Maxim has announced 40V load dump-tolerant dc-dc buck chips that “in peak current mode draw the industry’s lowest Iq, just 3.5µA in the low-power operating mode”, claimed the firm, “which is key to meeting OEM Iq consumption requirements of 100µA per module.” That said, this product page says “3.5µA quiescent current when in stand-by mode” …
This story continues at Always-on automotive PSU chip draws 3.5µA quiescent
Or just read more coverage at Electronics Weekly