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6 volts DC to 5 volts DC.

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yangxh

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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.
 

IanP

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throwaway18

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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.
http://www.elexp.com/t_shunt.htm
http://www.fairchildsemi.com/ds/TL/TL431A.pdf
 

calvinhorng

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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
 

unmonje

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what about a single DIODE ?

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

What append whit you on the Desert ? :)
 

ruben852

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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
 

philba

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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.
 

Thelux

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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!
 

v_c

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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
 

VSMVDD

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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

look in google for series load resistor and zener configurations to match your needs

dont be lazy !!!

and get it right

:cry:
 

philba

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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
 

Thelux

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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.
 

philba

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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.
 

yangxh

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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.
 

deb_mallik

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use lm431 zener with low dropout transistor ...download datasheet for lm431 in google.com
 

bamdad

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

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