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LDO and DC/DC converters in battery powered system

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leszcz

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5v 2a boost from 3,7v

Hi,
Im designing a microcontroller application with MSP430. It will operate with Li-ion 3.7V battery. The circuit needs 3 voltage stages : 5V, 3V, 2.5V

I thought about LDO with 3.7V to 3V conversion (TPS79730) as main value and then two dc/dc converters 3V/5V and 3V/2.5V

The application must be ultra-low power and i need max 10mA.

Is this a good approach at all ? What do u suggest ?

Thanks in advance
 

ldo 3v low power

The battery voltage declines as its stored power is drained.

Possible to use three dc/dc converters?
 

lm1117 circuit question

ive used the ti TPS715A01DRB for 12v nominal (10v to 20v range) battery max = 80mA for the device.
 

ldo or dc/dc converter

Have you considered a flyback.For just one example heres alink.

Code:
http://www.maxim-ic.com/appnotes.cfm/appnote_number/665
 

3v dc ldo

max0412 :
I cite "In general, you shouldn't undertake the design of a flyback transformer unless you have experience or can afford the time to make a number of iterations" :)
I dont have time and prefer to avoid transformers cause it shall be a portable application.

wall0p:
Thats a good part with low ground current but do u suggest to use 3 of them for each voltage ??? What would be the architecture then ? How can I get 5V output with 3,7V input with LDO ??? Apart from that the noise level is very high.

powersys:
Yes its possible to use 3 dc/dc, but what is the adventage of this approach ? What shall the architecture look like in this case ? The noise level is very important for me as well I must say.
 

In that case maybe something like the LTC3204 Low noise Charge Pump.
Vin range from 1.8V to 4.5V, Io=150Ma. Vo=5V, To generate your 5V. Or whatever’s available that’s comparable.
Code:
[url]https://www.linear.com/pc/downloadDocument.do?navId=H0,C1,C1003,C1039,C1133,P9232,D6578[/url]
For your two other voltages use a dual output LDO like TC1302.
Code:
**broken link removed**
This set- up should give you pretty good efficiency and small parts count.
 

    leszcz

    Points: 2
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Hi,
its a good design max4102, thanks also for finding the parts for me. The thing is only about 200uA current supply. Its a bit to much. As a result I decided to redesign the whole circuit and supply it with 3.3V. In this case I need only one additional 1.75 voltage. It makes the whole thing much simplier and with about 7uA current supply much more efficient.

Thx all
 

Hey the best solution is to use a Boost Converter or a charge pump based design. But a Charge pump design is much simpler to design than a boost converter. Also, you can avoid the inductor. But the flip side is that you would need external caps for the charge pump and the ESR and leakage play a major factor. Boost on the other hand is more efficient and programmability is more easily obtained. For more information try the maxim sites for the charge pump or the boost design fundamentals.

Getting a lower voltage is a piece of cake. Try an LDO.
 

Yes, three individual parts or they have duals or triple outputs available from National or Linear.

The TPS61032PWP is probably too large a part (2A) that can boost from 3V to 5V.
This requires min amount of parts.
 

Have You considered an SP6644 from sipex, it is capable of producing from 2.2V up to 5.5V and as I remeber corectly it is capable of doing it even from 0.88V batery. it has several uA $10^{-6} A$ and I think that exixst in Farnell catalogue. I think that it neades something like one coil, five or so resitors two input capacitors, ant two output capacitors. It is not capable of producing high amperahe, but I think that it could produce up to som 100mA.

Nenad Sakan
 

2 propose

a.)

3V supply : use LM1117-ADJ
2.5V : use LM1117-ADJ

b.)

3V supply : use LM1117-ADJ
2.5V supply : connect a series diode ( e.g 1N4001 ) to 3V and get ~ 2.5V from output. A big capacitor (e.g.220uF ) is needed for decoupling at output.

Roger
 

leszcz said:
Hi,
Im designing a microcontroller application with MSP430. It will operate with Li-ion 3.7V battery. The circuit needs 3 voltage stages : 5V, 3V, 2.5V

I thought about LDO with 3.7V to 3V conversion (TPS79730) as main value and then two dc/dc converters 3V/5V and 3V/2.5V

The application must be ultra-low power and i need max 10mA.

Is this a good approach at all ? What do u suggest ?

Thanks in advance

I suggest using DC/DC converters first and then LDO stabilising for removing the noise.
 

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