TMS320F280049-Q1: Input pulse width 5ns

Hi Burak,

Burak Güvelioglu said:

1) Am I right?

Correct.

Burak Güvelioglu said:

Here it shows the minimum input pulse width as 110ns. 2) So when there is a 5ns pulse to its input, will the TMS320F28004x ignore this pulse? Can't detect it?

Correct. In HR mode, any pulses less than minimum requirement of 110ns will not be properly detected by the ECAP.

Burak Güvelioglu said:

3) I want to measure the width of a 5ns pulse. What do you recommend?

Unfortunately 5ns is too short even in regular ECAP mode which has a minimum requirement of 20ns on this device.

Thank you for your answer. That's exactly what I wanted to know... Well, what are your recommendations for detecting and measuring this 5ns pulse width?

Burak,

We don't have a C2000 device that can meet this requirement. The high MHz devices such as the AM243x should be able to do this though.

How flexible is the 5ns pulse measuring? Can it be extended to 10ns? If so, you can look at our 200MHz devices like F2838x which can measure 10ns.

I know I can read this in case of extending the signal. But then I need to know the exact width of the incoming pulse. For this reason, I never thought of expanding it.

Burak,

Thinking a bit more about this, another alternative is to use the F2838x device which has a resolution of 5ns. You will then use 2 ECAPs in tandem to capture the 5ns pulse. What I mean is you would synchronize 2 ECAPs and have one capture the rising edge and the other capture the falling edge. The 2nd ECAP triggers an interrupt where you perform the calculation to see if the delta between the 2 ECAP captures was 5ns so you can perform your action.

I think this could work. There will be slightly more software overhead here but should be fine if the frequency of your 5ns pulses is not too high.