i'm making a new smps so i've tested the PWM chips with my new scope 
and something weird was happening :
output B was ok and output A had spikes only , no square wave
i tried both the sg3525 and the uc2825 and the same thing was happening , only one output is working
and it was output B on both chips ...
i've changed the chips million times , and was going like
finally i found the problem
, i used 2 regular BNC cables with the scope , i've changed one to a 60mhz probe and it started to work .
now i have couple questions :
both outputs of the chip are identical ,how can it be that out B is working with normal probe and out A isnt?
the same is happening with sg3525 ...
update :
i have added a 1K resistor in series with a normal BNC and it worked fine , what is going on here ?
also , do u think i've damaged the chips?
and something weird was happening :
output B was ok and output A had spikes only , no square wave
i tried both the sg3525 and the uc2825 and the same thing was happening , only one output is working
and it was output B on both chips ...i've changed the chips million times , and was going like
finally i found the problem
, i used 2 regular BNC cables with the scope , i've changed one to a 60mhz probe and it started to work .now i have couple questions :
both outputs of the chip are identical ,how can it be that out B is working with normal probe and out A isnt?
the same is happening with sg3525 ...
update :
i have added a 1K resistor in series with a normal BNC and it worked fine
, what is going on here ? also , do u think i've damaged the chips?
i figured out what was the problem .....
i used an old pc power supply and didnt use any caps on the Vcc pin of the chip , so when i was connecting the probe the signal stopped because in a split of a second the voltage dropped because of the load (the probe) and the chip entered under voltage lockout condition
it started to happen on output b also , then i figured it
now all working fine , even with a regular probe
so i didnt damage anything
i used an old pc power supply and didnt use any caps on the Vcc pin of the chip , so when i was connecting the probe the signal stopped because in a split of a second the voltage dropped because of the load (the probe) and the chip entered under voltage lockout condition
it started to happen on output b also , then i figured it
now all working fine , even with a regular probe
so i didnt damage anything
What size cap did you use
I'm having the same problem, however I do not have a 60 Mhz probe. Should the circuit have a cap across the battery line, and if so what size. Also the SG3525 get loaded down with the scobe probe
but ok. That just seems kinda strange but ok. Any help with the circuit I will be more than happy.
Thank you
I'm having the same problem, however I do not have a 60 Mhz probe. Should the circuit have a cap across the battery line, and if so what size. Also the SG3525 get loaded down with the scobe probe
but ok. That just seems kinda strange but ok. Any help with the circuit I will be more than happy.Thank you
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