# Cost-Effective CPLD micropower 1.8V from regulated 3.3V

in my design a ispMACH 4032ZE CPLD (32Macrocells) operates as SPI slave driven by a moderate 8MHz master-clock. The part requires a 1.8V core supply drawing (estimated) tiny 100uA over the full temperature range according to the data sheet.

A well regulated 3.3V supply which is derived from the 6V...8.4V board supply via an LDO is available on the board. Since the CPLD is the only 1.8V part on the board a full-blown LDO regulator seems overkill and I wonder whether there are more cost- and/or space efficient solutions.

The board supply range of 6V...8.4V seemingly rules out most affordable dual output LDO regulators, even 1.8V zener diodes are similarly priced. (0.3€)

The most cost effective solution seems to be a resistor divider (1.8k/1.5) plus capacitor... however this seems somewhat wrong for a power rail.

Remark

I recognize that there are cheap LDOs that would easily satisfy my requirements and which I probably will use for the sake of predictability and robustness. Still, my question aimed at the slightly uncommon solutions such as using LEDs for voltage dropping.

Many thanks!

• A 0.3€ zener diode as a regulator is too expensive ? A voltage divider may not fit the CPLD power requirements. Have you take a look at Linear LT3008/LT3009 (tiny LDOs but maybe a bit expensive for you) ? – zeqL Dec 5 '13 at 16:20
• LDO's are available with budgetary pricing (qty 1000) down to $0.12 at least (so figure maybe$0.50 or \$0.60 in small lots). A zener might be slightly cheaper, but also fussier to design with. – The Photon Dec 5 '13 at 17:28