DDS-dat
DDS, or Direct Digital Synthesis, is a specific method used by modern signal generators to create these waveforms digitally.
How DDS Works
Unlike old-school analog generators that use physical capacitors and inductors to oscillate, DDS builds a wave "by the numbers."
- Phase Accumulator: Think of this as a digital wheel spinning at a set speed. The faster it spins, the higher the frequency.
- Lookup Table (ROM): This stores the digital "coordinates" of a perfect wave (e.g., a Sine wave). The accumulator tells the table which coordinate to look at next.
- DAC (Digital-to-Analog Converter): Converts those digital coordinates into an actual voltage level.
- Low-Pass Filter: Smooths out the "staircase" steps from the digital conversion into a clean, smooth wave.
Chips
AD9857
- DDS-dat - DAC-dat - clock-multiplier-dat - filter-digital-dat - DSP-dat - AD9857-dat - analog-device-dat
https://www.analog.com/media/en/technical-documentation/data-sheets/ad9857.pdf
The AD9857 integrates a high speed direct digital synthesizer (DDS), a high performance, high speed, 14-bit digital-to-analog converter (DAC), clock multiplier circuitry, digital filters, and other DSP functions onto a single chip, to form a complete quadrature digital upconverter device. The AD9857 is intended to function as a universal I/Q modulator and agile upconverter, single-tone DDS, or interpolating DAC for communications applications, where cost, size, power dissipation, and dynamic performance are critical attributes.
The AD9857 offers enhanced performance over the industrystandard AD9856, as well as providing additional features.
The AD9857 is available in a space-saving, surface-mount package and is specified to operate over the extended industrial temperature range of −40°C to +85°C.
AD9833 — Programmable Waveform Generator
- Module: AD9833 Programmable Waveform Generator Module (Sine, Triangle, Square)
- Link: AD-interface-dat
Short description: The AD9833 from Analog Devices is a low-power (≈12.65 mW) programmable DDS waveform generator that produces sine, triangle and square waves. It operates from 2.3 V to 5.5 V and is controlled over a simple 3-wire SPI-compatible interface for easy microcontroller integration.
Key specifications
| Parameter | Value |
|---|---|
| Supply voltage | 2.3 V – 5.5 V |
| Typical power | ≈12.65 mW |
| Waveforms | Sine, Triangle, Square (square via MSB toggling) |
| Maximum output frequency | Up to 12.5 MHz (depending on clock) |
| Interface | 3-wire SPI (compatible with Arduino, DSP) |
| Frequency resolution | 28-bit frequency register (≈0.1 Hz resolution with 25 MHz clock) |
| Output | Unbuffered; typical up to ~0.65 Vpp (sine/triangle) depending on supply and load |
| Special modes | Power-down (SLEEP) mode |
Notes
- The AD9833 provides a frequency tuning word (28-bit) that gives very fine frequency resolution when driven by a stable reference clock (example: ~0.1 Hz resolution with a 25 MHz clock).
- The raw output is unbuffered; add a buffer/amplifier or filtering stage (LPF) if you need larger amplitude or lower harmonic content.
Common uses
- Low-cost frequency and waveform generation for test rigs
- Excitation signals for flow meters and sensors
- Sensing, actuation, and time-domain reflectometry (TDR)
- Impedance spectroscopy and other lab instrumentation