90V DC-DC converter IC?

[Spehro Pefhany]

There is also the LM5574 - goes up to 75V so you only need to throw
away 15 . I've used it recently.

There's also the LM5009, good for 100V (a bit more on the switch) but
whether it can be used without the zener depends on the spec on that
"90V" including transients etc.



Best regards,
Spehro Pefhany

 

[Terry Given]

So it isn't suitable for starting with shorted loads.

As I said, there is no such thing as 'bad', just more or less appropriate for any given situation.
This circuit is not appropriate for situations where the load may be shorted at startup.

try "where the load may be shorted, ever"

nor is it appropriate when you care about load regulation, line
regulation or efficiency

his current-limited version is even worse. when current limiting into a
short, it turns into a linear regulator......full current, full voltage.

yes there is indeed such a thing as BAD, and this circuit is one
example. Its OK if you are a hobbyist, and really dont care much about
how well your circuit works (Mr Blacks push-in prototype board
construction is a great example) or what the reliability is like;
conversely for a real application, its a disaster.

Cheers
Terry

 

[Mike Harrison]

try "where the load may be shorted, ever"

Fine - there are lots of apps where this will never happen, or if it does you don't care.

nor is it appropriate when you care about load regulation, line
regulation or efficiency

Again, there are many apps where cost is more important than performance.
It was never claimed to be ideal in all circumstances.

I just measured an example I breadboarded last week :
intended to supply around 12V at 100mA

output voltage for an input range of 18 to 33V :

94R load : 12.53 to 12.57
188R load : 12.53 to 12.65V
No load : 12.70 to 12.83

Not as good as most SMPS chips, but more than adequate regulation for many applications.

 

[linnix]

Fine - there are lots of apps where this will never happen, or if it does you don't care.


Again, there are many apps where cost is more important than performance.
It was never claimed to be ideal in all circumstances.

It seems good enough for my 12V to 7V 20mA battery charger.
Furthermore, with the emitter LC tank, it should limit the current
surge and improve oscillations.

By the way, I plan to have three circuits 12V -> 7V, 5V -> 7V and
4V-6V -> 30V sharing a common ferric core. They are only active one
at a time. To save space, there will be six sets of wirings on the
core. A linear rod is the preferred mounting size, but a donut if
necessary. I know circular core is better, but how bad would be a
linear rod. The coils are 20uH to 300uH.

 

[[email protected]]

I am hoping to find a DC-DC converter IC/and or simple circuit that
can take 90VDC and provide 5VDC @ ~ 20 mA. I note that the LT1339CSW
from Linear Tech is a relatively inexpensive surface mount part,
however, input voltages are limited to 60VDC. Can anyone suggest an
alternative, workaround, or confirm that I am barking up the wrong
tree? Thanks.

http://www.linear.com/pc/downloadDocument.do?navId=H0,C1,C1003,C1042,P37694,D25014