3.3V to 1.5V Conversion - Technique

[mic5]

This is simple circuit to convert 3.3V into 1.5V with voltage divider at the output. My plan is to use the regulated 1.5V to the circuit.

In case, if any failure in LDO, it should not affect the circuit performance. So, the series diode section is added across the LDO as shown in figure (Suggested by a friend) to supply 1.2V at the output through diodes connection.

Is this idea is acceptable? What kind of problems will come through?

 

[Roff]

If you expect the circuit being powered to work with the LDO essentially out of the circuit, then what's the point of the LDO? In other words, if the load doesn't need regulation, why have it?

 

[mic5]

If you expect the circuit being powered to work with the LDO essentially out of the circuit, then what's the point of the LDO? In other words, if the load doesn't need regulation, why have it?

The load voltage requirement is 1.5V/1.2V. Any how, 3.3V is the regulated supply. It is two way supply to the load for reliability.

 

[Roff]

ES1B-13-F is a 1 Amp diode. If the load is shorted, how much current can the 3.3V supply deliver?

 

[mic5]

ES1B-13-F is a 1 Amp diode. If the load is shorted, how much current can the 3.3V supply deliver?

3.3V can deliver upto 3A. Can I conclude that the diode will affect the load anyway?

 

[Roff]

3.3V can deliver upto 3A. Can I conclude that the diode will affect the load anyway?

My main concern with the diodes is that, if you get a short across the load, at least one diode will probably burn out. If you're going to use this scheme, you should choose diodes rated for at least 5 or 6A continuous current. Do not use Schottkys, as their forward voltage drop is too low.
If the load is very light, the output voltage may be above 1.5V, as the forward drop of a diode varies with current.