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Jellybean dual output DC DC converters?
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PartialDischarge:

--- Quote from: spec on November 28, 2018, 11:47:40 pm ---The AP3012 has only got a current sink output so it can't be used easily with a choke to generate a negative supply rail. A 1:1 choke would be required and a bit of jiggery pokey with the feedback, but it still looks doable.

Another approach maybe be to use an external PMOSFET.

--- End quote ---

The schematic goes like this, only 2 more diodes and 2 caps are needed,
http://www.seekic.com/circuit_diagram/Power_Supply_Circuit/POSITIVE_AND_NEGATIVE_VOLTAGE_SWITCHING_SUPPLY.html
spec:

--- Quote from: MasterTech on November 29, 2018, 06:58:28 am ---
--- Quote from: spec on November 28, 2018, 11:47:40 pm ---The AP3012 has only got a current sink output so it can't be used easily with a choke to generate a negative supply rail. A 1:1 choke would be required and a bit of jiggery pokey with the feedback, but it still looks doable.

Another approach maybe be to use an external PMOSFET.

--- End quote ---

The schematic goes like this, only 2 more diodes and 2 caps are needed,
http://www.seekic.com/circuit_diagram/Power_Supply_Circuit/POSITIVE_AND_NEGATIVE_VOLTAGE_SWITCHING_SUPPLY.html

--- End quote ---
Nice find
Shame the LT1170 (5A)(£10.22UK), LT1171 (2A5)(£8.54UK), LT1172 (1A25)(£4.52UK) are quite so expensive, as AD (LT) components normally are.

https://www.analog.com/media/en/technical-documentation/data-sheets/117012fi.pdf

Do you recon that the architecture of the ebay +- output rail module is the same? It would make sense because the seller implies that the magnitude of the negative supply rail is one diode drop less than the magnitude of the positive supply rail, which I think is the same for the LT1172 circuit? I would guess that D1 (1N4148) is used instead of a 1N5819 Schottky diode, as used elsewhere, to try to make the magnitude of the +- supply  rails closer.

If that is the case, it makes the ebay module more attractive than if it used a charge pump for the negative supply rail.
spec:
Just been looking at another of SiliconWizard's chips.  The swinging capacitor LTC3260 looks useful, with built-in +&- LDO regulators giving 50mA. It is low-noise too.

https://www.analog.com/media/en/technical-documentation/data-sheets/3260fa.pdf
PartialDischarge:

--- Quote from: spec on November 29, 2018, 10:21:25 am ---Just been looking at another of SiliconWizard's chips.  The swinging capacitor LTC3260 looks useful, with built-in +&- LDO regulators giving 50mA. It is low-noise too.

https://www.analog.com/media/en/technical-documentation/data-sheets/3260fa.pdf

--- End quote ---
It is a very good solution , it just needs a boost from 3V to 15V if using 2 AA batteries
spec:

--- Quote from: MasterTech on November 29, 2018, 10:27:06 am ---
--- Quote from: spec on November 29, 2018, 10:21:25 am ---Just been looking at another of SiliconWizard's chips.  The swinging capacitor LTC3260 looks useful, with built-in +&- LDO regulators giving 50mA. It is low-noise too.

https://www.analog.com/media/en/technical-documentation/data-sheets/3260fa.pdf

--- End quote ---
It is a very good solution , it just needs a boost from 3V to 15V if using 2 AA batteries

--- End quote ---

Let us know how it performs- I would be very interested. :)
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