Question about LM3424 external synchronization PWM Pulse width

Genius 4220 points

Other Parts Discussed in Thread: LM3424

Hi,

The description about external synchronization signal pulse width In LM3424 D/S page14

"SWITCHING FREQUENCY" section (It should have a pulse width of 100ns),

Is there any indication of the range of this Pulse width?

Thanks,

over 11 years ago

0 Victor Chen_HK over 11 years ago

TI__Expert 5130 points

Edited as it is wrong.

0 Go over 11 years ago in reply to Victor Chen_HK

Genius 4220 points

Hi, Victor

Thank you for your prompt reply.

I've heard before that the pulse width of external sync signal should be around 100ns in any switching freq setting

because the DC level of RT pin must be stable before the next sync signal and a wide pulse might affect

the DC level of RT pin.

Is this understanding correct?

Thanks,

0 Victor Chen_HK over 11 years ago in reply to Go

TI__Expert 5130 points

Hello Go,

I think my pervious understanding could be wrong. I will double check on that and let you know later.

Thanks.

Victor

0 Victor Chen_HK over 11 years ago in reply to Go

TI__Expert 5130 points

Hi Go,

Your understanding is correct. It is always recommended to use a small pulse like 100ns for the external sync, otherwise the synchronization won’t work right. Even though there is a range, it is small. So please just stick to the datasheet information and use 100ns for the PWD signal.

Thanks.

Victor

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Question about LM3424 external synchronization PWM Pulse width