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  • Power Management with System Basis Chip

  • Created: Aug 04, 2015

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This design is quite common to industrial application in which it helps to improve productivity of process control. It has fully protected embedded 5.0V regulator for the CAN driver and multiple undervoltage detections to address various MCU specifications and system operation modes. It is capable of multiple wake-up sources in LP modes such as CAN or LIN bus, I/O transition, automatic timer, SPI message, and VDD overcurrent detection. It is also ISO11898-5 high-speed CAN interface compatible for baud rates of 40kbps to 1Mbps.

The design circuit makes use of a MC34904C5EK system basis chip with CAN high speed interface. The supply can be VDC 5V or 3.3V regulated source. The V-AUX, V-BAUX, and V-CAUX, is used to provide auxiliary voltage output in which it uses an external PNP pass transistor at V-BAUX for flexibility and power dissipation constraints. The CAN interface is provided with termination as for ECU connection, and the configurations can be seen to several high level schematic of a CAN interface in which it has LS driver between CANL and GND, and a HS driver from CANH to 5V-CAN. The I/O pins are configurable in which in this case it is used to drive external transistors. The VSENSE incorporates a threshold detector to sense the battery voltage and provide a battery early warning and it includes a resistor divider to measure the VSENSE voltage via MUX-OUT pin. The VE and VB pin is used to allow usage of an external “P” type transistor, with the objective to share the power dissipation between the internal transistor of the VDD regulator and the external transistor. The SAFE pin is used to drive safe circuitry and set the ECU in a known state, independent of the MCU and SBC, once a failure has been detected. The serial ports including interrupts and reset are connected to the MCU for digital and/or analog control.

The design is applicable to industrial process control that uses MCU as the main controller while this system basis chip works as an advanced power management unit for that MCU. Aside of industrial applications, it is also applicable to robotics in which several MCUs are included.



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