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Looking for programmable clock generator IC, 1 Hz - 20 MHz

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andybrandi:
Hi! I'm looking for an IC to generate a clock signal for a DAC application (a personal project) that can be programmed to output arbitrary frequencies from roughly 1 Hz to 20 MHz. There is room for variation in the minimum frequency, but I need to get reasonably close to DC, and all of the affordable clock generator chips that I could find so far start at >1 kHz.

Further requirements:

- ideally no/few external components (although an input/reference clock signal is available, if needed)
- hand-solderable, bonus if DIP package
- programmable via SPI/I2C or similar
- reasonably low-cost (say < US$2)
- widely available in single quantities

Remarks:

- a single output channel is sufficient
- no constraints on output or supply voltage levels


Any suggestions? Admittedly, I could probably find one myself if I only searched for long enough, but if there's an obvious choice, I'd be happy to be enlightened.  :D Thanks!

MasterT:
In this price range only Si5351 comes to mind,
https://www.arrow.com/en/products/si5351a-b06208-gt/silicon-labs

ledtester:
The Si5351a is also widely available as a module, eg:

- https://www.adafruit.com/product/2045
- https://www.aliexpress.com/item/4000329085074.html
- https://www.ebay.com/itm/Si5351A-I2C-25MHZ-Clock-Generator-Breakout-Board-8KHz-to-160MHz-for-ArduinoRPA/313163663132


--- Quote ---There is room for variation in the minimum frequency, but I need to get reasonably close to DC, and all of the affordable clock generator chips that I could find so far start at >1 kHz.

--- End quote ---

You could route the signal through a divider for lower frequencies.

Renate:

--- Quote from: Si5351 datasheet ---Generates up to 8 non-integer-related frequencies from 2.5 kHz to 200 MHz
--- End quote ---

For the low frequencies you might need a phase accumulator DDS.
I like the AD9850, but that's a bit pricier.

ledtester:
For low frequency clocks you could just program a microcontroller to be a phase accumulator DDS - so the hardware cost might be zero if you have a spare uC board lying around.

For some pointers about this approach google "AVR DDS". The code and circuitry becomes a lot simpler if you just want to output a clock signal.

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