[EE]: 3.3V-friendly TPIC6C595
Rob Robson
register/driver that could be driven by a micro running from 3.3V without
having to add a level converter. Has anyone used or found such an animal?
TIA,
RR
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Harold Hallikainen
> I'm looking for an equivalent to the venerable TPIC6C595 shift
> register/driver that could be driven by a micro running from 3.3V without
> having to add a level converter. Has anyone used or found such an animal?
>
> TIA,
> RR
>
I think http://allegromicro.com has some devices that operate at 3.3V, but
they have, as I recall, Darlington outputs that don't pull down very far.
So I used the part you mention (which I believe has FET outputs) and a
quad nand lvt as a level translator.
Harold
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Bob Axtell
> I'm looking for an equivalent to the venerable TPIC6C595 shift
> register/driver that could be driven by a micro running from 3.3V without
> having to add a level converter. Has anyone used or found such an animal?
>
> TIA,
> RR
>
>
>
makes them. I would avoid
Fairchild's version, too sensitive to noise for my blessing.
The device also buffers the signal well enough to drive external loads
easily...
--Bob A
Rob Robson
looking for. Unfortunately, I come up empty-handed when I search on that
(partial?) part number on the TI site or Digi-Key's. I can't find it by
doing a parametric search on TI's site either. Are you sure about the part
number?
Best regards,
RR
dpha...@telus.net
David
Rob Robson
needed for this application. VIh(min) for any of the TPIC6x595 family is
0.85 x Vcc (5V in this circuit), and the PIC is running at 3.3V.
Spehro Pefhany
>I'm looking for an equivalent to the venerable TPIC6C595 shift
>register/driver that could be driven by a micro running from 3.3V without
>having to add a level converter. Has anyone used or found such an animal?
If output drop is okay, I'd use a HC595 + ULN2803 .. cheaper and multiple
sourced... and more forgiving of layout.
>Best regards,
Spehro Pefhany --"it's the network..." "The Journey is the reward"
sp...@interlog.com Info for manufacturers: http://www.trexon.com
Embedded software/hardware/analog Info for designers: http://www.speff.com
Matt Pobursky
I think he probably means the SN74LV595A, which works down to Vcc=2V.
I suspect that you really want something that will interface directly with
low voltage (3.3V or less) and has a higher voltage output (5V).
I've been doing 3.3V and lower designs almost exclusively the past 5 years
or so and haven't run across such a beast yet. If you want to "do it right"
and not stretch any of the IC specs you'll have to go the level translator
route.
If your design is a one-off or hobbyist use then this is a pain. If it's a
production design then it can be done fairly cost effectively and take very
little PCB space.
Here are a couple methods which I have commonly used. Note the 1st circuit
is driving a TPIC6C595D (which is driving White LEDs in this case). ;-) The
second circuit is interfacing to a 5V only PLC communications bus
transceiver which has strict .85(Vcc) logic high levels.
http://www.mps-design.com/misc-images/leveltrans1.gif
http://www.mps-design.com/misc-images/leveltrans2.gif
The first circuit is quite economical as it's only two packages and the
74LVC07 can be had in a VSOP package if PCB real estate is important. Total
cost for production is probably about $.20 total. The circuit is speed
limited though since it uses open drain type drivers and is not the most
power friendly since it's switching a fairly stiff current through the
pullup resistors. In this application it didn't matter as the pullup
resistor current was << than the LED current.
The second circuit is a bit more costly (probably about $.35 total) but
still quite compact. Since all the drivers are active the speed performance
is excellent and static power dissipation is very low. The SN74LVC2T45DCTR
is bidirectional so that may be useful to you. TI also makes this part in
single gate and I believe quad gate parts as well. The quad gate part could
do all your required level shifting in one package, most likely. The
SN74LVC2G34DBV is a low voltage part with 5.5V tolerant inputs, comes in a
SOT23-6 package and is quite inexpensive. I'm quite sure they make a single
gate package as well.
Matt Pobursky
Maximum Performance Systems
Alan B. Pearce
>and multiple sourced... and more forgiving of layout.
especially as he is taking of driving relays. I don't think I would like to
drive relays directly from the outputs of any of the 595 family.
Bob Axtell
> Thanks, Bob. If it can drive small relays, it sounds exactly like what I'm
> looking for. Unfortunately, I come up empty-handed when I search on that
> (partial?) part number on the TI site or Digi-Key's. I can't find it by
> doing a parametric search on TI's site either. Are you sure about the part
> number?
>
> Best regards,
> RR
>
>
> ----- Original Message -----
> From: "Bob Axtell" <engi...@cotse.net>
> To: "Microcontroller discussion list - Public." <pic...@mit.edu>
> Sent: Saturday, January 26, 2008 4:32 AM
> Subject: Re: [EE]: 3.3V-friendly TPIC6C595
>
>
>
>> Rob Robson wrote:
>>
>>> I'm looking for an equivalent to the venerable TPIC6C595 shift
>>> register/driver that could be driven by a micro running from 3.3V without
>>> having to add a level converter. Has anyone used or found such an
>>> animal?
>>>
>>> TIA,
>>> RR
>>>
>>>
>>>
>>>
>> why not use the TLV595? It works at 3.3V admirably. Texas Instruments
>> makes them. I would avoid
>> Fairchild's version, too sensitive to noise for my blessing.
>>
Look at TI's
website and ask for scbd152b.pdf.
Sorry about that.
--BOB
Spehro Pefhany
>>>
> Hmmm. Its actually SN74LV595A. At 3.3V is guarantees 8mA sink or source.
> Look at TI's
> website and ask for scbd152b.pdf.
>
> Sorry about that.
>
> --BOB
TPIC6C595 will handle 250mA at 30V (100mA if all outputs are on
simultaneously).. it's essentially an HC595 with 8 avalanche-rated
DMOS open-drain transistors (one on each output).
Best regards,
Spehro Pefhany
--
"it's the network..." "The Journey is the reward"
s...@interlog.com Info for manufacturers: http://www.trexon.com
Embedded software/hardware/analog Info for designers: http://www.speff.com
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Bob Axtell
> Quoting Bob Axtell <engi...@cotse.net>:
>
>
>
>> Hmmm. Its actually SN74LV595A. At 3.3V is guarantees 8mA sink or source.
>> Look at TI's
>> website and ask for scbd152b.pdf.
>>
>> Sorry about that.
>>
>> --BOB
>>
>
> TPIC6C595 will handle 250mA at 30V (100mA if all outputs are on
> simultaneously).. it's essentially an HC595 with 8 avalanche-rated
> DMOS open-drain transistors (one on each output).
>
> Best regards,
> Spehro Pefhany
>
--Bob
William "Chops" Westfield
On Jan 28, 2008, at 6:57 AM, Spehro Pefhany wrote:
> TPIC6C595 will handle 250mA at 30V (100mA if all outputs are on
> simultaneously).. it's essentially an HC595 with 8 avalanche-rated
> DMOS open-drain transistors (one on each output).
I don't see anything in the spec sheet that makes the TPIC6C595
look at all "3.3V friendly": Vccmin = 4.5V, Vih = 0.85*Vcc = 3.8V...
BillW
Spehro Pefhany
>
> On Jan 28, 2008, at 6:57 AM, Spehro Pefhany wrote:
>
>> TPIC6C595 will handle 250mA at 30V (100mA if all outputs are on
>> simultaneously).. it's essentially an HC595 with 8 avalanche-rated
>> DMOS open-drain transistors (one on each output).
>
> I don't see anything in the spec sheet that makes the TPIC6C595
> look at all "3.3V friendly": Vccmin = 4.5V, Vih = 0.85*Vcc = 3.8V...
>
> BillW
Nope, not at all. It might be interesting to see what the operational
limits actually are. Maybe the logic part functions with 2V power, but
the DMOS transistors are not very "on" at 2V.
Best regards,
Spehro Pefhany
--
"it's the network..." "The Journey is the reward"
s...@interlog.com Info for manufacturers: http://www.trexon.com
Embedded software/hardware/analog Info for designers: http://www.speff.com
--