Which is better to use the MAX232 chip or a set of 1488/1489 serial line
drivers? I'm looking for stability and protection for the pic circut. I've
noticed that most commercial products still use the 1488/1489 pair instead of
max232's. is there a reason besides cheap??
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better to use the MAX232 chip or a set of 1488/1489 serial line
>drivers? I'm looking for stability and protection for the pic circut. I've
>noticed that most commercial products still use the 1488/1489 pair instead
of
>max232's. is there a reason besides cheap??
>
It's a lot less expensive in bulk. The max chip is ok, but beware of the
specs.
Their part rated at 115200, according to the reps we talked to, that means
that <SOME> of them will go that fast. They wouldn't guarantee a speed that
every part could achieve.
I know this seems counterintuitive, but we spent about half a day trying to
get
past this, then gave up.
I often use MAX242s, which are similar to the 232's but offer very low
power consumption.
Only 4 external 0.1 uF caps necessary.
eric
]
At 10:00 PM -0400 7/20/98, Timothy D. Gray wrote: {Quote hidden}
>Which is better to use the MAX232 chip or a set of 1488/1489 serial line
>drivers? I'm looking for stability and protection for the pic circut. I've
>noticed that most commercial products still use the 1488/1489 pair instead of
>max232's. is there a reason besides cheap??
>
>
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In message <.....XFMail.980720220033.timgrayKILLspam@spam@lambdanet.com>, "Timothy D.
Gray" <timgrayKILLspamLAMBDANET.COM> writes
>Which is better to use the MAX232 chip or a set of 1488/1489 serial line
>drivers? I'm looking for stability and protection for the pic circut. I've
>noticed that most commercial products still use the 1488/1489 pair instead of
>max232's. is there a reason besides cheap??
Reliability? I remember having problems with MAX232s getting zapped by
plugging and unplugging connectors with the power on.
Timothy Gray asked:
>Which is better to use the MAX232 chip or a set of 1488/1489 serial line
>drivers? I'm looking for stability and protection for the pic circut. I've
>noticed that most commercial products still use the 1488/1489 pair instead of
>max232's. is there a reason besides cheap??
If you're going to use 1488/1489, you will have to have +/- 12 Volts
available on the board. The advantage of using these chips is not only that
they're cheaper than MAX232s, but they use up less real estate on the final
product (more drivers/receivers per chip and no need for 5x external caps
per chip).
If this is a one off, go to the Maxim site and pick the part that has
exactly the features you want (ie internal caps, 5 output 5 input, etc.) and
get them to send you a few samples.
I've never had reliability problems (ie ESD) with Maxim parts, but I could
be lucky.
For all of my latest projects; I short DTR/DSR and CSR/RTS on the board and
use a Dallas Semiconductor DS275 (which "steals" negative voltage from the
device you're communicating to) and essentially create a three-wire RS-232
interface. This is the simplest, smallest, cheapest and lowest power
solution that I've found. I haven't had any problems with it up to 19,200
bps.
myke
Twenty nine years ago this week, Neil Armstrong walked on the moon for the
first time, this week in myke's Book Room,
They are cheap fuses. Always do the 1488/89 in DIP sockets. They WHEN
they blow, they are much easier to replace.
Andy
==================================================================
Andy Kunz - Statistical Research, Inc. - Westfield, New Jersey USA
==================================================================
>>>max232's. is there a reason besides cheap??
>
>They are cheap fuses. Always do the 1488/89 in DIP sockets. They WHEN
>they blow, they are much easier to replace.
>
>Andy
>
>==================================================================
>Andy Kunz - Statistical Research, Inc. - Westfield, New Jersey USA
>==================================================================
>
>
Ohh good point! my devices will be powered up all the time and then have
a laptop plugged in at service time (not shutting off the device) I'll do
the quad driver/reciever route then.
> Reliability? I remember having problems with MAX232s getting zapped
by > plugging and unplugging connectors with the power on.
>
> Leon
> --
> Leon Heller: leonspam_OUTlfheller.demon.co.ukhttp://www.lfheller.demon.co.uk
> Amateur Radio Callsign G1HSM Tel: +44 (0) 118 947 1424
> See http://www.lfheller.demon.co.uk/dds.htm for details of a simple AD9850
> DDS system. See " "/diy_dsp.htm for a simple DIY DSP ADSP-2104 system.
>
David, MAXIM's data sheets rate the MAX232 at 20K and the MAX232A at
116K. For rates up to 115K, the MAX202 is fairly popular. Considering
cost, if I was on a project where I was forced to go back to 1488/89's, I
would remove myself from the project... Given a 5V system, I simply
could not justify the extra power supply to support the older chips.
- Tom
At 09:08 PM 7/20/98 -0500, David VanHorn wrote: {Quote hidden}
> better to use the MAX232 chip or a set of 1488/1489 serial line
>>drivers? I'm looking for stability and protection for the pic circut. I've
>>noticed that most commercial products still use the 1488/1489 pair instead
>of
>>max232's. is there a reason besides cheap??
>>
>
>
>It's a lot less expensive in bulk. The max chip is ok, but beware of the
>specs.
>Their part rated at 115200, according to the reps we talked to, that means
>that <SOME> of them will go that fast. They wouldn't guarantee a speed that
>every part could achieve.
>
>I know this seems counterintuitive, but we spent about half a day trying to
>get
>past this, then gave up.
>
>
Tom Handley
New Age Communications
Since '75 before "New Age" and no one around here is waiting for UFOs...
> David, MAXIM's data sheets rate the MAX232 at 20K and the MAX232A at
>116K. For rates up to 115K, the MAX202 is fairly popular. Considering
>cost, if I was on a project where I was forced to go back to 1488/89's, I
>would remove myself from the project... Given a 5V system, I simply
>could not justify the extra power supply to support the older chips.
>> - Tom
>
I know what the data sheet says, but it came up in conversation, mostly
because
they have other parts that don't go that fast. The story, confirmed in
several different
discussions, was that if their rating said 116k, then some, maybe most,
would work
at that speed, but they couldn't guarantee the fallout. This struck me as
unusual
to say the least, since in my experience, if the spec says 116, then EVERY
part
I get should run just fine at 116.
The extra supplies arent' bad, especially if you're doing a switcher reg
already.
Use a flyback, and add a couple windings, diodes and caps, and you're there.
I usually design to 100k quantities or better, so customs aren't a problem.
:)
>MAX202's are cheaper and don't suffer from the MAX232A 100nF cap lockup
>problems.
Analog Devices' ADM202 (232) is more cheaper then MAX2*2, btw, it is more
cheapest solution - DS14C232 from National Semiconductor.
Of couse all of this is pin-to-pin compatible.
==================================
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