Seamless LDO boosts battery life with low current at no load

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By Nick Flaherty

Electronics designers often struggle with the question which LDO type to select for the circuit; one option is an LDO with low current consumption but the performance like ripple rejection and transient response speed are often not impressive. Another option is a high performance LDO but these have a high level of internal current consumption even when the output current demand is low.

The RP122 uses Ricoh’s ‘Seamless’ technology to combine both LDO types and offers 90 dB ripple rejection from a 1.7 V to 5.25 V input, fast transient response speed and 9.5 µA current consumption without output load. It also it has a very low noise level at the output voltage of  8 µVrms.

These features are especially of an advantage for battery powered devices with noise sensitive circuits such as smartphones, tablets, digital cameras, RF modules, AD and DA converters. The RP122 contributes to lower the total supply current of the device and increases the lifetime of the battery, and it also eliminates the need to switch between operating modes since the LDO adapts seamlessly to the output current demand.

A number of protection circuits are integrated, a fold-back current limit circuit decreases the output current to approximately 70 mA in case of a short circuit, protecting the LDO and other electronic parts of the application for damage. The thermal protection shuts the LDO down when the junction temperature increases above 165°C. An inrush current limit circuit prevents any output overshoot and undershoot during the start-up period. The inrush period is internally fixed has a maximum of around 700 µs.

The RP122 has an optional auto-discharge function that rapidly discharges the output capacitor once the chip is set to the standby mode. As for a stable operation small ceramic capacitors with a low ESR value and a minimum of 1.0µF can be used. It is available in a 1.0 x 1.0 mm DFN(PLP)1010-4 and 0.64 x 0.64 mm WLCSP-4- P8 package.


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