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I am trying to incorporate a LEM LAH 100-P current sensor into a project. It requires a dual polarity voltage supply between +/- 12 and 15 volts. What is the best way to implement it?

Digi-key has an article which references many other application notes. But I don't have knowledge of power electronics which makes adapting them difficult. This application note seems promising but components used are for an output of -3.3 to -5.5 volts (part at digikey and datasheet).

Figure from the application note: enter image description here

What components could be used to create a negative supply of 12 to 15 volts? Any suggestions welcomed.

rur2641
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    Charge pump is probably a good match for your requirement (~10 mA). Did you look at Maxim's other charge pump parts? – The Photon Jan 31 '18 at 01:17
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    Just buy a +/- 12V module such as this: https://www.digikey.com/products/en/power-supplies-board-mount/dc-dc-converters/922?k=&pkeyword=&pv2211=i2&FV=ffe0039a&mnonly=0&ColumnSort=0&page=1&quantity=0&ptm=0&fid=0&pageSize=25 – Jack Creasey Jan 31 '18 at 01:21
  • What input will you provide AC ? DC? Output is only 10mA @+/-15V – Tony Stewart EE75 Jan 31 '18 at 01:38
  • Take a look at ICL7662. Old charge pump chip that works well and still around. – Vince Patron Jan 31 '18 at 01:48
  • The LAH 100-P has a nominal output current of 50 mA. [+/- 15V module](https://www.digikey.com/product-detail/en/cui-inc/PDS1-S24-D15-M-TR/102-3337-6-ND/4841458) has a maximum output current of 33 mA. [ICL7662' datasheet](https://datasheets.maximintegrated.com/en/ds/ICL7662-Si7661.pdf) 's note on using it as an inverter states that at 10 mA the voltage drops to -14.4 volts. – rur2641 Jan 31 '18 at 02:29
  • Some of that 50 mA comes from the transformer. The datasheet seems to say it only draws 10 mA from it's supply. – The Photon Jan 31 '18 at 03:20
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    @VincePatron the ICL7662 switches at an annoyingly audible 10 kHz. Better to use a higher frequency part. – τεκ Jan 31 '18 at 04:48
  • Ok, yeah, I know ICL7662 is old. My point is there's a ton of stuff out there, particularly from Maxim, Intersil, Linear, etc. Up to 50 or may 100 mA is doable with switched cap. Beyond that, use an inductive switcher. Switched cap is easier to design with if you're new. For example LTC3261. – Vince Patron Jan 31 '18 at 05:23
  • The project needs 2 current sensors. to be on the safe side I will go with [XP Power IZ2415S](https://www.digikey.com/product-detail/en/xp-power/IZ2415S/1470-1649-5-ND/4488029). It has the added benefit of being easier to breadboard then LTC3261. – rur2641 Jan 31 '18 at 09:40
  • The datasheet says "current consumption = 10 **+Is** mA". Is goes through the transformer to 0V, but must come from +UC or -UC. You need at least +-60mA per sensor. – Bruce Abbott Jan 31 '18 at 09:44
  • "Off-Topic"?! That seems odd. – Seamus Feb 24 '21 at 23:58

2 Answers2

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An easy solution is to use a 780X DC to DC power converter, you could even mock one up for use on the bench with wire and an iron.

Below is shown for a 5V supply, they also have 12V or 15V that would be the same circuit but different part.

Do not get this confused with a 7805 linear regulator, a 7085 linear regulator will not generate a negative voltage and requires a negative rail. Because DC to DC converters can sink current, they can generate negative voltages.

enter image description here

Just to clear up confusion, this is a DC to DC converter:

enter image description here
Source: https://www.cui.com/product/resource/p7805-s.pdf

Voltage Spike
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As it already has been stated in different comments to the original question, there are different possibilities.

You could use in increasing order of complexity:

  • a DC/DC power supply module (typically a plug and play 'block')
  • a charge pump (essentially a controller IC with capacitors)
  • an inverting switching power supply (essentially a controller IC with inductor)
  • an added winding on an existing AC/DC power supply

Since you ask this question, I would suggest you select the first option. Not the cheapest but it is the most fail safe.

For the first 3 options, you can easily use the selection criteria at the large component distributors (Mouser, Farnell, Digi-Key, RS) and select the appropriate input and output voltage range and output current requirement.

gommer
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