LM2903-Q1: LM2903 | Loading Issue

Subrahmanyam V

Part Number: LM2903-Q1
Other Parts Discussed in Thread: UCC27712, LM2903, TLV1805

Hi,

I am generating complimentary pulses using LM2903 by comparing the modulation signal with the saw-tooth. These are fed to UCC27712 as HI and LI.

What I noticed is a capacitive loading effect on the bottom pulse which is delaying the rise time of the pulse. Further reducing the pull-up resistor of comparator is not helping in anyway.

In order to use a buffer between the comparator output and the Gate driver, what factors should I consider apart from the slew rate and increased capacitive loading?

Can someone suggest me a good part-number to use which is less susceptible for capacitive loading and can still operate at high switching frequencies like 500 kHz?

Thanks in advance,

Subrahmanyam

over 3 years ago

0 Chuck Sins over 3 years ago

TI__Mastermind 23395 points

What is your operating voltage? It would be preferable to use a comparator with a push pull output stage.

Chuck

0 Subrahmanyam V over 3 years ago in reply to Chuck Sins

Intellectual 430 points

My operating voltage for the IC is 14.4 V.

0 Chuck Sins over 3 years ago in reply to Subrahmanyam V

TI__Mastermind 23395 points

Our TLV1805 would offer the best response since it can handle the 14.4V operating voltage and it has a push pull output stage.

It is available as a single channel only, so it would require two devices if you need two channels.

Chuck

0 Subrahmanyam V over 3 years ago in reply to Chuck Sins

Intellectual 430 points

Hi Chuck,

When the gate driver is symmetrical for both signals, why will the LI signal only will have loading as such?

If loading were to happen, HI and LI should load equally! Isn't it?

0 Chuck Sins over 3 years ago in reply to Subrahmanyam V

TI__Mastermind 23395 points

Sorry, at this point you will need to show your circuit and waveform so we can better support you.

By switching to a push pull output stage, the output waveform will be more symmetrical then if you use an open collector device.

If the capacitive loading problem is occurring at the input, this will not help. So please share your circuit and waveforms.

Thanks

Chuck

0 Chuck Sins over 3 years ago in reply to Chuck Sins

TI__Mastermind 23395 points

There has not been a new post on this thread for a while, so I will be closing it.

If you need additional support, please reply or open a new post

thanks

Chuck

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LM2903-Q1: LM2903 | Loading Issue