LM5145 datasheet(42/73 Pages) TI2

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(31)

8.2.1.2.4 Shunt Resistors

1. Calculate the shunt resistance based on a maximum peak current capability at least 20% higher than the

peak inductor current at full load to provide sufficient margin during start-up and load-step transients. Use

Equation 32 to calculate the shunt resistances.

(32)

where

• VCS(th) is the 60mV current limit threshold.

2. Select a standard resistance value of 2mΩ for both shunts. A 1225 footprint component with wide aspect

ratio termination design provides a 3W power rating, parasitic inductance (ESL) less than 1nH, and compact

PCB layout. Carefully adhere to the layout guidelines in Layout Guidelines to make sure that noise and

DC errors do not corrupt the current-sense voltages measured differentially at the [ISNS1+, VOUT1] and

[ISNS2+, VOUT2] pins.

3. Place the shunt resistor close to the inductor.

4. Use Kelvin sense connections and route the sense lines differentially from the shunt to the applicable pins of

the LM25137.

5. The current-sense-to-output propagation delay (related to the current limit comparator, internal logic and

power MOSFET gate drivers) causes the peak current to increase above the calculated current limit

threshold. For a total propagation delay of tCS-DELAY of 70ns, use Equation 33 to calculate the worst-case

peak inductor current with the output shorted.

(33)

6. Based on this result, select an inductor for each channel with saturation current greater than 33A across the

full operating temperature range.

8.2.1.2.5 Ceramic Output Capacitors

1. Use Equation 34 to estimate the output capacitance required to manage the output voltage overshoot during

a load-off transient of 10A, assuming a load transient deviation specification of 100mV.

(34)

2. Noting the voltage coefficient of ceramic capacitors where the effective capacitance decreases significantly

with applied voltage, select four 47µF, 10V, X7R, 1210 ceramic output capacitors for each channel.

LM25137

SNVSCU4 – OCTOBER 2025

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LM5145 Datasheet(PDF) 42 Page - Texas Instruments