LM5177DCPR.A datasheet(29/60 Pages) TI2

29 / 60 page

IOMON

CONTROL

IMONOUT

From

current sense

IMONP

IMONN

COMP

–

Core

Logic

From

Main Logic

V(REF)

–

Peak Current

Comparator

I-Peak

Clamp

Figure 7-16. Current Monitor Functional Block Diagram

7.3.14 Short Circuit - Hiccup Protection

The LM5177 features a short circuit protection or over current protection. This protection uses cycle-by-cycle

peak current sensor connected to the CSA and CSB-pin. There are two modes for this protection. In hiccup

mode, the controller stops the converter operation after detecting cycle-by-cycle peak current longer as the

hiccup mode on-time. The converter logic initiates a discharge of the soft-start capacitor and the output stays off

until the hiccup mode off-time elapses. Then the logic will exit the hiccup mode and re-start the output with a

normal soft-start sequence were the soft-start capacitor is charged with the internal current source. If the short

or overload persist the hiccup timer starts again after the soft-ramp finishes. If hiccup mode protection is not

enabled, the device will operate in cycle-by-cycle current limiting as long as the overload condition persists.

7.3.15 nFLT Pin and Protections

The open-drain nFLT ouput directly follows the input signals of monitoring features. For instance if the power

good flag triggers because the output voltage is falling below the power good threshold the nFLT pins pulls low.

After a power-cycle of the device or in case the internal failure signal disappears the nFLT pin will go back to

HighZ. The input signals to the nFLT pin are digitally de-glitched. Due to this the maximum reaction time of the

FLT pin is given by td(nFLT-PIN)

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LM5177

SNVSBU4F – JUNE 2022 – REVISED JANUARY 2025

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LM5177DCPR.A Datasheet(PDF) 29 Page - Texas Instruments