As an ripple current rating engineer, I am frequently asked about operating regulators with no load. Most modern LDOs and switching regulators are stable with no load, so why do people repeatedly ask?
Most newer devices are designed to operate with no load, and exceptions to this rule are very limited. The ADP1740 and other low-voltage, high-current LDOs fall into this category. What if the data sheet doesn’t explicitly specify a minimum load? In most cases, a minimum load is not required. As shown in Figure E, the ADP2370 high-voltage, low-quiescent-current buck regulator produces increased ripple due to PSM operation when the load switches between 800 mA and 1 mA. The fact that the test was done at 1 mA does not indicate that 1 mA is the minimum load. ADP2370 load transient in power-saving mode.
Figure F shows the ripple voltage changing with load current. Conclusion Most modern regulators are stable with zero load current, but when in doubt, consult the data sheet. Analog Dialogue, Volume 41, Number 2, 2007. Luca Vassalli has been with Analog Devices for over 12 years in a variety of roles. He has been involved with the support and design of many analog systems, including optical communication, wireless systems, medical diagnostics equipment, and test equipment.