Linear Technology introduces the LTC2645, a quad-channel 12- bit/10-bit/8-bit PWM-to-voltage output digital-to-analog converter (DAC) with 10 ppm /°C reference. These parts convert PWM input signals to 12-bit accurate, stable, buffered voltage outputs in less than 8 µs, eliminating the ripple and delay typically associated with analog 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 LTC2645 is ideal for biasing, calibration, level setting, power supply adjustment, and to enable opto-isolated communications in applications such as industrial automation, 4-20 mA process control, instrumentation, test equipment and optical modules. A dual version, the LTC2644, is 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 30 Hz up to 100 kHz. 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 analog filter implementations, which require the PWM to run continuously. Each rail-to-rail DAC output is capable of sourcing or sinking 5 mA (3 V) or 10 mA (5 V), and offers a full-scale output of 2.5 V using the internal 10 ppm /°C reference or a full-scale output equal to the external reference.
The LTC2645 operates from a single 2.7 V to 5.5 V supply, and supports PWM input voltages from 1.71 V to 5.5 V. The device consumes just 4 mA from a 3 V supply, and offers a <1 µA 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. Pricing begins at $3.95 each for the LTC2645-12 in 1,000-piece quantities. The DC2197A evaluation board for the LTC2645 family is supported by the Linduino Firmware Development System, using DC2026 and is available at a local Linear Technology sales office.
Summary of Features: LTC2645
- No Latency PWM-to-Voltage Conversion
- Voltage Output Updates & Settles within 8 µs
- 100 kHz to 30 Hz PWM Input Frequency
- ±2.5 LSB Max INL; ± 1LSB Max DNL
- Guaranteed Monotonic
- Pin-Selectable Internal or External Reference
- 2.7 V to 5.5 V Supply Range
- 1.71 V to 5.5 V Input Voltage Range
- Low Power: 4 mA at 3 V, <1 µA Power- Down
- -40°C to 125°C Operating Temperature Range
- Tiny 4.9 mm × 4 mm 16-Lead MSOP
