I need to use a TL497AI to step down 24V DC to 5V DC. Am I interrupting the data sheet (http://www.ti.com/lit/ds/symlink/tl497a.pdf) correctly whereby I can only input between 4.5-12V to be stepped down to between 1.2-11V?

 

Correct, maximum input voltage is 15V, nominal supply is 12V. Why dont you use a Lm2596, 4.5 to 40 V input @3amps...

 

It's for an uni assignment, have to use the TL497AI. So I'll step the 24V down to 12V with a zener diode, then step the 12V down to 5V with the TL497AI. Not sure how this will meet the switching regulator design requirement, but I can't see how it can be done by just suing the TL49AI

 

It's for an uni assignment, have to use the TL497AI. So I'll step the 24V down to 12V with a zener diode, then step the 12V down to 5V with the TL497AI. Not sure how this will meet the switching regulator design requirement, but I can't see how it can be done by just suing the TL49AI

The chip supply is limited to 15V but the switching part can run on up to 30V.
See the top diagram on page 8 of the datasheet.

 

But isn't that diagram just saying to use a voltage regulator to lower the input voltage to 12 volts, that is, 24V into the voltage regulator, 12V into the TL497, then configure the TL497 for a 5V output. So if I do it that way I'm only half using the TL497 to step the 24V down to 5V.

 

But isn't that diagram just saying to use a voltage regulator to lower the input voltage to 12 volts, that is, 24V into the voltage regulator, 12V into the TL497, then configure the TL497 for a 5V output. So if I do it that way I'm only half using the TL497 to step the 24V down to 5V.

The 12V regulator is only feeding the control circuitry on the chip not the power switching circuitry so it only needs to handle the 16mA maximum that the chip needs. Your zener diode has to handle the full output current and is doing more than half the work of getting 24V down to 12V with the TL497 getting it from 12V down to 5V.

 

Well how does this config look?

 

Well how does this config look?
View attachment 134501

What a total waste of time this is, if you just want 5V from 24V, use one buck chip,..LM2596

Don't see the point in dropping 24 to 12, to drop it to 5V, your Uni Prof is barking mad!