VHF low level to TTL converter

As Fred says, the 74ACT163 isn't fast enough to deal with 120MHz - the maximum guaranteed count rate for a single device is about 110MHz, and if you want to count more than 16 transitions, the carry propagation delays and counter enable set-up times pull you back to about 50MHz.

ECL can be a lot faster. Look at Motorola/ON-Semiconductor's ECLinPS counters which can offer 500MHz counting for more or less unlimited numbers of digits.

There are comparators around that can handle these sorts of frequencies, mostly derived from the old Am685 which fell over at about

100MHz, but all the ones I know of need +/-5V rails (or +5V/-4.5V) and produce ECL output levels (-0.8V high, -1.6V low).

ECL line receivers can cope with the frequency, and - since your 0.8V swing is exactly one ECL voltage swing - they can certainly cope with the amplitude, but the DC signal levels you specify are hard to get at.

As Fred says, you can use capacitative coupling to shift the signal to a range inside the common mode range, or you could use a discrete transistor level shifter biult with somehting like the BFT93 5GHz PNP wideband transistor

which you can buy off the shelf from Farnell and similar broadline distributors.

----------- Bill Sloman, Nijmegen

This is a phemonemal comparator for under 50 cents:

This particular part has a rated Vcc of 3.6 volts max, which would drive an ACT load fine, but you'd need another (wimpy) supply. Most of the LVDS receivers work fine with common-mode inputs down to ground, so you could ground one input and ac couple into the other, or bias one up to +0.4 and run your sig into the other.

There are some 5-volt equivalents, National maybe, but they tend to be a bit slower, although you have a pretty healthy drive level, which speeds them up a bit.

You could also use a fast TinyLogic inverter: AC couple your signal to its input and add a big resistor from output to input to servo the DC operating point. Even cheaper, maybe.

John

--
62.5 MHz typical for a 5V supply and 50mV of overdrive, so neither
one will work. :-(


On the bright side of things,  Analog devices has a nice PECL
comparator:

http://www.analog.com/UploadedFiles/Data_Sheets/699026082ADCMP551_2_3_0.pdf

Which can be teamed up with your suggestion of ON Semi\'s MC100EPT21
to get the OP what he needs.  On Semi also has some nice PECL
comparators, but take a look at the prices!!!

The only issue I see that\'s left is that the counter wants to be
driven with 4.5 to 5.5V and the PECL parts want to see about 3.3V,
so an LM3940 ought to take care of that.

I've made a lot of money off running ACT163's at 125 MHz, namely in my clone of the LeCroy 4208 1ns TDC, which got me into the high-speed business.

But I wouldn't do it again, especially now when cheap CPLDs and FPGAs are so fast... as fast as, or faster than, 10KH ECL with far less hassle.

One way to get performance+revenue is to violate abs max specs.

John

--
John Fields
Professional Circuit Designer

The 5V logic is not fast enough for this bandwidth. That level of signal and frequency are comfortably handled by 3.3V logic and the LVPECL->LVTTL translator MC100EPT21, with a minimum maximum frequency of

275MHz, differential signal amplitude of 150mV to 1200mV, external Vbb ( for capacitive coupling ), and incredible input common range.

That link gives me an error...

Very nice- the maximum toggle is 80MHz though- how does that compare to the LT1719?

I've seen it done. In one case the circuit stopped working every year or so, because the propagation delay of one the TTL integrated circuits would shift enough that he'd have to swap in another part or two until system back on song - feasible for a universiyt one-off, but I got a lower jitter output by resychronising the the critical edge in ECLinPS, and shipping back into the system with an 100K125 ECL-to-TTL converter.

I prefer to solve that sort of problem with a bare minimum of ECL and - if necessary - a few level-shifting broadband transistors.

The one really nice thing about ECL logic is that you can organisie it for minimal grass on the power rails, which means that the analog parts of your circuit see a lot less radiated noise, and you can sometimes get away with powering them from a (well-filtered) digital power rail. The is the main reason why very fast A/D converters have balanced ECL-level outputs.

Admttedly, my party piece had more power rails than you could shake a stick at +/-25V for some high voltage analog, +/-15V for regular analog, locally regulated down to +/-7V for some very fast analog (up to 500MHz and probably good to 1GHz, though we couldn't test that), +5V for TTL, -5.2V for ECL and GaAs, -3,4V for the GaAs, and -2V for the terminating resistors on the ECL and the GaAs parts. The switching suppllies that set up most of the rails were pretty efficient, but the rack needed a lot of cooling.

------------------- Bill Sloman, Nijmegen

Dear all I want to convert 0.8V P-P (50 ohms), centred on 0.4V DC to TTL logic levels, from about 1 to 120 MHz.(input to a 74ACT163 binary counter) Whats the best/cheapest way of doing this, preferably with a single +5V supply and low current? Linearity is not critical I thought of using a video amp, but it would need dual supplies.

Thanks in advance

Richard

Just AC couple into "AZ100ELT21" found at

...Jim Thompson

--
|  James E.Thompson, P.E.                           |    mens     |
|  Analog Innovations, Inc.                         |     et      |
|  Analog/Mixed-Signal ASIC\'s and Discrete Systems  |    manus    |
|  Phoenix, Arizona            Voice:(480)460-2350  |             |
|  E-mail Address at Website     Fax:(480)460-2142  |  Brass Rat  |
|       http://www.analog-innovations.com           |    1962     |
             
I love to cook with wine.      Sometimes I even put it in the food.

How high in frequency will that one go? Isn't the AZ100EL16 faster (although it does draw twice the current, 18mA compared to 9mA)?

--
 Thanks,
    - Win

Synthesiser or frequency counter?

Do you need full count output or can you survive on a submultiple of the VHF input e.g. /4 or /10?

For counter preamp with speed, in the "good old days" we used the MC10216 triple line receiver as a limiting amp. Nowadays the 10116 seems still available, but as you'd appreciate that generation of ECL was thirsty.

Several hundred MHz.

OP wanted Sine to TTL/CMOS, AZ100EL16 part is differential-to-PECL.

...Jim Thompson

--
|  James E.Thompson, P.E.                           |    mens     |
|  Analog Innovations, Inc.                         |     et      |
|  Analog/Mixed-Signal ASIC\'s and Discrete Systems  |    manus    |
|  Phoenix, Arizona            Voice:(480)460-2350  |             |
|  E-mail Address at Website     Fax:(480)460-2142  |  Brass Rat  |
|       http://www.analog-innovations.com           |    1962     |
             
I love to cook with wine.      Sometimes I even put it in the food.

ELT21 has TTL outputs. And the AZmicro part is a lot better than the original Moto/Onsemi version, which is downright buggy.

John

_CMOS/TTL_ Outputs. Rail-to-rail. Designed by a bright young fellow named Earl Schreyer (with me advising over his shoulder :-) Earl is now at Fairchild, San Diego (at last contact).

...Jim Thompson

--
|  James E.Thompson, P.E.                           |    mens     |
|  Analog Innovations, Inc.                         |     et      |
|  Analog/Mixed-Signal ASIC\'s and Discrete Systems  |    manus    |
|  Phoenix, Arizona            Voice:(480)460-2350  |             |
|  E-mail Address at Website     Fax:(480)460-2142  |  Brass Rat  |
|       http://www.analog-innovations.com           |    1962     |
             
I love to cook with wine.      Sometimes I even put it in the food.

This is a newsgroup; nobody here is like their real selves. I suspect that some of you don't exist at all.

John

--
Advising?  More like pontificating, if your real life is anything
like the face you present here.

Particularly Fields... he's nothing but a fart in the Austin wind ;-)

However I still don't understand his intense hostility.

Except for dealing with leftist weenies I'm really a very pleasant fellow. Ask ANYONE who has ever worked for me, or with me for that matter.

Fields, Call (or E-mail) Earl Schreyer for instance, or qrk/Mark, or hundreds of names I can provide... I'd double-dog dare you, but you don't have the balls ;-)

...Jim Thompson

--
|  James E.Thompson, P.E.                           |    mens     |
|  Analog Innovations, Inc.                         |     et      |
|  Analog/Mixed-Signal ASIC\'s and Discrete Systems  |    manus    |
|  Phoenix, Arizona            Voice:(480)460-2350  |             |
|  E-mail Address at Website     Fax:(480)460-2142  |  Brass Rat  |
|       http://www.analog-innovations.com           |    1962     |
             
I love to cook with wine.      Sometimes I even put it in the food.

John Larkin said

I do. You can see me nightly on Fox.