FS6500 datasheet(61/153 Pages) NXP

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NXP Semiconductors

FS6500-FS4500-ASILD

Safety power system basis chip with CAN FD and LIN transceivers

FB_CORE

COMP_CORE

FCRBM

VCORE VOLTAGE

L_VCORE

CBOOT_CORE

D_VCORE

RSNUB_VCORE

CSNUB_VCORE

R3b

R4b

GND

PGND

PGND PGND

GND

aaa-037773

ESR CAP.

< 100 mΩ

Figure 44. VCORE buck regulator

12.7.2.2 Light load condition

To improve the converter efficiency and avoid any unwanted output voltage increase, the VCORE voltage

regulator operates in pulse skipping mode during light load conditions. The principle is the same as the VPRE

implementation described in detail in Section 12.7.1.3.

12.7.2.3 Current limitation

A current limitation is implemented to avoid uncontrolled power dissipation inside the device (duty cycle control)

and limits the current below ICORE_LIM. The current limitation is banked when the pass transistor is switched

on during tCORE_BLK_LIM to avoid parasite detection. When the ICORE_LIM threshold is reached, the high-side

integrated MOSFET is switched off. The MOSFET is not switched on again before the next rising edge of the

switching clock.

The current limitation induces a duty cycle reduction and leads to the VCORE output voltage to fall gradually

and may cause an undervoltage condition, bringing the device into a fail-safe state. The current limitation does

not switch off the regulator.

12.7.2.4 Voltage monitoring

The overvoltage detection switches off the regulator. The regulator remains on during an undervoltage

detection. Diagnostic is reported in the dedicated register, generates an interrupt, and may bring the application

into the fail-safe state, depending on the supervisor configuration (register INIT_VCORE_OVUV_IMPACT).

For safety purposes, the FCRBM pin monitors the external resistor bridge (R3/R4) used to set up the final

VCORE voltage through a second resistor bridge (R3b/R4b) to detect an external resistor drift or disconnection.

The monitoring compares the FB_CORE and FCRBM pins (Figure 45) and triggers when FB_CORE – FCRBM

> ±150 mV max.

FS6500-FS4500-ASILD

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

Product data sheet

Rev. 8 — 5 August 2024

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