High Efficiency Adjustable Supply with LT3088 and LT3680 (or other buck regulator)

Question

Hello, 
 I willing to imlement PSU with buck converter with LT3088 LDO and looking at example in datasheet p26 I see one portion of circuit which is of unclear function. Could someone explain what it does and how it works?

ACaldejon · Accepted Answer

That part makes a negative voltage rail that allows the LT3088 output adjustment to go all the way down to 0V.
The LT3088 has a minimum load of around 2mA, so the LT3088’s output will never go to 0V unless there is a pull-down to a negative voltage.

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High Efficiency Adjustable Supply with LT3088 and LT3680 (or other buck regulator)

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