Linear Technology has introduced the LTC2645, a quad-channel 12-bit/10-bit/8-bit PWM-to-voltage output digital-to-analogue converter (DAC) with 10ppm/°C reference. These parts convert PWM input signals to 12-bit accurate, stable, buffered voltage outputs in less than 8µs, eliminating the ripple and delay typically associated with analogue filters.
The LTC2645 provides a simple bolt-on solution to accurately set and adjust four voltages without a single line of code required. Offered in a small 16-lead MSOP package, the device is intended for biasing, calibration, level setting, power supply adjustment, and to enable opto-isolated communications in applications such as industrial automation, 4-20mA process control, instrumentation, test equipment and optical modules. A dual version, the LTC2644, is also available in a 12-lead MSOP package.
The LTC2645 measures the period and pulse width of the PWM input signals and updates the DACs after each PWM input rising edge, accepting PWM input frequencies from 30Hz up to 100kHz. An IDLSEL pin provides flexibility to set the outputs to idle at zero- or full-scale, power-down with high-impedance output, or hold the previous state indefinitely in response to an idle PWM input. This convenient mode has the advantage over analogue filter implementations, which require the PWM to run continuously. Each rail-to-rail DAC output is capable of sourcing or sinking 5mA (3V) or 10mA (5V), and offers a full-scale output of 2.5V using the internal 10ppm/°C reference or a full-scale output equal to the external reference.
The device operates from a single 2.7V to 5.5V supply, and supports PWM input voltages from 1.71V to 5.5V. The device consumes just 4mA from a 3V supply, and offers a <1µA power-down mode with high impedance outputs.
The LTC2645 is offered in 12-bit/10-bit/8-bit versions and is available today in commercial, industrial and automotive (-40°C to 125°C) temperature grades.