Module is a dual 12-bit PWM-to-voltage output DAC with high accuracy. The board is based on the LTC2644 chip. The LTC2644 measures the period and pulse width of the PWM input signals and updates the voltage output DACs after each corresponding PWM input rising edge. The DAC outputs update and settle to 12-bit accuracy within 8μs typically and are capable of sourcing and sinking up to 5mA (3V) or 10mA (5V), eliminating voltage ripple and replacing slow analog filters and buffer amplifiers. The circuit has a full-scale output of 2.5V using the 10ppm/°C internal reference. It can operate with an external reference, which sets the full-scale output equal to the external reference voltage. Each DAC enters a pin-selectable idle state when the PWM input is held unchanged for more than 60ms. The project operates from a single 2.7V to 5.5V supply and supports PWM input voltages from 1.71V to 5.5V. The PWM frequency can be any frequency between 30Hz and 6. 25kHz. The input level can be between 1.71V and 5.5V, set by a separate IOVCC pin. This project solves many problems associated with filtering a PWM signal to produce an analog voltage, producing a fast-settling, accurate analog voltage in response to a digital PWM input.
Module is a dual 12-bit PWM-to-voltage output DAC with high accuracy. The board is based on the LTC2644 chip. The LTC2644 measures the period and pulse width of the PWM input signals and updates the voltage output DACs after each corresponding PWM input rising edge. The DAC outputs update and settle to 12-bit accuracy within 8μs typically and are capable of sourcing and sinking up to 5mA (3V) or 10mA (5V), eliminating voltage ripple and replacing slow analog filters and buffer amplifiers. The circuit has a full-scale output of 2.5V using the 10ppm/°C internal reference. It can operate with an external reference, which sets the full-scale output equal to the external reference voltage. Each DAC enters a pin-selectable idle state when the PWM input is held unchanged for more than 60ms. The project operates from a single 2.7V to 5.5V supply and supports PWM input voltages from 1.71V to 5.5V. The PWM frequency can be any frequency between 30Hz and 6. 25kHz. The input level can be between 1.71V and 5.5V, set by a separate IOVCC pin. This project solves many problems associated with filtering a PWM signal to produce an analog voltage, producing a fast-settling, accurate analog voltage in response to a digital PWM input.
For standalone operation. Connect a 2.7V to 5.5V supply to the VCC and a GND of CN1 Pin 1 and Pin 4. Connect the IOVCC(IOV) to VCC using Jumper J2 such that the input logic level matches the VCC supply. If a different logic level is required, remove the IOVCC(IOV) jumper and connect the middle pin2 of J2 to a supply equal to the PWM signals’ logic level to the IOVCC(IOV) and GND. There is no sequencing requirement between VCC and IOVCC. Any convenient PWM source can be used to convert the PWM signal into a voltage output.
REF: Reference Output/Input. When the REFSEL jumper is set to INT, the LTC2645’s internal reference can be measured at this point. Nominal impedance is 500Ω. If it is used to drive external circuits it must be buffered appropriately. When REFSEL is set to EXT using Jumper J3, an external reference between 1V and VCC may be connected to this point
LTC2644-L12: Supports Frequency up to 6.25Khz, for higher frequency select below chips.
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