MFS5600AMBA0ES datasheet(22/111 Pages) NXP

22 / 111 page

NXP Semiconductors

FS5600

Automotive buck regulator and controller with voltage monitors and watchdog timer

12.2.1.2.1 Using current sense resistor

For low and medium output currents ( < 8 A), current sense can be done using a shunt

resistor Rshunt in series with the SW2 inductor LSW2, as shown in Figure 9 below.

aaa-041308

Rshunt

10 m

Lsw2

4.7 H

0.1 F

22 F

SWIN

10 F

CONTROL,

DRIVER

AND

LOGIC

SW2BOOT

VCC

SW2CSP

SW2FB

SW2GHS

EN2

SW2GLS

SW2LX

SW2CSN

Figure 9. SW2 application schematic with Rshunt current sensing

The power dissipation on PRSHUNT = ISW22 * Rshunt. For example, when ISW2 = 5.0 A

and Rshunt = 0.01 Ω, PRSHUNT is 0.25 W.

The SW2 current limitation is calculated as OTP_SW2_ILIM divided by the Rshunt. For

example, for OTP_SW2_ILIM = 80 mV and Rshunt = 0.01 Ω, the peak current limit is 8.0

12.2.1.2.2 Inductor DCR current sense

For high current applications (ISW2 > 8.0 A), the power dissipation in the current

sense resistor becomes non-negligible (> 0.6 W). In that case, the DCR current sense

technique can be a good alternative, using the intrinsic DCR of the inductor to sense the

current. However, the inductor DCR value is less accurate than a shunt resistor, which

impacts the current limit accuracy. A higher resistance value means a lower current

limitation, and less accuracy means a wider current limitation range.

Figure 10. DCR current sense with a single capacitor

aaa-041309

RDCR

LSW2

0.047 F

22 F

SWIN

10 F

CONTROL,

DRIVER

AND

LOGIC

SW2BOOT

VCC

SW2CSP

SW2FB

SW2GHS

EN2

SW2GLS

SW2LX

SW2CSN

FS5600

All information provided in this document is subject to legal disclaimers.

Product data sheet

Rev. 3 — 2 August 2022

22 / 111

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