LM5145 datasheet(22/70 Pages) TI

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VOUT

Current sense

amplifier

ISNS+

VIN

CS gain = 10

Figure 8-4. Shunt Current Sensing Implementation

The soft-start voltage is clamped 150 mV above FB during an overcurrent condition. Sixteen overcurrent events

must occur before the SS clamp is enabled. This ensures that SS can be pulled low during brief overcurrent

events, preventing output voltage overshoot during recovery.

8.3.12.2 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

8-5 create a low-pass filter across the inductor to enable differential sensing of the voltage across the inductor

DCR.

VOUT1

VOUT

Current sense

amplifier

ISNS+

VIN

CS gain = 10

RCS

CCS

Figure 8-5. Inductor DCR Current Sensing Implementation

The voltage drop across the sense capacitor in the s-domain is given by Equation 11. When the RCSCCS time

constant is equal to LO/RDCR, the voltage developed across the sense capacitor, CCS, is a replica of the inductor

DCR voltage and accurate current sensing is achieved. If the RCSCCS time constant is not equal to the LO/RDCR

time constant, there is a sensing error as follows:

• RCSCCS > LO/RDCR → the DC level is correct, but the AC amplitude is attenuated.

• RCSCCS < LO/RDCR → the DC level is correct, but the AC amplitude is amplified.

LM5148

SNVSC01 – FEBRUARY 2023

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LM5145 Datasheet(PDF) 22 Page - Texas Instruments