Can this switched capacitor inverter sink current (LM2687)

[palpurul]

Hello guys,
I was looking for a way to generate negative voltages to supply opamp and I found this nice chip from TI link:http://www.ti.com/product/LM2687. One thing in the datasheet caught my eye is that Vout (negative voltage output) is connected to the N-MOSFET's source (image attached). As I said I'm going to use that chip to bias the opamps's negative supply pin, so it has to sink current. How can it do that with this configuration at the output?

[ogden]

Hello guys,
I was looking for a way to generate negative voltages to supply opamp and I found this nice chip from TI link:http://www.ti.com/product/LM2687. One thing in the datasheet caught my eye is that Vout (negative voltage output) is connected to the N-MOSFET's source (image attached). As I said I'm going to use that chip to bias the opamps's negative supply pin, so it has to sink current. How can it do that with this configuration at the output?

Particular IC is negative voltage inverter with LDO. I don't know what you mean by saying "I'm going to use that chip to bias the opamps's negative supply pin, so it has to sink current", but this IC is ok for negative rail of opamp in case bipolar supply for opamp needed.

[palpurul]

Thanks for your response ogden.

Hello guys,
I was looking for a way to generate negative voltages to supply opamp and I found this nice chip from TI link:http://www.ti.com/product/LM2687. One thing in the datasheet caught my eye is that Vout (negative voltage output) is connected to the N-MOSFET's source (image attached). As I said I'm going to use that chip to bias the opamps's negative supply pin, so it has to sink current. How can it do that with this configuration at the output?

Particular IC is negative voltage inverter with LDO. I don't know what you mean by saying "I'm going to use that chip to bias the opamps's negative supply pin, so it has to sink current", but this IC is ok for negative rail of opamp in case bipolar supply for opamp needed.

Let me clarify. The current must flow into the Vout pin of LM2687 and this pin is connected to the source of the NMOS inside the chip. My understanding is that the current flows from drain to source in NMOS transistors not the other way around. When LM2687 is sinking, current must flow from source to drain. That's what I was trying to say. What am I missing here?

[ogden]

Let me clarify. The current must flow into the Vout pin of LM2687

Current flows *into* output. This is how every negative supply works. No problem here.

My understanding is that the current flows from drain to source in NMOS transistors not the other way around.

Yes you are right and your question is valid. Anyway - If regulator says it is for negative voltage then you shall rely on this information disregarding how mosftet is shown in it's internal circuit illustration which definitely is far from actual circuit. [edit] - Because NMOS you know, may differ from MOS which is used internally in that particular IC. Just accept that it works and proceed further with your project

[palpurul]

Current flows *into* output. This is how every negative supply works. No problem here.

Yea, common sense. The schematic they provided is still confusing.

Thanks for the help!