I'm trying to build a DDS VFO I've designed. Today I started adding parts to the board, first the voltage regulator. Voltage OK, 3.301 volts. Then I added a 50 MHz oscillator (CTS CB3LV); 3.3 volt line now measures 1 volt. Poking around a bit I find that the VCC and ground going to the oscillator chip are swapped (the pin numbers I assigned to the package drawing I created were incorrect). I remove the oscillator chip, make a few cuts and jumpers and reinstall the oscillator. Lo and behold! it works; sort of. My scope indicates that the frequency is right on but the output signal is not a square wave as expected and is much too large - it is now a sine wave having peak amplitude of positive 5 volts and negative 2 volts. A 200 ohm load reduces the output amplitude only slightly. The chip was obviously damaged but what damage would produce that kind of results?
10 years ago