Infineon TLF35584: ASIL-D Safety PMIC for Automotive
Overview
The TLF35584 from Infineon is a multi-voltage safety power management IC designed to supply and monitor automotive microcontrollers in safety-relevant electronic control units (ECUs). It integrates a pre-regulator buck stage, several post-LDOs, a voltage reference, tracking regulators, and a supervised watchdog into one device, and it is qualified to support ISO 26262 ASIL-D systems. This article covers the device architecture, key specifications, typical ECU applications, and design considerations for engineers evaluating it for automotive platforms.
Part Overview
The TLF35584 belongs to Infineon's OPTIREG family of automotive PMICs. Its primary role is to take the raw vehicle battery voltage (through a pre-regulator stage) and generate the clean, monitored rails required by a safety MCU such as Infineon AURIX TC2x or TC3x, or Renesas TRAVEO T1G devices. The device is supplied in two main variants: TLF35584xxVS1 provides a 5.0 V microcontroller supply rail, while TLF35584xxVS2 provides a 3.3 V microcontroller supply rail. Both variants include a low-dropout communication LDO, a precision reference LDO, two tracking LDOs for external sensors, and a standby LDO for always-on circuits. Integrated safety features include a watchdog with error signaling, reset generation, voltage monitoring, and a clock evaluation capability. The device also provides enable and sync signals to control an optional external post-regulator for the MCU core supply, which allows the core rail to be generated externally while the TLF35584 supervises it.Key Features
Wide-input pre-regulator buck stage operating from 6.0 V to 40 V vehicle supply, supporting cold-crank and load-dump conditions.
Microcontroller supply LDO at 5.0 V or 3.3 V, rated at 600 mA, depending on variant.
Precision voltage reference LDO at 5.0 V with 150 mA output and approximately 1% accuracy, intended for the MCU ADC reference.
Two tracking LDO outputs at 5.0 V, 150 mA each, that follow the MCU supply for external sensor bridges.
Communication LDO at 5.0 V, 200 mA, for CAN or transceiver supplies.
Standby LDO at 3.3 V or 5.0 V, 10 mA, for always-on logic.
Safety watchdog with question/answer mode and reset output.
Voltage monitoring and power-good supervision across all rails.
AEC-Q100 qualified and developed according to ISO 26262, with a safety manual available to system integrators.
Key Specifications
Input voltage range: 6.0 V to 40 V (per datasheet)
Pre-regulator buck output current: up to 1.3 A (per vendor product page)
Pre-regulator switching frequency: 300 kHz to 2.5 MHz (per vendor documentation)
MCU supply LDO: 5.0 V/600 mA (VS1) or 3.3 V/600 mA (VS2)
Reference LDO: 5.0 V/150 mA, 1% accuracy
Tracking LDOs: 2 x 5.0 V/150 mA
Communication LDO: 5.0 V/200 mA
Standby LDO: 3.3 V or 5.0 V/10 mA
Quiescent current: approximately 70 uA (typical, per vendor)
Functional safety rating: ISO 26262 ASIL-D capable
Package: PG-TSDSO-14 (per vendor)
Operating temperature: -40 C to +150 C junction (per datasheet)
Applications and Design Notes
The TLF35584 is intended for safety-critical automotive ECUs such as electric power steering, brake systems, airbag control, battery management, and transmission control units. In a typical AURIX-based design, the pre-regulator buck output feeds the post-LDOs, which in turn power the MCU I/O, core supply (through an external regulator), ADC reference, and external sensor circuitry. The communication LDO powers the CAN/LIN transceiver, and the standby LDO maintains the always-backup domain during sleep modes. Design notes:The pre-regulator inductor and input/output capacitors must be rated for automotive transient and ripple conditions; follow the datasheet application table for component selection.
The tracking LDOs are designed to track the MCU supply within a small offset; load the external sensor bridges symmetrically to keep tracking accuracy within spec.
Route the watchdog and reset lines with dedicated traces; do not share them with noise-sensitive analog lines.
The safety manual defines which pins must be connected and which monitoring paths are required to claim ASIL-D compliance at the system level.
Design Considerations and Common Mistakes
Do not treat the TLF35584 as a general-purpose PMIC: its safety documentation and watchdog behavior are designed for certified systems, and bypassing monitoring features will invalidate the ASIL-D claim.
The 40 V input rating must account for load-dump pulses; if the ECU is directly battery-connected without external clamping, confirm the surge protection strategy against the OEM's test specification.
Undersizing the pre-regulator inductor is a common error: saturation current must cover peak switch current plus margin over the full voltage and temperature range.
The standby LDO quiescent budget matters in automotive sleep modes; calculate total sleep current including the MCU, transceiver, and TLF35584 itself to meet the ECU's current-drain specification.
Because the device supervises an external core regulator, the enable and feedback paths must be laid out with proper impedance and filtering; a noisy core-supply feedback can trigger false reset events.
Conclusion
The TLF35584 is a purpose-built automotive safety PMIC that combines multiple regulated rails with integrated supervision in a single package. Its ASIL-D capability, wide input range, and direct support for AURIX and TRAVEO microcontrollers make it a common choice in safety-relevant ECU designs where external supervision circuits would otherwise add board area and qualification burden.
FAQ
Q: What is the difference between the VS1 and VS2 variants?
A: VS1 provides a 5.0 V microcontroller supply LDO, while VS2 provides a 3.3 V microcontroller supply LDO. All other rails and safety functions are the same between the two variants.
Q: Can the TLF35584 power the MCU core directly?
A: No. The device supervises and enables an external post-regulator for the MCU core supply. The TLF35584 itself provides the I/O, reference, sensor, communication, and standby rails.
Q: Does the TLF35584 require an external microcontroller to handle the watchdog?
A: The watchdog is integrated in the PMIC and communicates with the MCU through a dedicated watchdog pin. The MCU must respond correctly to watchdog triggers; the PMIC generates a reset or error signal if it does not.
Q: What vehicle voltage range does the device support?
A: The pre-regulator operates from 6.0 V to 40 V, covering nominal 12 V battery systems including cold-crank dips and load-dump transients within the device's ratings.
For exact specifications and design guidance, refer to the official Infineon datasheet for TLF35584.
Top comments (0)