NXP FS27_PB: Safety System Basis Chip with Low Power for ASIL D/ASIL B

General Description

The FS27 family comprises several pin-to-pin and software-compatible versions, catering to a wide range of applications with ASIL B or D safety integrity levels. These versions offer choices in output rails, voltage settings, operating frequencies, power-up sequencing, and integrated system-level features. The chip incorporates multiple switch-mode regulators and low-dropout (LDO) voltage regulators to supply the microcontroller, sensors, peripheral ICs, and communication interfaces. It provides a high-precision reference voltage supply and two independent tracking regulators. Additionally, the FS27 includes functionalities for system control and diagnostics, such as an analog multiplexer, general-purpose input/outputs (GPIOs), and selectable wake-up events via I/O, timers, SPI, or I²C communications. Developed in compliance with the ISO 26262 standard, the FS27 features enhanced safety with multiple fail-safe outputs and on-demand latent fault monitoring, supporting safety-oriented system partitioning for both ASIL B and ASIL D levels.

Features and Benefits

Operating Range

• 70 V DC maximum input voltage
• Supports operating voltage down to 3.2 V with VBST in front-end
• Supports operating voltage down to 3.2 V without VBST in front-end
• Low Power LPOFF mode with 30 µA quiescent current
• Low Power standby mode with 32 µA quiescent current with VPRE active (LDO1 or LDO2 activation selectable via OTP, GPIO1/GPIO2 activation via SPI/I²C)
• Low Power Run mode (LPRUN) with selectable power rails configurable by software

Power Supplies

• VPRE: Synchronous buck converter with integrated FETs, configurable output voltage and switching frequency, up to 1.5 A or 2.5 A DC current, PFM mode for Low Power standby.
• VCORE: Synchronous buck converter with integrated FETs, dedicated for microcontroller core supply, up to 2.5 A or 3.5 A DC current, output voltage range from 0.8 V to 5 V.
• VBST: Asynchronous low-side controller with external low-side switch, diode, and current sense resistor. Configurable as front-end supply for low-voltage cranking profiles, or back-end supply with configurable output voltage and scalable DC current capability. Supports SEPIC controller for 24 V applications and flyback controller for 48 V applications.
• LDO1: LDO regulator for microcontroller I/O support, selectable output voltage from 1.0 V to 5.0 V, up to 400 mA current capability.
• LDO2: LDO regulator for system peripheral support, selectable output voltage from 1.0 V to 5.0 V, up to 400 mA current capability.
• VREF: High-precision reference voltage with 0.75% accuracy for External ADC and internal tracking reference.
• TRK1 and TRK2: Voltage tracking regulators with selectable output voltage (VREF, LDO2, or Internal LDO reference). Support high-voltage protection for ECU off-board operation up to 40 V. Current capability up to 150 mA each.

System Support

• Two wake-up inputs with high-voltage support for system robustness
• Two programmable GPIO with wake-up capability or LS driver for GPIO1 and HS/LS driver for GPIO2
• Programmable long duration timer (LDT) for system shutdown and wake-up control
• System voltage monitoring (including battery voltage) via analog multiplexer
• Selectable wake-up sources: WAKE/GPIO pins, LDT, or SPI/I²C activity
• Device control via 32-bit SPI or 40-bit I²C interface with cyclic redundancy checks (CRC)
• Multi PMIC power-up/down synchronization
• DCLINK capacitor discharge command with NXP GD3163

Compliance

• Electromagnetic compatibility (EMC) optimization for switching regulators (spread spectrum, slew rate control, manual frequency tuning).
• Electromagnetic interference (EMI) robustness supporting automotive EMI test standards.

Functional Safety

• Scalable portfolio from ASIL B to ASIL D
• Independent monitoring circuitry, dedicated interface for microcontroller monitoring, simple or challenger watchdog function
• Analog built-in self-test (ABIST1) and logical built-in self-test (LBIST) at start-up
• Analog built-in self-test (ABIST2) on demand
• Safety outputs with latent fault detection mechanism (RSTB, FS0B/LIMP, FS1B)

Configuration and Enablement

• LQFP48 package with exposed pad for optimized thermal management
• Permanent device customization via one-time programmable (OTP) fuse memory
• OTP emulation mode for hardware development and evaluation
• Debug mode for software development, MCU programming, and debugging

Simplified Application Diagram

The document includes several figures illustrating simplified application diagrams for the FS27. These diagrams show the integration of the FS27 with a microcontroller (MCU) and other system components, demonstrating different configurations such as:

• Figure 2: Example of application diagram with VBST as a front-end regulator, supporting battery cold-crank events.
• Figure 3: Example of application diagram with VBST as a back-end regulator, generating a voltage above the high-voltage buck output voltage.
• Figure 4: Example of application diagram with a low-side controller as SEPIC, supporting 24 V and 48 V battery applications.
• Figure 5: Example of application diagram with a low-side controller as Flyback, supporting 48 V battery applications.

These diagrams highlight the connectivity of various FS27 internal blocks (VPRE, VCORE, LDO1, LDO2, VREF, TRK1, TRK2, VBST, WAKE, Analog and digital monitoring, Fail-safe state machine) to the MCU and external components like sensors and actuators.

Ordering Information

The FS27_PB product brief details part numbers available for purchase and explains how the part number reference is constructed. Table 1 provides a non-exhaustive list of part number examples, segmenting devices based on their low-side controller type (Boost, SEPIC, Flyback), VPRE and VCORE current capabilities, watchdog type, LBIST, safe state pin, FS1B, DCLINK discharge, and FCCU monitoring features.

Table 2 lists orderable part numbers, such as PFS2700BMDA0AD (Blank B0 superset FS0B prototype version) and PFS2702BMDA0AD (Blank B0 superset LIMP prototype version), both in LQFP48 package.

Applications

The FS27 is suitable for a wide range of automotive applications, including:

xEV and Powertrain Market

• Inverter
• Onboard charger (OBC), DCDC
• Battery management system (BMS)
• Belt starter generator (BSG)

Body Market

• Gateway
• Zonal control
• Body controller
• Smart junction box

Safety and Chassis

• Suspension
• Power steering

MCU Attach

The FS27 is compatible with various high-end MCUs, including:

• S32K3xx family
• Infineon Aurix family (TC4x)
• Renesas RH850 family
• ST SR6 family

Power Management

Table 3 summarizes the voltage regulator specifications for the FS27:

Package Information

Package dimensions are detailed in package drawings. For the most current package outline drawing, visit www.nxp.com and search for the drawing's document number. Table 4 specifies the mechanical dimensions for the 7.0 mm × 7.0 mm, 48-pin LQFP exposed pad package (Suffix AE, Drawing number 98ASA00945D).

Revision History

Table 5 indicates that the document FS27_PB v.1.0 was released on 19 June 2025 as the initial version.

Legal Information

This section provides important notices regarding the document and products described. It covers definitions, disclaimers on warranty and liability, the right to make changes, application suitability, terms and conditions of commercial sale, and intellectual property rights. NXP Semiconductors reserves the right to make changes to specifications and product descriptions without notice. Customers are responsible for the design and operation of their applications using NXP products and must ensure suitability and compliance with all legal, regulatory, safety, and security requirements. NXP B.V. is not an operating company and does not distribute or sell products.

Trademarks

NXP wordmark and logo are trademarks of NXP B.V. SafeAssure is a trademark of NXP B.V.