Microchip Technology AT97SC3205-U3A15-20

Overview

AT97SC3205-U3A15-20 from Microchip (acquired 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 SPI interface up to 45MHz - deployed in PC motherboard firmware stacks for secure boot and key attestation.

For engineers reviewing the AT97SC3205-U3A15-20 datasheet, AT97SC3205-U3A15-20 pinout, AT97SC3205-U3A15-20 application, or AT97SC3205-U3A15-20 equivalent, this page delivers verified package mapping (32-pin QFN), SPI-TIS 1.3 interface compliance, FIPS-140-2 module certification scope, GPIO express indexing, and physical presence signaling - all critical for BIOS integration and tamper-aware system design.

Technical Context

The AT97SC3205-U3A15-20 implements the TCG TPM 1.2 specification using an on-die AVR 8-bit RISC CPU with dedicated crypto acceleration hardware for RSA key generation, HMAC, AES encryption, and SHA hashing. Its internal EEPROM stores RSA keys and supports dynamic key cache management without host intervention.

It communicates exclusively via SPI (TIS 1.3 compliant) with active-low signals including SPI_CS#, SPI_RST#, PIRQ#, and PP/GPIO for hardware physical presence assertion. The chip includes tamper detection via XTamper pin and enters low-power mode automatically during idle periods - no software control required.

Key Specifications

Pinout & Package

AT97SC3205-U3A15-20 uses the 32-pad QFN (32M3) package: 4.0×4.0×0.9mm body, 0.4mm pitch, exposed thermal pad tied internally to GND. Pin 1 marked by corner cut; substrate center pad must be connected to system ground for EMI and thermal performance.

Key Features

Applications

Equivalent & Alternatives

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

Compared with SLB9670 and NPCT750, the AT97SC3205-U3A15-20 uniquely combines FIPS-140-2 module certification, SPI-TIS 1.3 compatibility, and industrial temperature support in a compact QFN - making it the preferred choice for long-lifecycle embedded systems requiring validated TPM 1.2 functionality without architectural overhaul.

Availability

AT97SC3205-U3A15-20 is available at Aetrix Electronics and suitable for secure boot validation, platform integrity attestation, firmware update authentication, and remote attestation services requiring stable component supply across extended product lifecycles.

Supply support for AT97SC3205-U3A15-20 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 support for legacy Atmel security products including the AT97SC3205 series.

The AT97SC3205 belongs to Atmel's Trusted Platform Module product line, designed specifically to deliver certified, turnkey hardware security for PC client platforms and industrial embedded systems requiring TCG-compliant root-of-trust functionality.

FAQ

What is the interface protocol supported by the AT97SC3205-U3A15-20?

The AT97SC3205-U3A15-20 supports only the Serial Peripheral Interface (SPI) protocol, compliant with the TCG PC Client-Specific TPM Interface Specification (TIS) Version 1.3. It does not support LPC, I²C, or UART interfaces. The SPI interface operates up to 45MHz, though typical PC implementations use 24–33MHz for timing margin and noise immunity. All command/response transactions follow TIS-defined framing and timing requirements.

Does the AT97SC3205-U3A15-20 include FIPS-140-2 certification?

Yes, the AT97SC3205-U3A15-20 is FIPS-140-2 Level 2 certified as a complete module, covering its hardware random number generator (RNG), HMAC, AES, SHA, and RSA cryptographic engines. This certification applies to the entire device - not just individual algorithms - and was validated under the NIST Cryptographic Module Validation Program. The certification remains valid for the AT97SC3205-U3A15-20 part number as shipped by Microchip.

What is the purpose of the PP/GPIO pin on the AT97SC3205-U3A15-20?

The PP/GPIO pin on the AT97SC3205-U3A15-20 serves as the Hardware Physical Presence indicator, asserted active-high to confirm user authorization before executing sensitive TPM commands such as TPM_Clear or TPM_OwnerSetDisable. It is internally pulled down, so it must be left floating or tied to ground when unused. Its function is mandated by the TCG PC Client specification to prevent unauthorized administrative actions without physical user interaction.

Can the AT97SC3205-U3A15-20 be used in industrial temperature environments?

Yes, the AT97SC3205-U3A15-20 is rated for industrial temperature operation from −40°C to +85°C. This rating is confirmed in the official Atmel ordering information and applies to the U3A15-20 variant, which uses the 32-pin QFN (32M3) package. The device maintains full TCG TPM 1.2 functionality, SPI timing compliance, and FIPS-140-2 cryptographic operation across this full range without derating.

How much non-volatile user storage does the AT97SC3205-U3A15-20 provide?

The AT97SC3205-U3A15-20 provides 2066 bytes of NV storage space for user-defined data, allocated in the TPM's NV index space. This space is distinct from the internal EEPROM used for RSA key storage and is accessible via standard TCG commands like TPM_NV_DefineSpace and TPM_NV_Write. It supports write-once and read/write attributes per index, enabling flexible use for platform configuration hashes, sealed secrets, or policy objects.