FTDI Cable

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BARRYGORDON
 
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Joined: Thu Sep 15, 2011 11:58 pm

FTDI Cable

Post by BARRYGORDON »

I just purchased the FTDI 3.3 volt cable. Although It states that it will work fine with 5 volt logic I am concerned. The system I will be using it with (Sirius SC-H1 satellite tuner) states its interface to be 5 volt TTL.

Does anyone know if this cable will work or do I need the FTDI 5 volt cable?

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Franklin97355
 
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Joined: Mon Apr 21, 2008 2:33 pm

Re: FTDI Cable

Post by Franklin97355 »

Most logic will switch around the half way point with hysteresis so the 3.3v would be OK for most logic and 0v is always OK.

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baldengineer
 
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Re: FTDI Cable

Post by baldengineer »

BARRYGORDON wrote:I just purchased the FTDI 3.3 volt cable. Although It states that it will work fine with 5 volt logic I am concerned.
What is the difference between the product description saying it will work okay and people on a forum? ;)

The chip inside actually runs on 5V. However, its output is only 3V. It can still accept input up to 5V. Since your device is 5V TLL, this works fine. A TTL input signal is defined as "low" when between 0 V and 0.8 V with respect to the ground terminal, and "high" when between 2.2 V and 5 V.

Table 4.3.2 of the datasheet linked to on the FTDI cable's product page, shows the Voh to be at least 2.2V.

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