High voltage line drivers

[David]

Can someone suggest a high voltage line driver IC? I have requirements
for two seperate uses.

1.) High voltage input. The IC needs to receive 0-30V digital input
voltages and output 5V logic levels. However, I still want the driver
to work if the input voltage levels are only 0-3.3V.

2.) High voltage output. The IC needs to receive 5V digital input
voltages and output 30V digital equivilents.

Thanks,
David

 

[mkaras]

Can someone suggest a high voltage line driver IC? I have requirements
for two seperate uses.

1.) High voltage input. The IC needs to receive 0-30V digital input
voltages and output 5V logic levels. However, I still want the driver
to work if the input voltage levels are only 0-3.3V.

2.) High voltage output. The IC needs to receive 5V digital input
voltages and output 30V digital equivilents.

Thanks,
David

For the 1) application get your hands on the old style RS232 receiver
of the 1488/1489 set. The DS1489s inputs work up to +/- 30V.

For the 2) driver take a look at the SN75452 type parts. These can
handle up to 30V on the outputs. (Both Digikey and Jameco have them in
stock).

These are older parts so I would encourage you to look at other lower
voltage transmission techniques if you are intending to go into
production with the thing you are trying to design/build.

- mkaras

 

[Ancient_Hacker]

Can someone suggest a high voltage line driver IC? I have requirements
for two seperate uses.

1.) High voltage input. The IC needs to receive 0-30V digital input
voltages and output 5V logic levels. However, I still want the driver
to work if the input voltage levels are only 0-3.3V.

Do you need the receiver to automatically center its threshold right in
the middle?

2.) High voltage output. The IC needs to receive 5V digital input
voltages and output 30V digital equivilents.

How far does the signal have to go? At what data rate? Does it have
to be short-circuit protected? What about static protection?



Your basic LM339 comparator IIRC can be used for both jobs if the
requirements arent too tough.

 

[David]

For the 1) application get your hands on the old style RS232 receiver
of the 1488/1489 set. The DS1489s inputs work up to +/- 30V.

Interesting idea. I'll have to investigate.

For the 2) driver take a look at the SN75452 type parts. These can
handle up to 30V on the outputs. (Both Digikey and Jameco have them in
stock).

I've thought about open collector solutions, but I was hoping for push
pull.

These are older parts so I would encourage you to look at other lower
voltage transmission techniques if you are intending to go into
production with the thing you are trying to design/build.

I do intend to enter production. It is an industrial control application
that needs to interface with PLC's. I'm no PLC expert, but I believe
they typically have 24V digital I/O. That is why I need the high
voltage.

However, I also want the device to be usefull on a lab bench where 3.3V
logic is prominent. That is why I need the large range of logic
voltages.

Thanks,
David

 

[David]

Do you need the receiver to automatically center its threshold right in
the middle?

This would be a great feature, but not absolutely required. It would be
acceptable for the vIL_MAX and vIH_MIN to remain constant as long as
they worked from 3.3V logic all the way up to 24V logic.

How far does the signal have to go? At what data rate? Does it have
to be short-circuit protected? What about static protection?

This is an industrial control product that will interface to PLC's which
typically operate at 24V. The transmission distance can become very
long. Data rates will be slow. Maybe 100ns to 200ns risetimes. Short
circuit protection is very desireable as well as at least 2KV static
protection.

Your basic LM339 comparator IIRC can be used for both jobs if the
requirements arent too tough.

That is a very good suggestion. That may be exactly what what I need.
What is a typical switching time for a comparator that is saturated at
the rail?


Thanks,
David

 

[JoeBloe]

Can someone suggest a high voltage line driver IC? I have requirements
for two seperate uses.

1.) High voltage input. The IC needs to receive 0-30V digital input
voltages and output 5V logic levels. However, I still want the driver
to work if the input voltage levels are only 0-3.3V.

2.) High voltage output. The IC needs to receive 5V digital input
voltages and output 30V digital equivilents.

Thanks,
David

There is at least one problem with what you need. To rise to 30
Volts can be said to be easy. To do so with digital data, a factor
known as slew rate weighs in. You won't be able to go very fast
before the slew rate issues corrupt the data, limiting the rate you
can pass data at. Are such chips even around?

It is sort of akin to "floating" ones valves out from revving an
engine to high for the weak valve springs. Motor can only turn so
fast.

 

[Ancient_Hacker]

This would be a great feature, but not absolutely required. It would be
acceptable for the vIL_MAX and vIH_MIN to remain constant as long as
they worked from 3.3V logic all the way up to 24V logic.




This is an industrial control product that will interface to PLC's which
typically operate at 24V. The transmission distance can become very
long. Data rates will be slow. Maybe 100ns to 200ns risetimes. Short
circuit protection is very desireable as well as at least 2KV static
protection.

Whoa, Nelly! Sending 100nsec risetime signals any distance is going
to require using differential twisted-pair or coax. For the
twisted-pair you'll need some strong differential drivers, for the coax
some 50 or 75 ohm drivers. The wire type you choose will determine the
exact driver you'll need. See the "interface" section of IC's at
www.national.com or www.ti.com

That is a very good suggestion. That may be exactly what what I need.
What is a typical switching time for a comparator that is saturated at
the rail?

Well the 339 can do 30 volts output, OR 50 ohms, but not both at once.