LM5145 datasheet(25/69 Pages) TI

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9.3.13 Slope Compensation

The LM25143 provides internal slope compensation for stable operation with peak current-mode control and a

duty cycle greater than 50%. Use Equation 10 to calculate the buck inductance to provide a slope compensation

contribution equal to one times the inductor downslope.

OUT

O-IDEAL

(V) R (m )

( +

24 F

(MHz)

(10)

• A lower inductance value generally increases the peak-to-peak inductor current, which minimizes size and

cost, and improves transient response at the cost of reduced light-load efficiency due to higher cores losses

and peak currents.

• A higher inductance value generally decreases the peak-to-peak inductor current, which increases the full-

load efficiency by reducing switch peak and RMS currents at the cost of requiring larger output capacitors to

meet load-transient specifications.

9.3.14 Inductor Current Sense (CS1, VOUT1, CS2, 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).

9.3.14.1 Shunt Current Sensing

Figure 9-4 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 inductance ±1% tolerance shunt resistor between

the inductor and the output, with a Kelvin connection to the LM25143 current sense amplifier.

If the peak differential current signal sensed from CS to VOUT exceeds the current limit threshold of 73 mV, the

current limit comparator immediately terminates the applicable HO output for cycle-by-cycle current limiting. Use

Equation 11 to calculate the shunt resistance.

OUT(CL)

(11)

where

• VCS is current sense threshold of 73 mV.

• 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.

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LM25143

SNVSC10 – MARCH 2022

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LM5145 Datasheet(PDF) 25 Page - Texas Instruments