AD9833 Signal Generator Overview
There is a digital microcircuit of a single-channel signal generator. called AD9833. In essence, this is an Up-Down counter to which a digital-to-analog converter is connected. This chip can be studied as part of the blue module
What do you need from the docks to get acquainted with AD9833?
No. | Name | number of pages |
1 | AN-1070 Application Note | 4 |
2 | Data Sheet AD9833 | 22 |
Pinout AD9833.
What is inside AD9833?
The basis of the chip is an Up-Down counter to which a 10-bit digital-to-analog converter is connected. Here you can see the ROM memory, which contains the calculated table of the sine function for one period. A multiplexer that chooses what to calculate: sin or saw. The MODE bit is responsible for this.
What configs does the AD9833 chip have?
Parameter | Explanation |
Frequency | signal frequency |
phase | Time shift of the signal. X-axis |
waveform | Waveform type, sine, sawtooth or square wave |
Here is a typical AD9833 IC connection diagram. Left SPI. On the right is the analog output. Also, AD9833 must be clocked with ethernet (ovsky) quartz at 25MHz
As usual, the body is microscopic 3×3 mm.
Software part
What mode does SPI work in? The chip is accessed when the FSYNC wire is 0V. The bits are latched on a negative edge (from 3.3V to 0V). Data is transmitted MSB first, MSB first (big-endian format).
Inside the chip is just a 16-bit shift register. The chip has no feedback. Here SPI only sends data one 2-byte word. There are 65536 ways to configure this register. The AD9833 chip itself does not respond. There is not even SPI here, not-before SPI.
SPI is needed in order to write internal registers. In total, there are actually 5 registers in the chip, 96 bit=12 byte configs.
Checking the chip in action.
Here is the sine. Umax: 0.57V Umin -0.059V
Here is the sawtooth signal
Here is the meander. A rectangular signal, by the way, is much higher in amplitude. As much as 2,882V
Possible application
As for me, the most basic application of the AD9833 chip is to clock some other microcircuit as part of a prototype while the printed circuit board of the main product is being developed. This is a universal quartz resonator with program control. Or you can ring the connectors where there are 50+ pins.
Conclusion
The chip is very minimalistic. You can’t change the amplitude, you can’t read the registers, you can’t test the chip. Plus, this chip has an original crutch: register registers with another register, and in parts. If possible, it is better to look at something else.
Acronym | Decryption |
DDS | direct digital synthesis |
NCO | numerically controlled oscillator |
DAC | digital-to-analog converter |
DAC | digital-to-analogue converter |
DSP | digital signal processor |
MSB | most significant bit |
LSB | least significant bit |