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'[PIC] results of 20MHz resonator tests'
2007\06\21@180730 by Bob Blick

face picon face
As promised.

I've just tested a handful of 20MHz ceramic resonators
with builtin caps. The board I tested it on has two
pics, one is connected to the resonator, the other is
a slave via a 100 ohm resistor from master's OSCOUT to
slave OSCIN. So it's tougher than your usual single
PIC setup.

The good news is, all the resonators I tested worked,
although I would not use some of them as you will see.
In case you don't know, these are all overtone
resonators. The fundamental (6.666 MHz) is
mechanically suppressed so no tank is required.

All these resonators are surface mount. Unfortunately
there is very little standarization in packaging.

Master PIC is a 16F876A set to HS mode. Slave is a
16F877A set to HS mode.

Scope probe is a Tektronix 6109B 100MHz x10 of unknown
capacitance, probably somewhere around 11 pF.

All the resonators are available at Digikey, since
they are fast and I have an account there :)

Enjoy the results!
-Bob

Panasonic EFJ-C2005E5B (digikey PA200CCT-ND)
1.0 mm pitch, marked with weird squiggly code
$0.41 in 100s
Starts and runs
If started with scope probe attached runs at
fundamental
Feedback amplitude lower than output

ECS ECS-HFR-20.00-B-TR (digikey XC1094CT-ND)
1.0 mm pitch, easy to read 20.00
$0.42 in 100s
Starts and runs
If started with scope probe attached runs at
fundamental
Feedback amplitude lower than output

ECS ECS-CR2-20.00-B-TR (digikey XC1109CT-ND)
1.5 mm pitch, marked 20.0M
$0.42 in 100s
Starts and runs even with scope attached to either
lead
High and balanced amplitude

Panasonic EFO-BM2005E5 (digikey PX200BCT-ND)
1.35 mm pitch, easy to read 20.0
$0.48 in 100s
Starts and runs even with scope attached to either
lead
Very high and balanced amplitude

TDK CCR20.0MXC7T (digikey 445-1649-1-ND)
1.0 mm pitch, 20 marked by laser hard to see
$0.42 in 100s
Starts and runs even with scope attached to either
lead
High amplitude, higher on feedback

Murata CSTCE20M0V53-R0 (digikey 490-1199-1-ND)
1.2 mm pitch, tiny metal package, marked in code E.e.
$0.53 in 100s
Starts and runs even with scope attached to either
lead
Very high and balanced amplitude

AVX PBRC-20.00HR (digikey 478-2114-1-ND)
2.5 mm pitch, marked 20.00Z
$0.62 in 100s
Starts and runs even with scope attached to either
lead
Very high amplitude, higher on feedback

--

2007\06\21@185328 by Marcel Duchamp

picon face
Great work, Bob! Thanks for sharing it with us.

A part similar to the last one on your list is the:
AVX PBRC-20.00BR with similar but slightly different specs.  Based on
what you showed, it probably needs testing to be called equivalent but
if it works for you, it is slightly less expensive.

Garrett Electronics has it:
www.garrettelec.com/cart/cart_add.cfm?part_no=PBRC-20.00BR
with pricing at $0.53/100's.  For people using resonators, price might
be important enough to try it out.

Bob Blick wrote:
{Quote hidden}

2007\06\22@015106 by Peter P.

picon face
Bob, thanks for sharing that,

did you notice that all the marginal resonators were physically smaller than the
ones that did work ? You listed them basically in order of increasing pad pitch.
Maybe there is a pattern here, related to the available oscillator gain in a PIC
? Did you try to test at reduced Vdd too ?

thanks,
Peter P.


2007\06\22@140950 by Bob Blick

face picon face

--- "Peter P." <spam_OUTplpeter2006TakeThisOuTspamyahoo.com> wrote:

> did you notice that all the marginal resonators were
> physically smaller than the
> ones that did work ? You listed them basically in
> order of increasing pad pitch.

When I started testing them I noticed it too, but the
TDK and Murata were very small and work well.

> Maybe there is a pattern here, related to the
> available oscillator gain in a PIC

I should have mentioned what it looks like with a
crystal and two 33pF caps attached. The feedback pin
has much lower amplitude, lower than any of the
resonators, while the drive pin is almost rail to
rail.

> ? Did you try to test at reduced Vdd too ?

Unfortunately the board I tested them with has its own
onboard switcher so I was stuck at 5 volts.

Cheerful regards,

Bob

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