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From: Winfield Hill
Subject: Re: Zero Crossing Circuit
Date: 2 Nov 2002 07:04:04 -0800
Organization: Rowland Institute
X-Newsreader: Direct Read News 4.00
>MUSTSEE ME wrote:
>> I am looking for a wideband zero-crossing detection circuit. I need to
>> detect zero crossing (both negative and positive crossing) of sine wave
>> at 100kHz-500kHz.
>> I have tried MAX907CPA, but the output is too noisy. Also, LM393 does
>> not give me a true zero crossing.
> If your application is sensitive to delay, comparator switching times
> depend on overdrive so you may need a pretty fast comparator. I'm using
> an LM319 for 88kHz in one application but it might have too much delay
> for you. For an application that was sensitive to delay I used a TI
> TL3016 in transparent mode (latch always enabled) at 52 MHz.
I like the MAX903 (8ns delay, compared to 40ns for the MAX907).
>You also have to define zero a bit loosely in that if there is noise,
>hysteresis will be essential. I have not used hysteresis with the
>TL3016. Separate positive and negative zero crossing signals really
>require two comparators for good delay matching.
A small amount of balanced hysteresis may work OK for the poor O.P.
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