Products > Test Equipment
Replacement for the PM9610 Prescaler for Philips PM6654 High precision Counter
david69:
You have true, LT is expensive, in package exacting for soldering
:(
I don`t know, but AD8313 in CONTROLLER MODE would be
controll directly divider MC12095? The scheme will be plainer
with this chip from Ebay?
david69:
Attempt for improve scheme
SaabFAN:
It generally should work, but I see a few problems:
- The MC12095 has it's input loaded with 56 Ohms. I made that mistake too and it just doesn't work. The sensitivity of the chip is extremely low if you put a resistor there. You need to place a DC-Block capacitor between the terminator and the input-pin of the Prescaler. It is an ECL-Circuit and has bias-voltage at the input-pin. Disturb that bias-voltage and the chip stops working correctly.
Also the DC-Block capacitors at the inverting inputs of the prescalers should match the capacitance of the other DC-Block caps.
- What's the purpose of R13? At 10 Ohms it will load down the output significantly. To have 5V across it, there needs to be a current of 500mA flowing through it. Way more than such a tiny chip can handle. If used at all, you can put 1k or 10k there. The SB-Input is relatively high impedance (as high as ECL-Inputs can be) and the AD8313 has a totem pole output-stage. If it want's the standby-pin to go LOW, it will pull it actively low, so no actual need for a pulldown-resistor.
- The detector and the Prescaler both have 50 Ohms termination, which results in a 25 Ohm load for the ERA-3 Amplifier, resulting in reduced amplitude. Made the same mistake and was pointed towards it by another forum-member. Replacing the termination-resistors with 100 Ohms resistors made the circuit work a lot better.
Also not so much a problem, but unecessary: You don't need a DC-Block capacitor at the output of the second Prescaler-chip. At that point you're connecting digital circuits, which generally speaking like their signals at either 0V or as close to Vcc as possible (in this case 5V).
david69:
Yes, R13 is mistake, I was thinking about 1K resistor. I will revork
output from MAR6. Thank You.
david69:
reworked scheme
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