The DS3645 is a secure supervisor with 4096 bytes of SRAM for applications requiring the secure storage of sensitive data and the physical tamper-sensing response functions required in cryptographic processors and data security equipment.
One of the DS3645's primary features is the on-chip encryption key memory, consisting of 32 128-byte banks incorporating a high-speed, direct-clearing function. The 4KB key memory is constantly complemented in the background to prevent memory imprinting. In the event of a qualified tamper event, the key memory is rapidly cleared and a negative bias is applied to clear SRAM external to the DS3645.
The device includes a real-time clock (RTC) seconds counter, watchdog timer, CPU supervisor, nonvolatile (NV) SRAM controller, and on-chip temperature sensor. In the event of a primary power failure, an external battery source is automatically switched in to keep the key memory, RTC, and tamper-detection circuitry active. The DS3645 provides low-leakage tamper-detection inputs for interface to external sensors, interlocks, and antitamper meshes. The DS3645 also invokes a tamper event if the backup battery drops below a specified threshold or absolute temperature, if the temperature rate-of-change exceeds programmed limits, or if the crystal oscillator frequency falls outside a specified window. The tamper event is latched and timestamped for future debugging purposes.
Access to the RTC, tamper monitoring, key memory, and device configuration is conducted through an I²C-compatible interface. The DS3645 is assembled in a Pb-free CSBGA package, which enhances key security because the leads are not exposed to the outer edges of the package.
Key Features
Applications/Uses
4096-Byte Nonimprinting Key Memory with High-Speed Erase
Optional External SRAM Clear Upon Qualified Tamper Event
64-Byte General-Purpose RAM (Not Cleared)
32-Bit RTC Seconds Counter
Watchdog Timer
CPU Supervisor
Four General-Purpose Tamper-Detect Comparators
Four Window Comparators with On-Chip Reference Voltages
Two Tamper-Detect Logic Inputs
On-Chip, Programmable Temperature Sensing with Proprietary Rate-of-Change Detector
On-Chip Random-Number Generator (RNG)
Latching and Timestamping of Tamper Events
Crystal Oscillator Tamper Monitoring
Low-Power Consumption
Wide Temperature Range: -55°C to +95°C
CSBGA Package (7mm x 7mm x 0.8mm) with No Horizontally Exposed Leads
