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How to isolate and wire?

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neko_whisker

New Member
Hi all,
I am having a knotty problem as to how to wire and isolate pins from pther pins.

Take a look at this pic below, I have drew up.
**broken link removed**

I have momentary switches S0, S1 ,S2 and S3.
And there are diodes to isolate any switches from other input pins if any one of them is switched on. Only specified switch is tunrned on for its own input pin. The reason why I used this method is to conserve power while lenthening the battery life.

The diagram looks okay except, I cannot think of way to isolate S0 from other SX when shdn is used to shut down power when it is shorted to ground while shdn is switced to 1.2V to wake up. I cannot think of a way to isolate 1.2V from ground. (See the dashed lines)

Your help will be appreciated.
Thanks in advance.
clement
 

Hero999

Banned
The diodes all have a loss of at least 0.6V so you won't have much left unless you use germanium or Schottky; what good is 0.6V?

I don't understand your question, build it on a PCB and it should work providing you can actually do something with your pathetic 0.6V
 

ericgibbs

Well-Known Member
Most Helpful Member
hi Clement,
Can you post the rest of the circuit?, there maybe easier ways to get the result you want..

What are the 4 output pins switching?

Like to help, but cannot see what you are trying to do with the actual circuit.
 

neko_whisker

New Member
Hi Hero999 and ericgibbs,
Here's the pic. I am using it for tranmission project.
I am using RF600E and RTFQ1.
You can see some notes I have written.

**broken link removed**

Would appreciate your help.
Clement
 

Roff

Well-Known Member
That doesn't look right to me. For starters, what is LT3525-3.3? I can't find a datasheet for it.
EDIT: I guess you meant LTC3525-3.3.
 
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ericgibbs

Well-Known Member
Most Helpful Member
hi,
Have a look at this change for the select switches.
 
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neko_whisker

New Member
Hi Eric Thank you very much for your help.
What a brillant idea! Wow. I never thought of that!
Now just want to add some wires in order to power up LTC3525-3.3. (Hi, Roff, you are right, My apologies), after shutdown.

**broken link removed**

Thanks again I will look into jumides' comment even though it has worked before with receiver.

Thanks all.
 

ericgibbs

Well-Known Member
Most Helpful Member
hi neko,
If your switch contacts are suitable, why dont you use the linking to connect the battery to the LTC..?? no diodes!! and the /shtdwn always enabled??:)
 
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Roff

Well-Known Member
1.2V is not a valid logic level for the RF600E. See the table below, which was excerpted from the datasheet. You need to use VCC (+3.3V, in this instance) for your switch levels.
 

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neko_whisker

New Member
Hi Eric, I have built it before I made changes. The reason? I find that the battery is used up in just 2 or 3 days. That's because if the 1.2V(from battery) is taken away from shdn pin and is left disconnected, it is still active and floating somewhere in the range. So either shdn pin is connected to above 1v or 0V, it will be in active or shutdown mode respecively. That is, I want to enable or disenable LTC3525-3.3 by any switches, to conserve battery's power. You may refer to datasheet. And I am surprised that 10uH inductor is connected to shdn pin in your drawing. How is it possible? see page 7 of this datasheet.
Roff, I am aware. But I connected 1.2V to SO via diode and it still works. If not, how do we isolate S0 from other switches, if we want to enable and disenable LTC3525-3.3?
Please advise. Thanks in advance
 

ericgibbs

Well-Known Member
Most Helpful Member
neko_whisker said:
Hi Eric, I have built it before I made changes. The reason? I find that the battery is used up in just 2 or 3 days. That's because if the 1.2V(from battery) is taken away from shdn pin and is left disconnected, it is still active and floating somewhere in the range. So either shdn pin is connected to above 1v or 0V, it will be in active or shutdown mode respecively. That is, I want to enable or disenable LTC3525-3.3 by any switches, to conserve battery's power. You may refer to datasheet. And I am surprised that 10uH inductor is connected to shdn pin in your drawing. How is it possible? see page 7 of this datasheet.
Roff, I am aware. But I connected 1.2V to SO via diode and it still works. If not, how do we isolate S0 from other switches, if we want to enable and disenable LTC3525-3.3?
Please advise. Thanks in advance

hi neko,
The idea in the last drawing, is that the push buttons that are wired in series, have one end connected to the 1.2Vbty and the other end connected to the LTC.
So without a PB pressed the LTC is not powered up, pressing any PB puts power on the LTC and of course you want the /shtdwn to be disabled[high].

Also note what Roff is saying about the RF600 logic levels, you could rewire so that these are connected to the LTC Vout.

Do you follow this OK?:)

EDITED: the /shtdwn is connected to Vin of the LTC and the 10uH, which connected to the 1Vbty when a PB is pressed
 
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