Hi guys,

I want to custom intergrate a the LM2596S-3.3 Fixed voltage regulator in my circuit.
Does everything look OK in my circuit, its for powering sensors so the powersupply need to be stable and low noise:


The Capacitors are all Tantalum.

Thanks already!

 

Hi R223,
It should work OK, it is almost identical to the d/s example.
What is the input voltage?
E

 

Hi R223,
It should work OK, it is almost identical to the d/s example.
What is the input voltage?
E

Hello, Eric,
The input voltage is 12VDC from a powersupply

 

Hi R223,
This is a simulation of your circuit.
E

Update:
What is the load current?

 

Will be something like 1A.
How did you simulate my circuit, is there an advance program for that?

 

hi R223,
I am using LTSpice, it is a free download and use simulator.
E.
Link;
https://www.analog.com/en/resources/design-tools-and-calculators/ltspice-simulator.html

This plot shows the power dissipation in LM2596.

 

hi R223,
I am using LTSpice, it is a free download and use simulator.
E.
Link;
https://www.analog.com/en/resources/design-tools-and-calculators/ltspice-simulator.html

This plot shows the power dissipation in LM2596.
View attachment 328495

That doesn't look stable does it?

 

That doesn't look stable does it?

Hi,
Please explain???
E

 

Hi,
Please explain???
E

Yeah, the graph really goes up and down a lot, or I'm a misconcepting it?
I'm not really an expert on this field so let me know if my circuit is stable or not?
It will be hooked up to a 30W 12VDC PSU

 

Hi,
That plot shows the initial inrush of current/wattage at power up.
If you look at the plot after that start up period, the dissipation is approx 190mWatts.

Remember, this is a SMPS LM2596 IC, so there will be switching spikes.

What is the specification of your sensors?
E

 

Hi Eric,

That makes it more clear for me.
The Voltage regulator will be powering a big number of the following sensors: https://www.kiwi-electronics.com/nl...hermokoppel-versterker-max31856-breakout-2719

They run on 3,3V, but I don't know if they can handle the voltage fluctations.
Can my Voltage regulator be improved further? (Btw, my schematic doesn't use a RLOAD).

Thanks already!

 

the powersupply need to be stable and low noise

Switching supplies tend to be noisy.
How "low noise" do you need?
Generally you can filter noise in the signal by using a low-pass filter or signal averaging, depending on how often you want to read the temperature.

Btw, my schematic doesn't use a RLOAD

That simulates the load of your sensors.

 

Switching supplies tend to be noisy.
How "low noise" do you need?
That simulates the load of your sensors.

Yeah that's something I don't really know yet, but lower noise seems better for my temperature sensors.
Are the better options than switching supplies, I read that linear supplies generate a lot of heat?

 

Hi R,
Linear regulators can run hot.
If you used a 3.3Vreg at 1amp from a12V supply, that would 12V-3.3V= 8.7V *1amp = ~9 Watts
E

 

Hi R,
You could consider a LM2596 5V or Adj type, which would drive a LDO 1A 3.3V linear or Iwo???
E

 

lower noise seems better for my temperature sensors.

An added LC low-pass filter at the regulator will help reduce the noise, if needed.

 

Have you identified a problem with noise or are you guessing that there might be?

A temperature sensor will be working at a frequency ridiculously lower than the noise from an SMPS. Problems are more likely when the frequencies are closer to each other. I would expect that the board already has filtering for higher frequencies.

 

Hi R223,
This is a simulation of your circuit.
E

Update:
What is the load current?

View attachment 328494

Sir, may I know what simulation software you used here?

 

Hi 85,
There is a link in post #6.

E

 

Have you identified a problem with noise or are you guessing that there might be?

A temperature sensor will be working at a frequency ridiculously lower than the noise from an SMPS. Problems are more likely when the frequencies are closer to each other. I would expect that the board already has filtering for higher frequencies.

I'm really carefull with the noise and want to minimize as much as possible, in the past I've used the MAX6675 sensor who was even more sensetive for the noise, that was really a big drama so that's why I want to minimize as much as possible.

This is also my building my own complete PLC so I want to make sure I do the right thing.