SN74AVC32T245: High Density Voltage Translator

This device has two supply rails. The minimum is 1.2 V, but this will work with 1.1 V input signals.

Hi Clemens,

I'm not exactly following - is 1.2V referring to the minimum output or input voltage? Also do you mean that there is one supply rail for the input and one for the output? What pins are these?

Thanks,

Cam

The two supplies are V_CCA and V_CCB. Which is input or output depends on the DIR signals.

With an 1.2 V supply, V_IH is 0.78 V.

Hi Clemens, 

So just confirming my understanding; to achieve the application they need,

V_cca = 1.2V resulting in Vih=0.78V

V_ccb = 3.3V resulting in Vout = 3.3V if the input voltage is greater than 0.78V?

Also how did you get subscripts in to e2e!

Thanks,

Cam

Hey Cameron,

By "high density voltage translators", you are asking for a recommendation for translators with high bit count? If so, direction controlled families (i.e AXC, LXC, AVC, LVC) would benefit you the most in your application since they provide the highest bit count of any of the translators. 

As Clemens mentioned, the SN74AVC32T245 may work here however operation is not guaranteed if the supply goes under the minimum specification. AXC8T245 would work here since the operating voltage is from 0.65V to 3.6V. 

Cameron Perl said:

if the supply rail is 3.3, that limits the minimum voltage the device can accept as a 'High', right?

By "High" I am assuming you are referring to an input logic high. Below is the calculation used to solve VIH and VIL for your application.  

Regards,

Jack 

Hi Jack,

Correct - high density in this situation means high bit count in order to cut down on the number of devices needed to translate all 100-150 lines.

Do we have any AXC devices at >8 bit count?

Also to clarify, if Vcca=1.2V, are we invalidating the datasheet specifications with a 1.1V input to the device? That part is not really clear to me since this would put the minimum you highlighted at 0.78V as specified above which would be in tolerance according to the datasheet?

Sorry if I am misunderstanding something.

Thanks,

Cam

Hey Cam,

AXC devices support up to 8 bit max. 

Below is more information regarding the difference between Vcca and VIH. Supply voltage is used to power on the device, whereas input voltage (VI and VIH)  is used for input/output terminals.

Best,

Jack

Hi Jack,

So then as I said above, there would be no issue with the following comments for the SN74AVC32T245, right?

Vih minimum = Vcci *0.65 while Vcci is between 1.2V to 1.95V

Vi is specified as requiring the input voltage to be >0V

If Vcc_a is defined to be the input voltage through DIR signals and is set to 1.2V, the Vih minimum will be 0.78V. Vcc_b is defined to be the output voltage through DIR signals and is set to 3.3V.

This means any input above 0.78V will be translated to Vcc_b which is 3.3V.

Thanks,

Cam