Digital-to-Analog Converters and digital potentiometers are often used for system calibration or to dynamically control system parameters. Digipots have become a ubiquitous upgrade to variable resistors, rheostats and mechanical potentiometers. However, there are situations where a digipot is insufficient. For example, accurate motor control or sensor applications require the higher resolution capabilities of DACs. A DAC also contains an output amplifier, allowing it to drive low impedance loads and supply greater output currents.

Benefits of Non-Volatile Memory
Conventional DAC devices store configuration bits and input data in volatile memory. This data stored in the volatile memory is lost when the device loses operating power and consequently the data must be reprogrammed again from an accompanying MCU. If the DAC is used to provide a reference voltage for another device, losing the DAC output during power failure can jeopardize the functionality of the entire application. Therefore the integration of non-volatile memory, or EEPROM, can be a valuable add-on feature. The MCP4725 (datasheet) DAC is part of a new generation of the DAC devices from Microchip Technology that integrate EEPROM for configuration register data and I2C address bits. Microchip’s EEPROM technology guarantees 1,000,000 write cycles, which is a significant reliability improvement when compared to mechanical potentiometers.

In the event of power down or power loss the configuration data is automatically reloaded from the EEPROM to the DAC register when the DAC is next powered up. There is no need to wait for programming data from a microcontroller. This saves microcontroller resources and thus power. Standalone systems are even enabled; in applications where the output does not need to change connections to the microcontroller can be entirely severed. A specialized communications protocol allows the configuration data to be stored either to the EEPROM or to the DAC
register separately, or to both simultaneously.

DAC Applications
In many applications the DAC is used as a supporting device for the functionality of another device in the system. The low cost 12-bit MCP4725 DAC controls the trip voltage of the comparator giving the sensor intelligence.

Conlusion
Whether a DAC is needed for set-point or offset trimming, dynamic calibration or closed loop control, integrated EEPROM is a low-cost feature that can provide much flexibility and benefit to the designer. Reduction in microcontroller overhead, power consumption, and cost can be achieved by using non-volatile DACs, such as the MCP4725 DAC.

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