Battery-backup controller features 1-kB non-imprinting SRAM

Dallas, Texas—Dallas Semiconductor, a wholly owned subsidiary of Maxim Integrated Products, has introduced the DS3641 secure battery-backup controller that offers features for data protection in point-of-sale (POS) terminals and other applications containing sensitive data.

Integrating a real-time clock (RTC), an automatic battery switch, and a 4-wire interface in a CSBGA for added security, the DS3641 controller provides active tamper detection and rapid erasure of key memory.

Due to its high level of security, the DS3641 not only supports FIPS 140 security levels 3 and 4, but also meets the highest requirements of the Common Criteria, PCI-PED, and EMV-4.1 certification entities.

A key feature of the DS3641 is the proprietary on-chip nonvolatile SRAM it uses to store encryption keys. This memory architecture constantly complements the SRAM cells to eliminate the possibility of memory imprinting due to oxide stress. This technology prevents the passive detection of data remnants in stressed memory cells.

With this memory architecture, the entire 1kB array is immediately cleared in less than 100-ns after a tamper alarm has been generated by the DS3641. This is enabled by the memory's high-speed hardwired clearing function and on-chip energy source, which ensures active erasure.

The DS3641 secure battery-backup controller provides tamper-detection inputs to interface with and provide low-power continuous monitoring of system voltages, resistive meshes, external sensors, and digital interlocks. The RTC's crystal oscillator is also monitored and will invoke a tamper response if the frequency falls outside the set threshold. The internal digital temperature sensor integrates a programmable rate-of-change detector and protects the DS3641 internal encryption-key memory from thermal attacks.

Additionally, the DS3641 constantly monitors primary power; in the event of a primary power failure, an external battery source automatically switches on to keep the SRAM, RTC, and tamper-detection circuitry alive.

The DS3641 is specified over the -40°C to +85°C temperature range.

A datasheet for this product is available by request on the web at

Dallas Semiconductor, 1-972-371-4000,

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