | PA15 — GPIO / A15 |
| Pin 39 | PA16 — GPIO / SPCK / A16 |
| Pin 40 | PA17 — GPIO / MISO / A17 |
| Pin 41 | PA18 — GPIO / MOSI / A18 |
| Pin 42 | PA19 — GPIO / NPCS0 / A19 |
| Pin 43 | PA20 — GPIO / NPCS1 / A20 |
| Pin 44 | PA21 — GPIO / NPCS2 / A21 |
| Pin 45 | PA22 — GPIO / NPCS3 / A22 |
| Pin 46 | PA23 — GPIO / PWM0 / A23 |
| Pin 47 | PA24 — GPIO / PWM1 / A24 |
| Pin 48 | PA25 — GPIO / PWM2 / A25 |
| Pin 49 | PA26 — GPIO / PWM3 / A26 |
| Pin 50 | PA27 — GPIO / PWM4 / A27 |
| Pin 51 | PA28 — GPIO / PWM5 / A28 |
| Pin 52 | PA29 — GPIO / PWM6 / A29 |
| Pin 53 | PA30 — GPIO / A30 |
| Pin 54 | PA31 — GPIO / A31 |
| Pin 55 | GND — Ground |
| Pin 56 | VDD — 3.3V supply |
| Pin 57 | GND — Ground |
| Pin 58 | ADVREF — ADC reference voltage |
| Pin 59 | AD0 — Analog input 0 |
| Pin 60 | AD1 — Analog input 1 |
| Pin 61 | AD2 — Analog input 2 |
| Pin 62 | AD3 — Analog input 3 |
| Pin 63 | GND — Ground |
| Pin 64 | GND — Ground (thermal pad) |
Typical Applications
AT91SAM7S128D-AU is suitable for 6 applications: USB Human Interface Device (HID), USB to Serial / CDC Bridge Adapter, USB Barcode Scanner / Data Acquisition Device, Industrial Control / Sensor Node, Consumer Electronics with Embedded Control, Legacy 8-bit Migration Path / Educational Platform.
USB Human Interface Device (HID)
The AT91SAM7S128D-AU's integrated USB 2.0 Full-Speed Device port with 8 endpoints and on-chip transceiver makes it a strong fit for USB HID peripherals such as keyboards, mice, game controllers, and custom input devices. The 55 MHz ARM7TDMI core executes USB stack and HID report processing well within budget, while the 128 KB Flash comfortably holds HID class drivers plus application code. The 32 KB SRAM provides sufficient buffer space for HID report queuing. Designers should follow USB 2.0 specification pull-up requirements (1.5 kΩ on D+ for FS device) and use the on-chip pull-up resistor option.
Recommended
USB to Serial / CDC Bridge Adapter
The AT91SAM7S128D-AU is well-suited to USB-to-UART bridge dongles using the USB Communication Device Class (CDC). Its two on-chip USARTs map directly to the CDC data interface, and the 128 KB Flash accommodates USB-CDC stack plus optional vendor-specific control commands. Operating at 55 MHz provides ample headroom for UART baud rates up to 921600 bps without CPU bottleneck. Compared to dedicated bridge ICs (FT232R, CP2102), the SAM7S128D-AU allows firmware customization for protocol translation, GPIO control, or vendor-specific extensions in the same part.
Recommended
USB Barcode Scanner / Data Acquisition Device
With its USB 2.0 Full-Speed Device port, 32 KB SRAM for scan buffering, and 128 KB Flash for firmware including image decoding or protocol stacks, the AT91SAM7S128D-AU fits handheld barcode scanner designs and small data-acquisition peripherals. The two TWI (I2C) interfaces support sensor connections (image sensors, accelerometers), and the 10-bit ADC can read analog sensor outputs directly. The peripheral DMA controller offloads bulk data movement from the CPU, improving throughput for continuous-scan applications.
Recommended
Industrial Control / Sensor Node
The AT91SAM7S128D-AU's industrial temperature range (-40 °C to +85 °C), 3.0-3.6 V supply tolerance, and rich peripheral set (USART, SPI, TWI, ADC, timers) make it suitable for industrial sensor nodes and PLC-style control blocks. Its ARM7TDMI core delivers deterministic performance for real-time control loops, and the 32 KB SRAM supports small RTOS kernels (FreeRTOS, Micrium) for multi-task sensor fusion. The on-chip 1.8 V regulator simplifies power-tree design in 24V-to-3.3V industrial bus systems with appropriate front-end conversion.
Recommended
Consumer Electronics with Embedded Control
The AT91SAM7S128D-AU's high level of integration - USB, ADC, timers, multiple serial interfaces - combined with its aggressive price point makes it ideal for cost-sensitive consumer electronics such as toys, appliances, fitness wearables, and remote controls. The 128 KB Flash holds application firmware plus optional bootloader for firmware update via USB, and the 32 KB SRAM supports modest UI state and buffering. Compared to 8-bit PIC or AVR MCUs, the ARM7TDMI delivers significant performance headroom at a comparable price for cost-conscious consumer designs.
Recommended
Legacy 8-bit Migration Path / Educational Platform
The AT91SAM7S128D-AU is explicitly positioned as an ideal migration path from 8-bit AVR and PIC microcontrollers to 32-bit ARM performance, per the Atmel/Microchip datasheet. Its peripheral compatibility (USART, SPI, TWI similar to AVR nomenclature) and full Atmel Studio / Microchip Studio IDE support make it an excellent teaching platform for engineers moving from 8-bit to 32-bit. The 64-LQFP package is hand-solderable, breadboard-friendly with adapter boards, and well documented in application notes for university labs and hobbyist makers.
Recommended
Recommended Products Summary
Engineering reference data for AT91SAM7S128D-AU — comparison, design guidance, and compliance information.
Selection Guide
Comparison with Alternatives
| Parameter | This Product | AT91SAM7S256D-AU | AT91SAM7S512D-AU | AT91SAM7XC128-AU | AT91SAM7S128-AU | LPC2148FBD64 | STR710FZ2H6 |
|---|---|---|---|---|---|---|---|
| Package | 64-LQFP (10x10 mm) | 64-LQFP (10x10 mm) - same | 64-LQFP (10x10 mm) - same | 64-LQFP (10x10 mm) - same | 64-LQFP (10x10 mm) - same | 64-LQFP - same | 64-LQFP - same |
| Brand | Microchip Technology | Microchip Technology | Microchip Technology | Microchip Technology | Microchip Technology | NXP Semiconductors | STMicroelectronics |
| Flash Memory | 128 KB | 256 KB | 512 KB | 128 KB | 128 KB | 512 KB | 256 KB |
| SRAM | 32 KB | 64 KB | 128 KB | 32 KB | 32 KB | 32 KB | 16 KB |
| Maximum CPU Clock | 55 MHz | 55 MHz | 55 MHz | 55 MHz | 55 MHz | 60 MHz | 36 MHz |
| USB Interface | USB 2.0 FS Device | USB 2.0 FS Device | USB 2.0 FS Device | USB 2.0 FS Device | USB 2.0 FS Device | USB 2.0 FS Device | USB 2.0 FS Device |
| Operating Voltage | 3.0 - 3.6 V | 3.0 - 3.6 V | 3.0 - 3.6 V | 3.0 - 3.6 V | 3.0 - 3.6 V | 3.0 - 3.6 V | 3.0 - 3.6 V |
| Hardware Crypto Engines | No | No | No | Yes (AES, DES, SHA, TRNG) | No | No | No |
| Core | ARM7TDMI | ARM7TDMI | ARM7TDMI | ARM7TDMI | ARM7TDMI | ARM7TDMI | ARM7TDMI |
Key Differentiators
- Integrated USB 2.0 Full-Speed Device with on-chip transceiver (vs ATMEGA164A-AU)
- Higher CPU performance at competitive price (vs PIC18F25Q43-I/STX)
- Upward memory migration path in same footprint (vs AT91SAM7S128D-AU vs AT91SAM7S256D-AU)
- Optional hardware cryptographic engines on same pinout (vs AT91SAM7XC128-AU)
Design Notes
The AT91SAM7S128D-AU requires a 4.7 µF low-ESR ceramic capacitor on VDDOUT (pin 10) to stabilize the internal 1.8 V LDO regulator that supplies the core logic. Place this capacitor as close as possible to the pin with the shortest possible trace to GND. VDDIN (pin 9) is the regulator input and must be tied to the 3.3 V supply rail. Bulk decoupling of 100 nF should be placed adjacent to each VDD/GND pair, with a 10 µF bulk capacitor on the main 3.3 V rail.
Solder the exposed thermal pad (pin 64 / GND on the LQFP) to a ground copper pour with multiple thermal vias to the inner ground plane. This is required both for electrical performance (low-impedance ground return) and for thermal dissipation. The 64-LQFP has 0.5 mm pitch which requires careful PCB manufacturing - use ENIG surface finish and avoid HASL for reliable fine-pitch assembly.
USB D+ and D- traces (pins 11/12) should be routed as a 90-ohm differential pair, length-matched within 150 mil, and kept short (< 50 mm total). The on-chip USB bandgap reference (pin 13, VBG) requires a 1 µF decoupling capacitor. The 1.5 kΩ pull-up resistor on D+ for Full-Speed enumeration should be connected to 3.3 V; alternatively, the SAM7S provides an internal pull-up that can be software-enabled to save the external component.
Do not connect any I/O pin to a voltage above 3.6 V (the absolute maximum VDD) - even momentary over-voltage during hot-plug events can damage the part. For JTAG debugging, JTAGSEL (pin 18) must be tied high during reset to enable the JTAG boundary scan, or left floating to use the ARM debug interface. When using the Embedded Flash Controller for in-application programming, respect the lock-bit security model to prevent accidental code corruption.
Compliance Information
RoHS compliant per DigiKey product page. AEC-Q100 not qualified - this is an industrial/consumer grade MCU. For automotive applications, consider AEC-Q100-qualified alternatives.
