IR3823 datasheet(21/41 Pages) IRF

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IR3823

www.irf.com

August 1, 2013

into hiccup mode. PGood will go low and the internal

soft start signal will be pulled low. The converter

goes into hiccup mode with some hiccup blanking

time as shown in Figure 16. The convertor stays in

this mode until the over load or short circuit is

removed. With different SS_Select configurations,

the hiccup blanking time is different. Please refer to

the electrical table for details. The actual DC output

current limit point will be greater than the valley point

by an amount equal to approximately half of peak to

peak inductor ripple current.

LIMIT

OCP







IOCP= DC current limit hiccup point

ILIMIT= Over current limit (Valley of Inductor Current)

∆i= Peak-to-peak inductor ripple current

Figure 16: Timing Diagram for Hiccup OCP

Over current limit is affected by the VCC voltage. For

some single rail operations where Vin is 5V or less,

the OCP limit will de-rated due to the drop of VCC

voltage. Figure 17 and Figure 18 show the over

current limit for two single rail applications with

Vin=PVin=5V and Vin=PVin=VCC=4.5V respectively.

Figure 17:OCP Limit at Vin=PVin=5V using Internal LDO

Figure 18: OCP Limit at Vin=PVin=VCC=4.5V

OVER-VOLTAGE PROTECTION (OVP)

Over-voltage protection in IR3823 is achieved by

comparing FB pin voltage to a pre-set threshold.

OVP threshold is set at 1.2×Vref. When FB pin

voltage exceeds the over voltage threshold, an over

voltage trip signal asserts after 2us (typ.) delay.

Then the high side drive signal HDrv is turned off

immediately, PGood flags low. The sync FET

remains on to discharge the output capacitor. When

the VFB voltage drops below the threshold, the sync

FET turns off to prevent the complete depletion of

the output capacitor. After that, HDrv remains off

until a reset is performed by cycling either Vcc or

Enable. Figure 19 shows the timing diagram for over

voltage

protection.

Please

note

that

OVP

comparator becomes active only when the IR3823 is

enabled.

Figure 19: Timing Diagram for Over Voltage Protection

IR3823 Datasheet(PDF) 21 Page - International Rectifier

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