FS6407 datasheet(48/111 Pages) NXP

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NXP Semiconductors

FS6407/FS6408

6.7.1.5

VPRE voltage monitoring

The overvoltage detection switches OFF the regulator. The undervoltage detector is disabled when the regulator is switched OFF

reporting an undervoltage. Diagnostic is reported in the dedicated register and generate an Interrupt.

The undervoltage detection does not switches OFF the regulator. However, VPRE decrease may induce an undervoltage on a regulator

attached to VPRE (VCORE, VCCA, VAUX, or CAN_5V), and bring the application in Fail-safe state depending on the supervisor

configuration (registers INIT SUPERVISOR 1, 2, 3).

6.7.1.6

VPRE efficiency

VPRE efficiency versus current load is given for information based on typical external component criteria described in the table close to

the graph and at three different VSUP voltages (24 V, 32 V, and 36 V) covering typical industrial operating range. The efficiency is valid in

Buck mode only and above 200 mA load on VPRE to be in continuous mode in the 22 µH inductor. The efficiency is calculated and has

to be verified by measurement at application level.

Figure 32. VPRE efficiency

6.7.2

VCORE voltage regulator

This voltage regulator is a step-down DC-DC converter operating in Voltage Control mode. The high-side switching MOSFET is integrated

in the device and the PWM frequency is fixed at 2.4 MHz typical. The output voltage is configurable from 1.2 V to 3.3 V range and

adjustable around these voltages with an external resistor divider (R3/R4) connected between VCORE and the feedback pin (FB_CORE)

(Figure 33).

VCORE = VCORE_FB x ((R3 + R4) / R4)

The voltage accuracy is

±2.0% (without the external resistor bridge R3/R4 accuracy) and the max output current is 1.5 A. The stability of

the overall converter is done by an external compensation network (R1/C1/R2/C2) connected to the pin COMP_CORE. It is recommended

to use 1.0% accuracy resistors and set R4 = 8.06 k

Ω and adjust R3 to obtain the final VCORE voltage needed for the MCU core supply.

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