Part Number: UCC27525
I am experiencing excessive output jitter from a UCC27525D dual MOSFET driver:
I have built a test circuit to explore this problem in its most basic form and it would appear that it is attributable to unexpected operation of the device itself.
The test circuit I used to examine this consists of a UCC27525D supplied from a 13V bench supply and with 10nF, 100nF and 10uF parallel power supply decoupling capacitors in close proximity to the device power pins and with good connections directly to the device ground/power pins (pin 3 and pin 6 respectively). A 3V square wave is injected into the non-inverting driver input pin (pin 4) via a short coaxial cable terminated in 51R directly at the test device. The input (pin 4) and output (pin 5) are monitored using a high-performance 1GHz bandwitdth oscilloscope (Agilent 9000 series) with locally earthed oscilloscope probes. The enables (pin 1 & pin 8) and unused inverting input (pin 2) to the device are left open circuit. There is no load other than the oscilloscope probe on the output being monitored.
The oscilloscope screen shots below were captured with colour grade enabled on the oscilloscope. This clearly shows a quantised varying delay (jitter) on both rising and falling output edges with respect to the associated input transition. These delays alternate each cycle between the two discrete delays.
It should be noted that this jitter effect starts to occur for input waveforms exceeding approximately 1MHz and varies in magnitude with the frequency of the input waveform.
TOP Trace = Input (Pin 4), BOTTOM Trace = Output (pin 5)
Any advice you can give to help resolve this problem would be very much appreciated.
In reply to Mateo Begue:
Oscilloscope screen shots:
Top traces = input (1V / division), Bottom traces = output (5V / division)
Time base = 5ns / division
In reply to Stuart Harley:
Yes the problem is also present with a capacitive load. I am in essence driving the gate of a FQP2N60 MOSFET through an isolation transformer.
Would you be able to repeat tests similar to the ones I performed in order to determine if you can reproduce the problem?
You were asking about power dissipation in the driver at 1MHz and if I had experienced device failures:
I am driving a much lower capacitive load than 10nF (i.e. gate of a FQP2N60 MOSFET through an isolation transformer). I have not experienced any device failures and I am actually driving at frequencies up to 3.2MHz. The board is forced air cooled. Thanks for your comment, I will investigate device power dissipation in more detail.
Have you been able to reproduce the jitter problem that I described?
I am getting very short of time on my project. Anything you can do to help resolve this problem would be very much appreciated.
Thanks for letting me know.
How long do you think it will take to get the samples and obtain test results?
Hi Stuart, I received the ICs today but did not have time to populate them onto a board. I will find time tomorrow and update you. Regards,Mateo
Thanks for the update. I look forward to your test results.
Have you been able to try the sample parts. I am getting very short of time on my project and need a solution as soon as possible. Anything you can do to speed things up would be very much appreciated.
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