How to generate a 50 Mhz clock for TTL circuit

L

Lathe_Biosas

Guest
Hi

Could anyone share some ideas or source of information on how to build
a circuit to generate a 50 Mhz clock for a TTL circuit?

Best Regards
 
"Lathe_Biosas" <lathe_biosas@hotmail.com> wrote in message
news:1109202236.996652.189250@l41g2000cwc.googlegroups.com...
Hi

Could anyone share some ideas or source of information on how to build
a circuit to generate a 50 Mhz clock for a TTL circuit?

Best Regards

http://www.foxonline.com/
Click to expand...
etc

(Google is your friend, as they say).

Ken
 
On 23 Feb 2005 15:43:57 -0800, the renowned "Lathe_Biosas"
<lathe_biosas@hotmail.com> wrote:

Hi

Could anyone share some ideas or source of information on how to build
a circuit to generate a 50 Mhz clock for a TTL circuit?

Best Regards
Click to expand...
What do you want that's different from a modestly priced "canned"
50MHz xtal oscillator?

A resonator, an unbuffered single inverter and a resistor could be
cheaper.
 
A listing of Oscillator manufacturers:
http://www.interfacebus.com/oscillators.html
 
Spehro Pefhany wrote:
What do you want that's different from a modestly priced "canned"
50MHz xtal oscillator?

A resonator, an unbuffered single inverter and a resistor could be
cheaper.
Click to expand...

Hi,

Thank you very much for your answer.
I have the SG-51 and SG-531 @ 50.00 Mhz
http://www.eea.epson.com/go/Prod_Admin/Categories/EEA/QD/Crystal_Oscillators/all_oscillators/displayItem?itemId=SG-51&categoryId=EEA.QD.Crystal_Oscillators.all_oscillators

Question:
If I wire the terminals V_DD to 5 volts, the GND to ground then it will
generate a clock signal on the OUT pin of 50 Mhz to make a TTL counter
work at that frecuency? (Sorry I haven't wired because I'm afraid to
burn it)

Best Regards
 
On 23 Feb 2005 18:27:23 -0800, the renowned "Lathe_Biosas"
<lathe_biosas@hotmail.com> wrote:

Spehro Pefhany wrote:
What do you want that's different from a modestly priced "canned"
50MHz xtal oscillator?

A resonator, an unbuffered single inverter and a resistor could be
cheaper.


Hi,

Thank you very much for your answer.
I have the SG-51 and SG-531 @ 50.00 Mhz
http://www.eea.epson.com/go/Prod_Admin/Categories/EEA/QD/Crystal_Oscillators/all_oscillators/displayItem?itemId=SG-51&categoryId=EEA.QD.Crystal_Oscillators.all_oscillators

Question:
If I wire the terminals V_DD to 5 volts, the GND to ground then it will
generate a clock signal on the OUT pin of 50 Mhz to make a TTL counter
work at that frecuency?
Click to expand...
Yes, assuming it's designed for 5.0V (not 3.3V or whatever) and
assuming the TTL counter can clock that fast.

For example, an SN7490 might only be able to clock at 32MHz, a 74HC74
has a max toggle frequency of only 25MHz @~5V over temperature etc.
Fast "TTL" logic families can do 50MHz easily.

(Sorry I haven't wired because I'm afraid to
burn it)

Best Regards
Click to expand...
 
Spehro Pefhany wrote:
Yes, assuming it's designed for 5.0V (not 3.3V or whatever) and
assuming the TTL counter can clock that fast.

For example, an SN7490 might only be able to clock at 32MHz, a 74HC74
has a max toggle frequency of only 25MHz @~5V over temperature etc.
Fast "TTL" logic families can do 50MHz easily.
Click to expand...
Great, thanks for the helpful information

The TTL is a 74HC4040 on page 5 of product specification
http://www.semiconductors.philips.com/pip/74HC4040.html
shows +25° C @ 82 Mhz @ 4.5 Volts, so I think the chip won't run
so hot at 50 Mhz

Best Regards
 
Hi again

The crystal oscillator was wired, the signal is sinusoidal.
How do I make the signal a square pulse to clock the TTL?

Regards
 
Lathe_Biosas wrote:
Hi again

The crystal oscillator was wired, the signal is sinusoidal.
How do I make the signal a square pulse to clock the TTL?

Regards
Click to expand...
It doesn't matter that the signal looks sinusoidal. I assume the
output oscillates between 0V and Vdd (at 50 MHz)? correct?

The output will still cross the TTL transition voltages (or in your
case the HCMOS transitions) at 50 MHz +/- the tolerance of the
oscillator you purchased, with the jitter spec. of the oscillator you
purchased.

Your counter will run at 50 MHz.
 
Quite true, John but I didn't see what scope he was using to look at
his signal. My Tek 475 at full bandwidth would give a reasonable
display but a slower scope would round off his squarewave. I've been
using a 32 MHz canned oscillator that makes quite nice squares,
considering the 475 can only show the harmonics up to 250 MHz.
GG
 
tlbs wrote:
Lathe_Biosas wrote:
Hi again

The crystal oscillator was wired, the signal is sinusoidal.
How do I make the signal a square pulse to clock the TTL?

Regards

It doesn't matter that the signal looks sinusoidal. I assume the
output oscillates between 0V and Vdd (at 50 MHz)? correct?
Click to expand...
Setup: FLUKE 192B Scopemeter 60 Mhz 500 MS/s

The output oscillates as follows:

Scope: Channel A 200 mV - 10 ns
Peak Max: 0.63 V
Peak Min: -0.24 V
Peak-Peak: 0.84 ~ 0.91 V

Multimeter: V_out= 2.476 Volts

Your counter will run at 50 MHz.
Click to expand...
Great. I was on the verge of buying an LMV7219
http://www.national.com/pf/LM/LMV7219.html to build
the circuit to get the square wave.

Thank you and best regards
 
Hi,

The clock signal is only for the counter, the counter will feed other
TTLs

Regards
 
Setup:
FLUKE 192B Scopemeter 60 Mhz 500 MS/s
Channel A = 200 mV - 10ns
 
That means that the signal is square but as I have only a 60Mhz Scope,
it is only possible to see a sinosoidal signal?
 
Lathe_Biosas wrote:
That means that the signal is square but as I have only a 60Mhz Scope,
it is only possible to see a sinosoidal signal?

Not only possible, but pretty near assured.
Click to expand...
 
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