What type of crystal should I use for the ATmega 32u4

Using Arduino Project Guidance
1

I am making a pcb with the ATmega 32u4 and I don't know what type of external crystal oscillator to use. should I use a 2 or 4 pin oscillator?

I want to do the least amount of SMD soldering so I don't want to get a crystal that has the pads underneath itself.

2

Either, but 4 pin have easier pads to solder.

3

Really? I saw some 4 pin crystals and they all have their pads underneath the actual crystal and the 2 pins were of the through hole kind. Also does the brand of crystal matter?

4

You asked for SMD!

No, brand does not matter, I suggest you start reading datasheets!

5

I think you misread my question, I said I want to do the least amount of SMD soldering. Thanks for the info, though.

6

Here is a sutiable crystal, $0.39. Don't forget the caps.

https://www.digikey.com/en/products/detail/ecs-inc/ECS-160-20-46X/2676589

But do you want a crystal, or crystal oscillator? They are not at all the same thing.

7

What would be better for the 32u4?

I think I would use the crystal oscillator, but I am not sure

8

A crystal oscillator has four pins and requires power and ground. Most people just use a crystal and two caps. The caps are chosen to match the specified load, in the case I linked, 20 pF total.

Design notes: How to calculate the value of crystal load capacit... - NXP Community

9

I see. I think I will use just a crystal and add some caps onto it.

10

The oscillator module will be substantially more expensive.

11

Is it ok to add caps to crystal oscillators, or can you only use caps with crystals

12

Use caps of the appropriate value, where required. They ARE required in many circumstances.

You will find some study of circuit design principles to be useful, if you intend to go further with this hobby.

13

This one, with two 22pF ceramic caps, seems to be what you are after.

14

This is not a relevant question! :face_with_raised_eyebrow:

A crystal oscillator incorporates all necessary components, it has only power, ground and an output of the specified frequency.

The connections to the actual crystal element are internal and completely inaccessible.

15

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