74lvc3245 ??
--- In "teohoeeng" <> wrote:
>
> Thanks. I have looked at the MAXIM 300X datasheets you indicated. But I think
> its Vih is too high for TTL level. The data sheets also seems to suggest it
> is more for CMOS interface than TTL. I can't find any 3.3V TTL to 5V TTL
> level shifter in maxim website...all those chips are meant for CMOS which has
> a very high VIh compared to TTL.
>
> So difficult to find one suitable one....But I like the maxim 300X series
> which allows bi-directional data transfer without needing direction bit, and
> the interface is neat, requiring only power supply and data bit lines. No
> need any cumbersome clk signal....
>
> One strange thing is that from tech support in TS, they said that the serial
> port on TS7800 3.3V TTL is 5V tolerant upon OS bootup and I have checked that
> those VIH, VOH, VIL and VOL for 3,3V and 5V TTL are the same. If that's the
> case, it seems to suggest I shouldn't need any translator at all...but I can
> TX to sensor but receive garbage from sensor....
>
> Still searching....Have anyone else tried any level shifter successfully from
> TS7800 3.3V TTL to 5V TTL serially (bi-directional)
>
> --- In "Theodore A. Roth" <taroth@> wrote:
> >
> > On Sat, Mar 14, 2009 at 4:45 PM, teohoeeng <teohoeeng@> wrote:
> > > Yes, I want to interface between 3.3V TTL UART and 5V TTL UART without
> > > using any RS232 shifter to reduce hardware parts. I am only concern with
> > > 3 lines, TX, RX and GND.
> > >
> > > In fact, my 5V TTL sensor can receive data possibly because the 3.3V
> > > logic output still meet 5V TTL input requirements, but not the other way
> > > round, that's why I cannot receive the data out from 5V sensor output
> > > into the TS7800 3.3V TTL UART. I think I just need to meddle with this RX
> > > line and leave the TX line untouched. I am reading my old digital system
> > > notes now ot review those Voh, Vih, Ioh, Iih which I have to use to size
> > > up the interface circuits or resistor....
> > >
> > > I also read in maxim website that simple resitor voltage divider with
> > > diode can help to do that...but I just want to verify by calculting if
> > > the resistors used will be compatible to my interface...
> > >
> > > I believ there are some standard resistance values to use for 3.3V TTL to
> > > 5V TTL serial interface to use...I am checking and trying to calculate
> > > now....
> >
> >
> > I've used a MAX3100E (a bi-directional level shifter) to interface a
> > 2.8V gsm modem uart to 3.3V lpc2378 uart. The gsm modem was not 3.3v
> > tolerant. The MAX300X devices have a 1.2V - 5.5V range on VL and 1.65V
> > - 5.5V VCC range. Should easily work for your application.
> >
> > http://www.maxim-ic.com/quick_view2.cfm/qv_pk/3672
> >
> > Ted Roth
> >
>
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