[gta02-core] Telit 2.8 V logic

Werner Almesberger werner at openmoko.org
Wed Aug 19 15:30:35 CEST 2009

?lvaro Lopes wrote:
> Personally I prefer using some small level shifters. Like MAX13001E
> [1] 4x4UCSP (2mm x 2mm), 6 bit wide.

Hmm, that one is hard to source: neither Digi-Key, Mouser, nor Arrow
have it. But the Analog Devices ADG3304BCBZ (there's one on the WLAN
daugherboard already) should work too, Digi-Key have it, and it's
even smaller ;)


Unlike the MAX1300x, the ADG3304 has a power sequencing requirement,
but with the high side at "always on" IO_3V3, that's okay.

It has four channels, so it could control TXD, DTR, and RTS, and
have one channel available for other uses (or assign to RXD). RXD
and CTS are modem -> CPU, so they can be used unshifted.

> I don't like adding resistor dividers, they will make design more
> susceptible to EMI interference.

Yeah, that's why I suggestively put the three dots on the CPU side of
the network :-)

Anyone in favour of resistors ?

- Werner

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