FS26 datasheet(112/156 Pages) NXP

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NXP Semiconductors

FS26

Safety system basis chip with low power for ASIL D/ASIL B

19.1.2 Phase shifting

The clocks of the switching regulators VPRE, VCORE, and VBST can be delayed to keep all the regulators from

turning ON at once. This can reduce peak current and improve EMC performance. Each regulator's clock can

be shifted from 1 to 3 clock cycles of the high-frequency clock (configurable by OTP).

aaa-045519

55 ns

18 MHz Clock

CLK1 = 2.25 MHz

CLK2 = 450 kHz

55 ns

Figure 35. Clock phase shifting examples

19.1.3 Spread spectrum

The internal oscillator can be modulated with a triangular carrier frequency of 23 kHz or 94 kHz, with a ±6 %

deviation range around the oscillator frequency. The spread spectrum feature and the carrier frequency can be

selected by SPI. The FSS_EN bit enables the spread spectrum feature and the FSS_FMOD bit selects high- or

low-frequency modulation. These two bits are in the M_SYS_CFG SPI register. By default, the spread spectrum

feature is disabled.

The main purpose of the spread spectrum feature is to improve EMC performance by spreading out the energy

of the internal oscillator and VPRE frequency. Because of this, NXP recommends enabling spread spectrum

and selecting the 23 kHz carrier frequency as the default for both VPRE switching frequencies.

TA = –40 °C to 125 °C, unless otherwise specified. VSUP_UVH < VSUP < 36 V, VPRE_PWM + VPRE_HDR < VSUP_PWR < 36 V, unless otherwise specified. All voltages

are referenced to ground.

Symbol

Description

Min

Typ

Max

Unit

Internal oscillator

High-frequency oscillator (OTP programmable)

FOSC_HIGH

CLK_FREQ_OTP[1:0] = 00

CLK_FREQ_OTP[1:0] = 01

CLK_FREQ_OTP[1:0] = 10

CLK_FREQ_OTP[1:0] = 11

—

MHz

FOSC_HIGH_ACC

High-frequency oscillator accuracy

-6

—

FOSC_LOW

Low-frequency oscillator

—

kHz

FOSC_LOW_ACC

Low-frequency oscillator accuracy

-5

—

Spread spectrum

Spread spectrum frequency modulation for 450 kHz

CLK_FREQ_OTP[1:0] = 00 (FSS_FMOD = 0, FSS_EN = 1)

CLK_FREQ_OTP[1:0] = 01 (FSS_FMOD = 0, FSS_EN = 1)

CLK_FREQ_OTP[1:0] = 10 (FSS_FMOD = 0, FSS_EN = 1)

CLK_FREQ_OTP[1:0] = 11 (FSS_FMOD = 0, FSS_EN = 1)

19.5

20.8

22.1

23.3

20.8

22.1

23.4

24.7

22.1

23.5

24.9

26.3

kHz

Spread spectrum frequency modulation for 2.25 MHz

FOSC_MOD

CLK_FREQ_OTP[1:0] = 00 (FSS_FMOD = 1, FSS_EN = 1)

CLK_FREQ_OTP[1:0] = 01 (FSS_FMOD = 1, FSS_EN = 1)

CLK_FREQ_OTP[1:0] = 10 (FSS_FMOD = 1, FSS_EN = 1)

CLK_FREQ_OTP[1:0] = 11 (FSS_FMOD = 1, FSS_EN = 1)

78.4

83.3

88.2

93.1

83.3

88.5

93.8

88.4

93.9

99.4

105

kHz

Table 113. Clock management electrical characteristics

FS26_SDS

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

Product short data sheet

Rev. 6.0 — 12 December 2025

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