LM5177 datasheet(40/112 Pages) TI

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V(SW2)

C(O2)

C(O1)

ISNSP

ISNSN

ILIMCOMP

C(ILIMCOMP)

R(LOAD)

R(CS)

Figure 8-21. Simplified Schematic current limit components with resistive load

For a electronic load (CC-mode CR-mode) a type II compensation network might be necessary to adopt to the

internal regulation loop and bandwidth of the used electronic load. Please refer to the Quick Start Calculator Tool

for more detailed optimization.

If the current limit threshold is selected by a resistor instead of the internal DAC the regulation overwrites the

voltage loop once V(ISET) is increasing to the threshold voltage (typ. 1V). The threshold voltage for ISET can be

calculated with:

VISET = VISNSP −VISNSN ∙gmILIMCOMP ∙RISET

(23)

Hence the resistor value to select the current limit threshold voltage calculates with:

RISET =

VISET

VISNSP − VISNSN ∙gmILIMCOMP

(24)

For high frequency noise suppression a capacitor based on the following equation should be placed in parallel to

R(ISET)

CISET = 1

π∙ fSW ∙RISET

(25)

The read-out register value of the ''ILIM_THRESHOLD" control register is clamped for the lower and for the

upper limit of the register range.

• The reg. readout value is clamped to the lowest clamp current ( e.g. 500mA) if a register value below the

value of clamp current been written in before.

• The reg. readout value is clamped to the highest clamp current if a register value above the highest value of

clamp current has been written in before.

8.3.11.3 Output Current Monitor

The current through the sense resistor can be monitored by the CDC pin simultaneously and has no impact to

a configured current limit via the ILIMCOMP pin. If the limiter is disabled (IMON_LIMITER_EN = 0b0) both pins

provide a proportional current to the differential voltage of ISNSP/N with. The Voltage can be calculated with

VCDC = VISNSP −VISNSN ×gmCDC ×RCDC

(26)

VILIMCOMP = VISNSP −VISNSN ×gmILIMCOMP ×RILIMCOMP

(27)

LM251772

SNVSCT9 – OCTOBER 2024

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