Microchip Technology AT97SC3205T-U3A16-20

Overview

AT97SC3205T-U3A16-20 from Microchip Technology (formerly Atmel) is a TCG-compliant Trusted Platform Module (TPM) 1.2 security IC implementing hardware-based asymmetric cryptography, FIPS-140-2 certified RNG/AES/SHA/RSA engines, and 2066-byte NV user storage. It integrates an AVR® RISC microprocessor and operates at 3.3V with I²C interface up to 400kHz for secure boot and platform authentication in embedded systems.

For engineers reviewing the AT97SC3205T-U3A16-20 datasheet, AT97SC3205T-U3A16-20 pinout, AT97SC3205T-U3A16-20 application, or AT97SC3205T-U3A16-20 equivalent, key selection criteria include TPM 1.2 compliance, I²C timing constraints (SM_DAT/SM_CLK pull-up guidance), GPIO-Express-00 mapping to TPM_NV_INDEX_GPIO_00, low-power TWI_Wakeup# recovery sequence, and dual-package support (28-pin TSSOP / 32-pad QFN).

Technical Context

The AT97SC3205T-U3A16-20 implements the full TCG TPM 1.2 specification stack in silicon, including command parsing, cryptographic acceleration, and secure key management via internal EEPROM. Its AVR CPU executes firmware that enforces physical security countermeasures and manages dynamic RSA key caching without host intervention.

Communication occurs exclusively over a two-wire I²C interface (SM_DAT/SM_CLK) supporting both Standard (100kHz) and Fast Mode (400kHz), with strict timing requirements on clock duty cycle and external pull-up values (800Ω on SM_DAT, 1.5kΩ on SM_CLK confirmed for 400kHz stability). The device enters automatic low-power sleep when idle and recovers only upon dual active-low assertion of TWI_Wakeup# pins.

Key Specifications

Pinout & Package

AT97SC3205T-U3A16-20 is available in two RoHS-compliant packages: 28-pin Thin TSSOP (4.40mm × 9.70mm body, 0.65mm pitch) and 32-pad QFN (4.00mm × 4.00mm body, 0.40mm pitch). Pin functions are identical across packages; NC pins differ per variant and must be tied per datasheet guidance.

Key Features

Applications

Equivalent & Alternatives

The following parts are listed as comparable options for similar TPM security applications.

Compared with Infineon SLB9670 and Nuvoton NPCT750, the AT97SC3205T-U3A16-20 delivers verified TPM 1.2 interoperability with mature driver support, 400kHz I²C for fast measurement logging, and FIPS-140-2 certification covering all core crypto engines - making it the most robust choice for maintaining compatibility in deployed industrial and server platforms.

Availability

AT97SC3205T-U3A16-20 is available at Aetrix Electronics and suitable for server platform security, industrial control authentication, and network equipment trust anchor applications requiring stable component supply and long-term lifecycle assurance.

Supply support for AT97SC3205T-U3A16-20 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

Microchip Technology acquired Atmel in 2016 and maintains full product support, documentation, and manufacturing continuity for the AT97SC3205T series.

The AT97SC3205T-U3A16-20 belongs to Atmel's Trusted Platform Module family, designed specifically to deliver certified, single-chip TPM 1.2 functionality for embedded systems requiring hardware-rooted security without external crypto components.

FAQ

What is the primary compliance standard met by the AT97SC3205T-U3A16-20?

The AT97SC3205T-U3A16-20 fully complies with the Trusted Computing Group (TCG) Trusted Platform Module (TPM) Version 1.2 Specification. It implements all mandatory command sets, PCR architecture, and key hierarchy defined in the standard, enabling interoperable trusted computing across BIOS, OS, and firmware layers. This compliance is foundational to its role as a hardware root-of-trust in server, industrial, and network equipment.

Does the AT97SC3205T-U3A16-20 support both TSSOP and QFN packages, and how do they differ electrically?

Yes, the AT97SC3205T-U3A16-20 is offered in both 28-pin Thin TSSOP and 32-pad QFN packages. Electrically, pin functions and I/O characteristics are identical between packages - including VCC, GND, SM_DAT, SM_CLK, GPIO-Express-00, and TWI_Wakeup# behavior. Only mechanical dimensions, thermal performance, and NC pin count differ; no redesign or firmware change is needed when migrating between them.

What are the exact I²C pull-up resistor values recommended for reliable 400kHz operation of the AT97SC3205T-U3A16-20?

For stable 400kHz Fast Mode I²C operation, the AT97SC3205T-U3A16-20 datasheet specifies 800Ω on the SM_DAT line and 1.5kΩ on the SM_CLK line. These values were validated to ensure signal integrity, rise/fall time compliance, and noise immunity. Deviating significantly may cause communication failures, especially under temperature or capacitive load variations.

How does the AT97SC3205T-U3A16-20 manage RSA key storage and caching?

The AT97SC3205T-U3A16-20 uses internal EEPROM for persistent RSA key storage and implements a dynamic hardware-managed key cache. It automatically loads keys into SRAM upon TPM_LoadKey2 and evicts them via TPM_FlushSpecific without host intervention. This eliminates software overhead for memory management while maintaining isolation between keys and preventing leakage across sessions.

What is the function of the TWI_Wakeup# pins on the AT97SC3205T-U3A16-20, and how must they be driven?

The AT97SC3205T-U3A16-20 features two TWI_Wakeup# pins (TSSOP pins 7 & 22; QFN pins 19 & 24) that jointly enable recovery from low-power deep sleep. To exit sleep, both pins must be pulsed active-low simultaneously. If unused, pin 7 may float or tie to GND; pin 22 must be tied to GND or VCC - failure to assert both correctly will leave the device unresponsive after TPM_DeepSleep.