G
garyr
- Jan 1, 1970
- 0
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?
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?