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# 6 volts DC to 5 volts DC.

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#### yangxh

##### Member level 5
6vdc regulator with 5.1 v zener

I need to reduce 6 volts DC to 5 volts DC. If there is some existent chips can be used.

lm431 & darlington

You need to consider the current and how much your 6V supply can vary in voltage. 6V from four 1.5V dry batterys will drop below 5.5V when only a small fraction of the available energy has been used.

IanP's suggestion of an LDR is probably better but a shunt regulator is a possibility. They tend to be inefficient.
https://www.fairchildsemi.com/ds/TL/TL431A.pdf

reduce 6 volts to 5 volts

I will suggest a new device made by Zilker

(www.zilkerlabs.com)

You can have various O/P voltage w/o changing the circuit

what about a single DIODE ?

Germanio DIODE (0.2V) + Silicon DIODE (0.7V) = 0.9V

What append whit you on the Desert ?

how bout a resistor and a 5V zener diode...

sp

The MAX1598 low-noise, low-dropout linear regulator
operates from a 2.5V to 6.5V input and delivers up to
200mA.
 200mA Output Current

several problems with LDOs:
- they still have a drop out and thus you can't use the battery input all the way down
- linear regs are inefficient which is a significant issue when using a battery.

I'd look at a switcher based design for much higher efficiency. For example, with the national LM5000, you can get 5V out with 80% efficiency and an input V of 4-6V.

National's web bench will give you a completed design that you can go and build. Just plug in your design criteria.

From 6 to 5 V DC I think the easy solution is 7805 (in TO220 and smaller TO92 package).

It has 3 pins: Vin, GND, Vout (7805 = 5 V)

Bye!

Thelux,

I don't think the 7805 is usable for 6V input since it requires at least 7.2V at the input. This is because 7805 is not a low dropout regulator -- it is a conventional linear regulator using Darlington connected NPNs if I am not mistaken, so the voltage drop is more than 2 Vbe. I think it is actually 2Vbe + Vsat (for PNP driver).

Best regards,
v_c

1} you cannot !! convert 6v dc to 5v using 78 regulators these packages require an overhead of 3.6 v above there ouput rail level to work efficently

best you use a 1n4001 in series to drop .6v each diode
or adding a low value resistor and WORK IT OUT

dont be lazy !!!

and get it right

It's too bad the original poster hasn't responded back. If this is a mains powered device then a LDO regulator with less than 1V DO is the way to go. If it is battery powered, then a swticher like I suggested is the right solution. With out any data it is impossible to know...

Phil

Hi all,

what You say is true but... sometimes things go different from theory.

This is what I measured using one 7805 and good DVM:

In = 5.997 V
Out= from 4.885 to 4.750 V (depending on load)

I think this *MAY* be a solution... depends on load, on 7805 used... without more infos it's the simplest solution to try.

Otherwise resistor, diodes and zener as other people suggested.

Or a DC-DC converter like TMR0511 (RS code 433-8214) with:

Vin = 4.5 to 9
Vout = 5
Iout = 400 mA

Good luck to Yangxh!

Bye.

The 78xx data sheets have charts that show dropout based on load. The problem with taking one measurement is that the parts have a range of dropouts. Also, the point of regulation is to avoid load causing the voltage to fall. Might as well just use a diode to drop the voltage otherwise. The real problem is not the voltage level but the dropout transient which causes all sorts of problems. Dirty power is a recipe for problems.

Generally accepted engineering practice is to give at least 2V headroom for a 78xx Vreg. 6V to 5V is going to be extermely subject to load induced transients.

The DC-DC converter is basically the same as the switch mode design I pointed out. It's a lot cheaper to build your own but the DC-DC is a reasonable way to go if you don't might the cost.

Thank you all.
Though I haven't try anything,I have got much more information from all of you.I think the LDO is a better choice for me.It is very low dropout voltage.

Hello VSMVDD,
I wonder, what's the simulation program u took that snap-shoot from? please tell me.

Thanks,

proteus vsm

Check MinMax, and CDTech, they offer a _very_ wide range of DC-DC converters.

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