ADN2850:  Nonvolatile Memory, Dual 1024-Position Digital Resistor

The ADN2850 is a dual-channel, nonvolatile memory¹, digitally controlled resistors² with 1024-step resolution, offering guaranteed maximum low resistor tolerance error of ±8%. The device performs the same electronic adjustment function as a mechanical rheostat with enhanced resolution, solid state reliability, and superior low temperature coefficient performance. The versatile programming of the ADN2850 via an SPI^®-compatible serial interface allows 16 modes of operation and adjustment including scratchpad programming, memory storing and restoring, increment/decrement, ±6 dB/step log taper adjustment, wiper setting readback, and extra EEMEM¹ for user-defined information such as memory data for other components, look-up table, or system identification information.

In the scratchpad programming mode, a specific setting can be programmed directly to the RDAC² register, which sets the resistance between Terminal W and Terminal B. This setting can be stored into the EEMEM and is restored automatically to the RDAC register during system power-on.

The EEMEM content can be restored dynamically or through external PR strobing, and a WP function protects EEMEM contents. To simplify the programming, the independent or simultaneous linear-step increment or decrement commands can be used to move the RDAC wiper up or down, one step at a time. For logarithmic ±6 dB changes in the wiper setting, the left or right bit shift command can be used to double or halve the RDAC wiper setting.

The ADN2850 patterned resistance tolerance is stored in the EEMEM. The actual full scale resistance can, therefore, be known by the host processor in readback mode. The host can execute the appropriate resistance step through a software routine that simplifies open-loop applications as well as precision calibration and tolerance matching applications.

The ADN2850 is available in the 5 mm × 5 mm 16-lead frame chip scale LFCSP and thin, 16-lead TSSOP package. The part is guaranteed to operate over the extended industrial temperature range of −40°C to +85°C.

¹ The terms nonvolatile memory and EEMEM are used interchangeably.
² The terms digital resistor and RDAC are used interchangeably.

Applications

• SONET, SDH, ATM, Gigabit Ethernet, DWDM laser diode driver, optical supervisory systems
• Mechanical rheostat replacement
• Instrumentation gain adjustment
• Programmable filters, delays, time constants
• Sensor calibration