AN4218 STMICROELECTRONICS | Alldatasheet
Document overview
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Technical content
Datasheet sections
- 1 System overview
- 1.1 Overview
- 1.2 Car-battery power supply (VBAT) transients
- 1.2.1 Example battery supply test pulses
- 1.2.2 Power-up-reset requirements of the SPC microcontrollers
- 2 Good practices of system power supply
- 2.1 Microcontroller power supply reactions on VBAT transients
- 2.1.1 L99PM62GXP block diagram
- 2.1.2 Measurement setup
- 2.1.3 Measurement results
- 3 Application circuits
- 3.1 Reference circuit
- 3.2 Implementation suggestions
- 3.2.1 Measurement of an permanently enabled power-supply (VMEASURE)
- 3.2.2 Bad practices
- 3.2.3 Physical layer
power supply and voltage measurement Introduction This document provides useful hints and suggestions about the implementation of the STMicroelectronics 32-bit microcontroller devices in an automotive system. The main focus has been set on the power supply concept and the connection to signals from different power domains. Due to the harsh conditions in the automotive environment several precautions have to be taken into account to ensure the robustness of the system. This is especially important when defining its power supply concept. This document shows test cases defined by car makers, which are intended to reproduce the system behavior in the real automotive environment, it also shows good practices to cope with them as well as bad practices and their influence on the system robustness.
1 System overview
1.1 Overview
layer transceiver and load drivers. voltage, either by a logic-level input/output or an analog-to-digital convertor (ADC). The inductances LS1 to LS4 are the parasitic wire inductances of the supply lines. voltage generated the by voltage controller inside the SBC. Protection resistors are added at the monitor inputs of the microcontroller. Figure 1. Microcontroller with power supply, drivers and physical layer
1.2 Car-battery power supply (V BAT) transients
the supply voltage for the microcontroller (VDD). Figure 2. Brown out Figure 3. Non strictly rising ramp Figure 4. Slow ramp Figure 5. Residual voltage
1.2.1 Example battery supply test pulses
car makers (see Appendix A: Reference documents). sharp voltage drop and ringing, which can be seen during the engine cranking. Figure 6. Test pulse E11 Table 1. Parameters sharp test pulse E11
As shown in Table 1 the ‘sharp’ pulse E11 on VBAT (UB) drops down to 3.2 V (UT). This tests the system behavior when the power supply is reversed.
1.2.2 Power-up-reset requirements of the SPC microcontrollers
supplying the microcontroller. Table 1. Parameters sharp test pulse E11 (continued)
Figure 7. VDD ramp-up/ ramp-down (SPC560Bxx, SPC560Cxx, – example only) Table 2. VDD ramp specification (SPC560P34x, SPC560P40x – example only)
Good practices of system power supply AN4218
2 Good practices of system power supply
2.1 Microcontroller power supply reactions on V BAT transients
This section shows the measurements done on a system-basis-chip L99PM62GXP, which provides the power supply (VDD) to the microcontroller. In addition to the microcontroller power supply this device provides also an NRESET output, which should be used to drive the microcontroller NRESET input for achieving maximum reliability of the microcontroller power-up state. The measurements have been taken from the STMicroelectronics In-Application-Validation- Report of the L99PM62GXP. This document is available on request.
2.1.1 L99PM62GXP block diagram
Figure 8 shows a typical ST system-basis chip, which contains voltage regulators to generate the supply for the microcontroller (output V1). Additionally it provides physical layer interfaces (LIN, CAN), a serial-parallel interface and various high-side and low-side drivers.
Figure 8. L99PM62GXP block diagram
2.1.2 Measurement setup
Figure 9. Measurement setup
2.1.3 Measurement results
output of the L99PM62GXP, if it is subject to the above defined test pulses. The parameter specification can be found in Table 1. Figure 10. Engine cranking pulse
high 2 ms after V1 has reached the NRESET high threshold. recovered ensures a correct power-up reset of the microcontroller. after V1 has reached the microcontrollers operating region. a defined state. This is additionally supported by the NRESET signal. Figure 13. VS voltage ramp up (0.5 V/min)
- Line 1 (RESET): NRESET output
NRESET threshold is reached NRESET goes to high. node and not on the battery voltage slope.
The NRESET goes high after V1 has reached the operating region of the microcontroller. state. This is additionally supported by the NRESET signal. Figure 14. VBAT voltage ramp down (0.5 V/min)
- Line 1 (RST): NRESET output
The NRESET goes low after V1 has left the operating region of the microcontroller. Therefore the microcontroller is always in a defined state.
3 Application circuits
3.1 Reference circuit
Figure 15. Reference circuit
3.2 Implementation suggestions
special care has to be taken on the following system parts.
3.2.1 Measurement of an permanently enabled power-supply (V MEASURE)
microcontroller is not influenced. damage the microcontroller. These ISO-transients are defined in ISO 7637-2:2011(E). the latest datasheet of the used device. DD, which supplies the ADC pin.
For further information please consult the actual datasheet of the used microcontroller. Figure 16. Voltage divider ESD-diodes if an ISO-transient occurs. These ISO-transients are defined in ISO 7637-2:2011(E). datasheet of the used device for the latest requirements.
Figure 17. ISO transients to clamp the positive pulse.
Figure 21. Backward current (0.7 Vtyp) higher than VDD-HV, thus violating the absolute maximum rating of 0.3 Vmax.
3.2.2 Bad practices
The circuit does not contain a protection resistor RPROT and no low-pass-filter.
Figure 22. Bad example circuit (see example above), the microcontroller might be damaged. improves this by adding a low resistive path to ground for high frequencies. microcontroller ESD protection diode is not actively sunk to ground. drivers etc.) they will get affected as well.
case only a very limited current is flowing through them. A continuous current may lead to a degrading effect on these diodes over time.
3.2.3 Physical layer
the bus this may lead to residual voltages while the microcontroller is not supplied. Figure 23. CAN-transceiver without reverse protection
Reference documents AN4218 Appendix A Reference documents 1. 32-bit Power Architecture ® based MCU for automotive powertrain applications (SPC560P34x, SPC560P40x — Doc ID 18078) 2. 32-bit MCU family built on the embedded Power Architecture ® (SPC564A74B4, SPC564A74L7, SPC564A80B4, SPC564A80L7 — Doc ID 15399) 3. 32-bit MCU family built on the Power Architecture ® for automotive body electronics applications (SPC560D30x, SPC560D40x — Doc ID 16315) 4. 32-bit MCU family built on the Power Architecture ® for automotive body electronics applications (SPC560B40x, SPC560B50x, SPC560C40x, SPC560C50x — Doc ID 14619) 5. 32-bit MCU family built on the Power Architecture ® for automotive body electronics applications (SPC560B54x, SPC560B60x, SPC560B64x — Doc ID 15131) 6. 32-bit MCU family built on the Power Architecture ® for automotive body electronics applications (SPC564Bxx, SPC56ECxx — Doc ID 17478) 7. 32-bit Power Architecture ® microcontroller for automotive SIL3/ASILD chassis and safety applications (SPC56EL60x, SPC56EL54x, SPC564L60x, SPC564L54x — Doc ID 15457) 8. 32-bit Power Architecture ® microcontroller for automotive SIL3/ASILD chassis and safety applications (SPC56EL70L3, SPC56EL70L5, SPC564L70L3, SPC564L70L5 — Doc ID 023953) 9. 32-bit Power Architecture ® based MCU with 320 KB Flash memory and 20 KB RAM for automotive chassis and safety applications (SPC560P34L1, SPC560P34L3, SPC560P40L1, SPC560P40L3 — Doc ID 16100) 10. 32-bit Power Architecture ® based MCU with 576 KB Flash memory and 40 KB SRAM for automotive chassis and safety applications(SPC560P44L3, SPC560P44L5, SPC560P50L3, SPC560P50L5 — Doc ID 14723) 11. 32-bit Power Architecture ® based MCU with 1088 KB Flash memory and 80 KB RAM for automotive chassis and safety applications (SPC56AP60x, SPC56AP54x, SPC560P60x, SPC560P54x — Doc ID 18340) 12. 32-bit Power Architecture ® based MCU for automotive powertrain applications (SPC563M64L5, SPC563M64L7 — Doc ID 14642) 13. Power management IC with LIN and high speed CAN (L99PM62GXP , Doc ID 15136) 14. ISO 7637-2:2011(E) 15. ISO16750-2:2006 16. BMW GS95024-2-1 17. Renault 36-00-808 / 2010 18. VW 80000: 2009-10
Revision history
Table 3. Document revision history 04-Mar-2013 1 Initial release. 17-Sep-2013 2 Updated Disclaimer.