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In my application, I need -5v for OP-AMP application. Load on -5V is 200mA.

I have come across various possible ways, as follows:

1) Using TPS5430 as inverting buck boost

TPS5430

We are using TPS5430 in our system, so to avoid new inventory, we will prefer this option.

2) Using negative clamper circuit as described Stack Exchange Query Here, I observed -5V was regulating randomly. I tried with different c33 values (0.1uf,4.4nf), but sometimes it worked fine, but not always. Even after connecting dummy load at 7.5V output as per suggestion on that query, regulation was random.

Can someone tell me, 1st option which I listed above,is it safe for regulation(-5V)?

I am concerned because TPS5430 is buck regulator, not buck-boost?

And also, when similar buck (LM2576) used as inverting buck boost it stated in datasheet that it draws more current at input.

LM2576

Is this applicable to TPS5430 also ( in datasheet of TPS5430, it's not mentioned that it will draw more input current as LM2576, I am concerned because my input current has limitation to source high current since there are many peripherals)

Other than this, is there convenient option to generate -5v?

Thank you in advance.

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So, yes. If you want to generate a negative supply voltage from a positive one, you will need an inverting switch-mode power supply. Both your solutions seem to be an implementation of that.

No one can actually comment on the suitability of any specific circuit unless you state the component values that you're going to use – and as far as I can tell, the above circuit is meant for a high positive input voltage, so you'll probably have to go to the datasheet and look up the right values, anyway. Also, there's literally thousands of SMPS controller ICs - I'd rather go to a couple of manufacturer's websites (TI.com, maximintegrated.com, onsemi.com), and use the selection and design tools there to "click together" a fitting inverting power supply then start of with "I already have this IC, can I make it fit?".

5V is pretty common; it's even possible you'll get a device that integrates everything from controller, to switch, to inductor in a single package. They're typically a little more costly than building your own from the components, but they are tested, and if you need to include the construction and testing time into your system costs, that'll probably be worth it for everything less than a couple hundred systems. The Texas Instruments PTN28000A comes to mind.

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  • \$\begingroup\$ Thanks Marcus, Schematic shown above is for -5V only and also values are same .. only input is 12V DC from SMPS. Is it ok to connect Vo pin to gnd and take -5v from gnd pin of ic. \$\endgroup\$ – Electroholic Jun 19 '16 at 8:09
  • \$\begingroup\$ @Electroholic I've addressed exactly that fact in my answer. I don't understand what you're telling me. It is a circuit from the manufacturer's application note. It will work for the parameters the authors state. It might not work for others. \$\endgroup\$ – Marcus Müller Jun 19 '16 at 8:10
  • \$\begingroup\$ Do you mean 12v is too low to get -5v ? Min Vin is given as 5.5v in datasheet. \$\endgroup\$ – Electroholic Jun 19 '16 at 8:13
  • \$\begingroup\$ It's not my circuit. I didn't design it. I don't know if the inductance and capacitors do well enough with +12V supply. I can only read what's written in the schematic, where it says +15V. \$\endgroup\$ – Marcus Müller Jun 19 '16 at 8:18
  • \$\begingroup\$ The datasheet and/or app notes will, however, tell you what size of components to use and how to calculate that. \$\endgroup\$ – Marcus Müller Jun 19 '16 at 8:19
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Other than this, is there convenient option to generate -5v?

Linear tech have a few options: -

enter image description here enter image description here enter image description here enter image description here enter image description here

Options 3 and 4 are isolating 5V converters and of course it takes no imagination at all to see that these can be wired for -5V.

Try also this page on LT's website.

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