LTC1661 DAC

The LTC1661 from Linear Technology hosts two 10-bit DAC’s that are addressable via SPI 1. Communication is configured with the SPI clock idling low and capturing data on the rising edge of the clock. The maximum baud rate of the LTC1661 is 10MHz 2.

Timing Diagram of LTC1661 SPI communication 2

Communication with this DAC is slightly more complicated due to the 10-bit resolution associated with the device. Commanding the device to write to its internal register and Update is the primary functionality desired for this module. Knowing this, the commands 0x9 or 0xA would be applicable for continuously changing voltage on output A and B respectively 2

SPI communication Sequence for the LTC1661 2.

In our program, we must parse the data for every transmission so that a word packet sent will have the format seen in figure 2. The LTC1661 sends the command, then splits the data bits between the two bytes, followed by don’t cares to fill the word packet. In an 8-, 12-, or 16-bit DAC, less bit manipulation is required.

References

1

“Serial peripheral interface,” Wikipedia, 27-Sep-2022. [Online]. Available: https://en.wikipedia.org/wiki/Serial_Peripheral_Interface. [Accessed: 19-Oct-2022].

2(1,2,3,4)

“Ltc1661 – micropower dual 10-bit DAC in MSOP - Analog Devices.” [Online]. Available: https://www.analog.com/media/en/technical-documentation/data-sheets/1661fb.pdf. [Accessed: 17-Oct-2022].