variable filter for varying square wave frequency
- Thread starter cktboy
- Start date
DickCappels
- Joined Aug 21, 2008
- 10,179
In Post #10 @Ian0 suggested the AD9833, a Direct Digital Synthesis generator chip from Analog Devices. If I had not missed the 4 MHz requirement I would have recommended that. I had a need for a wide range adjustable frequency source that could be programmed, and after A LOT of investigation and trying different approaches I settled on the AD9833. DDS generators have inherent jitter that is mainly a function of the clock rate and the output frequency. If you have an application that has very critical jitter requirements, Analog devices has a much faster synthesizer.
I talk to that with an ATMEGA48 using a 3 wire SPI interface. The chip can go up to 12.5 MHz with high frequency resolution and it generates sine or triangle waves by feeding a look-up table to the on-chip D-to-A converter. Analog Devices has much faster DDS chips too.
For example, have a look at eBay item #114505788924.
https://www.ebay.com/itm/114505788924
Alliexpress has them for a little bit left if you can buy from them.
@MrChips wrote:
Do you need 4MHz?
XR-2206 can output 1MHz sinewave and maybe 2MHz.
If you pass the 2 MHz sine wave through an analog squaring circuit you will make it a 4 MHz sine wave.
I talk to that with an ATMEGA48 using a 3 wire SPI interface. The chip can go up to 12.5 MHz with high frequency resolution and it generates sine or triangle waves by feeding a look-up table to the on-chip D-to-A converter. Analog Devices has much faster DDS chips too.
For example, have a look at eBay item #114505788924.
https://www.ebay.com/itm/114505788924
Alliexpress has them for a little bit left if you can buy from them.
@MrChips wrote:
Do you need 4MHz?
XR-2206 can output 1MHz sinewave and maybe 2MHz.
If you pass the 2 MHz sine wave through an analog squaring circuit you will make it a 4 MHz sine wave.
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