How to Use AD9850: Examples, Pinouts, and Specs

Introduction

The AD9850 is a high-performance Direct Digital Synthesizer (DDS) manufactured by Analog Devices, with the part ID AD9850BRSZ. It is designed to generate precise sine and square waveforms with high frequency resolution and low phase noise. The AD9850 is widely used in signal generation applications, including RF systems, audio signal processing, and function generators. Its compact design and versatile functionality make it a popular choice for both hobbyists and professionals.

Explore Projects Built with AD9850

ESP32 and ADXL343-Based Battery-Powered Accelerometer with SPI Communication

This circuit features an ESP32 microcontroller interfaced with an ADXL343 accelerometer via SPI communication, powered by a 12V battery regulated down to 5V and 8V using 7805 and 7808 voltage regulators. The ESP32 reads accelerometer data and outputs it via serial communication, with additional components including a pushbutton and a rocker switch for user input.

Open Project in Cirkit Designer

ESP32-Based Multi-Sensor Monitoring System with Battery Power

This circuit is a sensor monitoring system powered by a 7.4V battery, regulated to 5V using a 7805 voltage regulator. It uses an ESP32 microcontroller to interface with an ADXL345 accelerometer, INA219 current sensor, BMP280 pressure sensor, and an IR sensor, all connected via I2C and GPIO for data acquisition and processing.

Open Project in Cirkit Designer

ESP32-Based Voice-Activated SD Card Audio Recorder

This circuit features an ESP32 Devkit V1 microcontroller connected to a Micro SD Card Module for data storage, an Adafruit MAX9814 Electret Microphone Amplifier for audio input, and an Adafruit MAX98357A I2S Class-D Mono Amp connected to a loudspeaker for audio output. A pushbutton is interfaced with the ESP32 for user input. The circuit is likely designed for audio recording and playback with the capability to store the audio data on the SD card.

Open Project in Cirkit Designer

Arduino Pro Mini FM Radio with LCD Display and Battery Power

This circuit is a portable FM radio receiver with an integrated display and audio output. It uses an Arduino Pro Mini to control an RDA5807M FM receiver module, an ADS1115 ADC for additional analog inputs, and a PAM8403 amplifier to drive loudspeakers. The circuit also includes a rotary encoder for user input, an LCD screen for displaying information, and a boost converter for power management.

Open Project in Cirkit Designer

Common Applications

RF signal generation for communication systems
Audio signal processing and testing
Function generators and waveform synthesis
Frequency modulation and phase modulation systems
Clock generation for digital systems

Technical Specifications

The following table outlines the key technical details of the AD9850:

Parameter	Value
Supply Voltage (Vcc)	2.7V to 5.5V
Power Consumption	380 mW (typical at 5V)
Frequency Range	Up to 125 MHz
Frequency Resolution	32-bit tuning word (0.0291 Hz at 125 MHz clock)
Phase Noise	-140 dBc/Hz at 1 kHz offset
Output Waveforms	Sine wave, Square wave
DAC Resolution	10-bit
Operating Temperature Range	-40°C to +85°C
Package Type	28-lead SSOP

Pin Configuration and Descriptions

The AD9850 has 28 pins, with the following configuration:

Pin Number	Pin Name	Description
1	VCC	Positive power supply (2.7V to 5.5V)
2	GND	Ground
3	W_CLK	Word clock input for serial data
4	FQ_UD	Frequency update input
5	DATA	Serial data input
6	RESET	Reset input (active high)
7-14	NC	No connection
15	REF_CLK	Reference clock input (up to 125 MHz)
16	DAC_OUT	Analog sine wave output
17	COMP1	DAC comparator input 1
18	COMP2	DAC comparator input 2
19	IOUT	Current output for sine wave
20	GND	Ground
21-28	NC	No connection

Usage Instructions

How to Use the AD9850 in a Circuit

Power Supply: Connect the VCC pin to a stable power source (2.7V to 5.5V) and the GND pin to ground.
Reference Clock: Provide a stable reference clock signal to the REF_CLK pin. A crystal oscillator or external clock source can be used.
Serial Communication: Use the W_CLK, FQ_UD, DATA, and RESET pins to configure the frequency and phase of the output waveform. These pins are controlled via a microcontroller or FPGA.
Output Waveform: The sine wave output is available at the DAC_OUT pin, while the square wave output can be derived from the IOUT pin.

Important Considerations

Use decoupling capacitors (e.g., 0.1 µF) near the VCC pin to reduce noise.
Ensure the reference clock signal is clean and stable for accurate frequency generation.
Avoid exceeding the maximum input voltage or current ratings to prevent damage.
Use proper termination for the output signals to maintain signal integrity.

Example: Connecting AD9850 to Arduino UNO

The AD9850 can be easily interfaced with an Arduino UNO for frequency generation. Below is an example code to generate a 1 MHz sine wave:

// Include necessary libraries
#include <SPI.h>

// Define AD9850 control pins
#define W_CLK 8    // Word clock pin
#define FQ_UD 9    // Frequency update pin
#define DATA 10    // Serial data pin
#define RESET 11   // Reset pin

void setup() {
  // Set control pins as outputs
  pinMode(W_CLK, OUTPUT);
  pinMode(FQ_UD, OUTPUT);
  pinMode(DATA, OUTPUT);
  pinMode(RESET, OUTPUT);

  // Initialize pins
  digitalWrite(W_CLK, LOW);
  digitalWrite(FQ_UD, LOW);
  digitalWrite(DATA, LOW);
  digitalWrite(RESET, LOW);

  // Reset the AD9850
  digitalWrite(RESET, HIGH);
  delay(1);
  digitalWrite(RESET, LOW);

  // Set frequency to 1 MHz
  setFrequency(1000000); // Frequency in Hz
}

void loop() {
  // The AD9850 will continuously output the set frequency
}

// Function to set frequency
void setFrequency(unsigned long frequency) {
  unsigned long tuningWord = (frequency * pow(2, 32)) / 125000000; 
  // Calculate tuning word based on reference clock (125 MHz)

  for (int i = 0; i < 4; i++) {
    shiftOut(DATA, W_CLK, LSBFIRST, tuningWord & 0xFF);
    // Send 8 bits of the tuning word (LSB first)
    tuningWord >>= 8; // Shift to the next byte
  }

  shiftOut(DATA, W_CLK, LSBFIRST, 0x00); // Phase word (default 0)
  digitalWrite(FQ_UD, HIGH); // Update frequency
  digitalWrite(FQ_UD, LOW);
}

Notes:

Replace the reference clock frequency in the setFrequency function if using a clock other than 125 MHz.
Ensure proper connections between the Arduino and AD9850 pins.

Troubleshooting and FAQs

Common Issues

No Output Signal:
- Verify the power supply and ground connections.
- Ensure the reference clock signal is present and within the specified range.
- Check the serial communication pins for proper connections.
Incorrect Frequency Output:
- Confirm the reference clock frequency matches the value used in calculations.
- Verify the tuning word calculation in the code.
High Noise in Output Signal:
- Use proper decoupling capacitors near the power supply pins.
- Ensure the output signal is terminated correctly.

FAQs

Q: Can the AD9850 generate square waves directly?
A: Yes, the AD9850 can generate square waves using the IOUT pin. However, additional circuitry may be required to condition the signal.

Q: What is the maximum frequency the AD9850 can generate?
A: The AD9850 can generate frequencies up to 62.5 MHz for sine waves, which is half of the reference clock frequency (Nyquist limit).

Q: Can I use a lower reference clock frequency?
A: Yes, the AD9850 supports reference clock frequencies below 125 MHz, but this will reduce the maximum output frequency and resolution.

Q: How do I improve phase noise performance?
A: Use a high-quality, low-jitter reference clock source and ensure proper grounding and decoupling in the circuit design.