ASIL-D Multi-Rail Power Supplies for MCUs with Rotation CounterApril 10, 2020 by Paul Shepard
The TPS653853A-Q1 and TPS653854A-Q1 devices from Texas Instruments are multi-rail power supplies designed to supply microcontrollers in safety relevant applications, such as those found in the automotive industry. The devices support functional safety microcontrollers with dual-core lockstep (LS) and other multi-core architectures.
The TPS653853A-Q1 and TPS653854A-Q1 integrate multiple supply rails to power the MCU, CAN or FlexRay, and external sensors. A buck-boost converter with internal FETs converts the input battery voltage between 2.V and 36 V to a 6-V preregulator output that supplies the other regulators. An integrated charge pump provides an overdrive voltage for the internal regulators, and can also be used to drive an external NMOS FET as reverse battery protection. The device supports wake-up from an ignition signal (IGN pin) or wake-up from a CAN transceiver or other signal (CAN_WU pin).
The devices have a steering-angle monitoring (SAM) unit that allows the ECU to indirectly capture the position of the steering wheel through the motor-position sensors. A dedicated low-power mode allows this SAM unit to operate even when the ECU is in sleep mode. Integrated SAM-switches allow passing-through of the Motor-Position Sensor signals to the MCU during normal operation, or decoupling the MCU ADC inputs from the motor-position sensor signals when the ECU is in sleep mode.
An independent voltage monitoring unit inside the device monitors undervoltage and overvoltage on all internal supply rails and regulator outputs of the battery supply. Regulator current limits and temperature protections are also implemented.
The TPS653853A-Q1 and TPS653854A-Q1 feature a question-answer watchdog, MCU error-signal monitor, clock monitoring on internal oscillator, self-check on clock monitor, cyclic redundancy check (CRC) on non-volatile memory and SPI communication, a diagnostic output pin allowing MCU to observe device internal analog and digital signals, a reset circuit for the MCU (NRES pin) and a safing output (ENDRV pin) to disable external power-stages on any detected system-failure.
The devices automatically run a built-in self-test (BIST) at start up and the MCU may re-run the BIST during system run time through software control if needed. A dedicated DIAGNOSTIC state allows the MCU to check TPS653853A-Q1 and TPS653854A-Q1 functionality.
The TPS653853A-Q1 and TPS653854A-Q1 also have an error reporting capability through the SPI register. The devices have separate status bits in the SPI register for each specific error on the system level or device level. When the device detects a particular error condition, it sets the appropriate status bit and keeps this status bit set until the MCU reads-out the SPI register in which this status bit was set. Based on which status bit was set, the MCU can decide whether it must keep the system in a safe state or whether it can resume with the operation of the system.
The TPS653853A-Q1 and TPS653854A-Q1 are available in a 48-pin HTSSOP PowerPAD™ IC package.