# Negative 15V supply from 24Vdc

For my application I have two AD633 Analog Multipliers that need a ground referenced +-15V supply. I have a 24VDC and a 8 VDC supply to use, but i would prefer to use the 24V supply. I've looked at several options, But most used too many components, So am after a solution that uses as few components as possible and will last for a long time.

• you may get a +12/-12 from the 24V then use a boost to 15V each side (positive & negative) – francois P Aug 30 at 22:26
• I cant. I need to maintain the same ground for everything – Bruno Carreira Aug 30 at 22:29
• What does "simple" mean to you? Please tell us what options you have discarded so we don't waste time suggesting them to you. – Elliot Alderson Aug 30 at 22:42
• Hmmm... if you make -Vs=GND and +Vs=24V, then the AD633 will "think" that +12V (half way between -Vs and +Vs) is ground (notice that the AD633 has no GND pin), so you can use it as your virtual ground. So you can shift your input signals up by 12V and shift your output down 12V (if you really need to). – joribama Aug 30 at 22:50
• AD633 has differential inputs, so the input voltage is not ground-referenced. It has an offset pin to set the zero output voltage too. So it does not care about GND. What is important is the input/output voltage range, which is +/-10V and +/-11V resp with +/-15V supplies. So, input voltage range is [5V above neg supply to 5V below pos supply]. You can use any supply voltages you want as long as the input and output voltages you require are within acceptable range. So, please clarify... – peufeu Aug 31 at 12:51

You can use inverting charge pump, buck-boost voltage inverter or a virtual ground op amp based solution to split rails.

This is one example component which can provide $$\-15\,\mathrm{V}\$$. It is a simple dc-to-dc converter module.

Part number: P7805-Q24-S15-S

Do not miss to notice the pin numbering in both configuration.

• The charge pump, i guess is not very stable and with few mA. Virtual groun i cant use because other systems connected to it. Buck boost i dont know, what it is? Can you point me some diagram? – Bruno Carreira Aug 30 at 22:32
• TPS63700 looks like a good solution but its packaging is qfn, and i need pdip. – Bruno Carreira Aug 30 at 22:40
• training.ti.com/… – Umar Aug 30 at 22:41
• ti.com/product/LM2840 is the cheapest one and supports the requirement. – Umar Aug 30 at 22:42
• I think max766 will do the trick for negative voltage. If i had another solution, that provide both -15v and 15v would be perfect – Bruno Carreira Aug 30 at 22:57