LM5145 datasheet(25/73 Pages) TI2

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7.3.11 Inductor Current Sense (ISNS1+, BIAS1/VOUT1, ISNS2+, VOUT2)

There are two methods to sense the inductor current of the buck power stage. The first uses a current sense

resistor (also known as a shunt) in series with the inductor, and the second avails of the DC resistance of the

inductor (DCR current sensing).

7.3.11.1 Shunt Current Sensing

Figure 7-5 illustrates inductor current sensing using a shunt resistor. This configuration continuously monitors

the inductor current to provide accurate overcurrent protection across the operating temperature range. For

optimal current sense accuracy and overcurrent protection, use a low parasitic inductance shunt resistor of ±1%

tolerance connected between the inductor and the output. Use Kelvin sense connections at the shunt and route

the sense lines differentially back to the LM25137.

If the peak voltage sensed differentially at [ISNS1+, BIAS1/VOUT1] or [ISNS2+, VOUT2] exceeds the current

limit threshold of 60mV, the current limit comparator immediately terminates the respective HO output for

cycle-by-cycle current limiting. Calculate the shunt resistance using Equation 6.

CS-TH

OUT(CL)

(6)

where

• VCS-TH is current sense threshold of 60mV.

• IOUT(CL) is the overcurrent setpoint that is set higher than the maximum load current to avoid tripping the

overcurrent comparator during load transients.

• ΔIL is the peak-to-peak inductor ripple current.

VOUT1

BIAS1/VOUT1

Current sense

amplifier

COUT1

ISNS1+

LO1

RS1

VIN

CS gain = 10

Figure 7-5. Shunt Current Sensing Implementation

7.3.11.2 Inductor DCR Current Sensing

For high-power applications that do not require accurate current-limit protection, inductor DCR current sensing

is preferable. This technique provides lossless and continuous monitoring of the inductor current using an RC

sense network in parallel with the inductor. Select an inductor with a low DCR tolerance to achieve a typical

current limit accuracy within the range of 10% to 15% at room temperature. Components RCS and CCS in Figure

7-6 create a low-pass filter across the inductor to enable differential sensing of the voltage drop across the

inductor DCR.

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LM25137

SNVSCU4 – OCTOBER 2025

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