RY8310

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30V 1.2A 1.4MHz Synchronous Step-Down Regulator

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Internal Soft-Start

The soft-start is implemented to prevent the converter output voltage from overshooting during startup. When the

chip starts, the internal circuitry generates a soft-start voltage (SS) ramping up from 0V to 0.8V. When it is lower

than the internal reference (REF), SS overrides REF so the error amplifier uses SS as the reference. When SS is

higher than REF, REF regains control. The SS time is internally max to 1ms.

Over Current Protection and Hiccup

The RY8310 has cycle-by-cycle over current limit when the inductor current peak value exceeds the set current

limit threshold. Meanwhile, output voltage starts to drop until FB is below the Under-Voltage (UV) threshold. Once

a UV is triggered, the RY8310 enters hiccup mode to periodically restart the part. This protection mode is especially

useful when the output is dead-short to ground. The average short circuit current is greatly reduced to alleviate the

thermal issue and to protect the regulator. The RY8310 exits the hiccup mode once the over current condition is

removed.

Startup and Shutdown

If both VIN and EN are higher than their appropriate thresholds, the chip starts. The reference block starts first,

generating stable reference voltage and currents, and then the internal regulator is enabled. The regulator provides

stable supply for the remaining circuitries. Three events can shut down the chip: EN low, VIN low and thermal

shutdown. In the shutdown procedure, the signaling path is first blocked to avoid any fault triggering. The comp

voltage and the internal supply rail are then pulled down. The floating driver is not subject to this shutdown

command.