Medical disposables can be gamma-sterilised, memory survives

May 28, 2015 // By Graham Prophet
Gamma radiation-resistant memory provides calibration and protects from unsanitary reuse in medical disposables; this memory uses only one contact to simplify implementations in small, disposable medical sensors.

Maxim Integrated says it has simplified making a calibrated consumable medical sensor while also allowing monitoring or controlling unsanitary reuse of medical disposables with the DS28E80 gamma-radiation-resistant, nonvolatile (NV) 1-Wire memory.

Gamma radiation sterilisation is typically used on single-use disposable medical sensors and consumables because the method is predictable, reliable, faster to process, and usable across a wide array of product materials and packaging types. But, gamma radiation is incompatible with traditional floating-gate memory technologies used in semiconductors because gamma’s high-ionising radiation erases the memory. The DS28E80 NV memory, however, is resistant to gamma radiation up to 75 kGy (kilo Gray). With flexible programming options, it allows OEMs to factory calibrate their sensors, tools, and accessories to their host medical instrument in the field. It can be used to monitor or even prevent unsanitary reuse of a disposable medical sensor and consumables. It operates over the company’s 1-Wire interface, so consumable manufacturers can replace multiple cumbersome cables with a single contact.

Manufacturing calibration is effected as OEMs can automatically detect and calibrate sensors and accessories to ensure quality. Usage tracking guards against incorrect attachment and warns or prevents unsanitary reuse of consumables. Embedded identification comes via the 1-Wire protocol that provides a unalterable 64-bit factory-assigned serial ID which allows for tracking and can prevent usage of unauthorised consumables. The reprogrammable 248 Bytes memory is organised as 8-Byte blocks: permanent write protection is on a flexible per-blockbasis.

“We know that gamma radiation has historically been incompatible with NV memory technologies, but for some single-use medical applications gamma radiation may be the preferred method for sterilisation,” said Nathan Sharp, Business Manager at Maxim Integrated. “So we designed an NV memory that resists the radiation, connects to a host medical device simply, and then reliably monitors or prevents reuse of the consumable. It’s all as simple as its 1-Wire interface.”

The DS28E80 is specified over the -40 to +85C temperature range: a DS28E80EVKIT