Part # Application Note General Purpose Products M40SZ100W M40SZ100Y M40Z111 M40Z111W M40Z300AV M40Z300W STM817LM STM818LM STM819LM datasheet

Part Manufacturer: ST Microelectronics

ST Microelectronics

Part Description: ZEROPOWER and TIMEKEEPER supervisor surface-mount solution


Part Details:

AN1957 APPLICATION NOTE Microprocessor Supervisor Functions Designers of microprocessor systems have to achieve high reliability, in the face of a large number ofthreats to stability or even correct functioning (such as, voltage drops, glitches, long ramp-up times, pro-grams stuck in endless loops, etc.). Supervisor circuits, from STMicroelectronics, provide highly effective solutions for minimizing the risks ofsystem failure, and for ensuring the safe running of the system, at a low cost. The members of the STSupervisor family offer various combinations of functions. This Application Note describes the main Supervisor functions and features, to help the user to under-stand their principles and the advantages of using them, through the description of waveforms, recom-mended values, and hardware hookup diagrams. Overview of ST Supervisors ­ Microprocessor SupervisorsSTM705, STM706, STM706T/S/R, STM707, STM708, STM708T/S/R, STM813L, STM706P, STM6321L/M, STM6321T/S/R, STM6821L/M, STM6821T/S/R, STM6823L/M, STM6823T/S/R, STM6824L/M, STM6824T/S/R, STM6825L/M, STM6825T/S/R ­ Microprocessor Supervisors with SwitchoverM40SZ100W, M40Z111, M40Z300W, STM690A, STM692A, STM690T/S/R, STM802L/M, STM802T/S/R, STM703, STM704, STM704T/S/R, STM806T/S/R, STM805L, STM805T/S/R, STM804T/S/R, STM817L/M, STM818L/M, STM819L/M, STM795T/S/R ­ TIMEKEEPERTM SupervisorsM41ST95W, M41ST87W, M41ST87Y, M41ST85W, M41ST85Y, M41T315V, M48T201V, M48T201Y, M48T212V This Application Note is dedicated to the Microprocessor Supervisor and Microprocessor Supervisor withSwitchover families. March 2005 1/22 AN1957 - APPLICATION NOTE TABLE OF CONTENTS Overview of ST Supervisors . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1Table 1. Supervisor Options . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4 POWER-ON RESET AND LOW VOLTAGE DETECT . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5 Block Diagram Showing the Supervisor Reset Feature . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5Figure 1. Supervisor Reset Features . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5Reset Waveforms for the Microprocessor Supervisor Devices . . . . . . . . . . . . . . . . . . . . . . . . . 6Figure 2. Power-On Reset and Low Voltage Detect Waveforms . . . . . . . . . . . . . . . . . . . . . . . . . . . 6Table 2. Reset Timings for the STM703/704 Supervisor. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6Table 3. Reset Thresholds (VRST) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6Hardware Hookup for the STM703/704 Supervisor . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7Figure 3. Hardware Hookup for the STM703/704 Supervisor. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7 POWER-FAIL COMPARATOR . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8 Block Diagram of a Power-Fail Comparator . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8Figure 4. Block Diagram of a Power-Fail Comparator . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8Hardware Hookup for the STM692A Supervisor. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8Example calculation. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8Table 4. Recommended Resistances for some VTRIP Voltages . . . . . . . . . . . . . . . . . . . . . . . . . . . 9Figure 5. Hardware Hookup for the STM692A Supervisor . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9Example of Power-Fail Waveforms . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10Figure 6. Voltage Drop . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10Table 5. Power-Fail Values for all Microprocessor Supervisors (except for the devices mentioned in Table 6.). . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10 Table 6. Power-Fail Values for 3V Microprocessor Supervisors with Battery Switchover (STM690/704/802/804/805/806) . . . . . . . . . . . . . . . . . . . . . . . . 10 WATCHDOG TIMER . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 11 Figure 7. Logic Diagram of a Watchdog Timer . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 11Figure 8. Watchdog Timer Input and Output Waveforms . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 11Table 7. Watchdog Timer Time-out Value for the STM705 Supervisor . . . . . . . . . . . . . . . . . . . . . 11Hardware Hookup for the STM705 Supervisor . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 12Figure 9. Hardware Hookup for the STM705 Supervisor . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 12 BATTERY SWITCHOVER. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 13 Figure 10.Block Diagram of a Battery switchover Device . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 13Switchover Waveforms for the STM806R Supervisor . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 14Figure 11.Battery Switchover Waveforms for the STM806R Supervisor. . . . . . . . . . . . . . . . . . . . . 14Figure 12.Switchover Waveforms with Hysteresis Details . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 15Table 8. Switchover Values for the STM806R Supervisor. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 15Hardware Hookup for the STM806R Supervisor. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 16Figure 13.Hardware Hookup for the STM806R Supervisor . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 16Hardware Hookup for the STM795 Supervisor . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 16Figure 14.Hardware Hookup for the STM795 Supervisor . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 16 2/22 AN1957 - APPLICATION NOTE CHIP ENABLE GATING . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 17 Figure 15.Chip Enable Gating Block Diagram . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 17Typical Waveforms for the STM818 Supervisor . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 18Figure 16.Typical Waveforms for the STM818 Supervisor . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 18Table 9. Typical values for the STM818 Supervisor . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 18Hardware Hookup for the STM818 Supervisor . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 19Figure 17.Hardware Hookup for the STM818 Supervisor . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 19 BATTERY FRESHNESS SEAL . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 20 Figure 18.Typical Waveforms for the STM817/818/819 Supervisors . . . . . . . . . . . . . . . . . . . . . . . 20 CONCLUSION . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 20 REFERENCES . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 21 REVISION HISTORY . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 21 Table 10. Document Revision History . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 21 3/22 Document Outline Overview of ST Supervisors Table 1. Supervisor Options POWER-ON RESET AND LOW VOLTAGE DETECT Block Diagram Showing the Supervisor Reset Feature Figure 1. Supervisor Reset Features Reset Waveforms for the Microprocessor Supervisor Devices Figure 2. Power-On Reset and Low Voltage Detect Waveforms Table 2. Reset Timings for the STM703/704 Supervisor Table 3. Reset Thresholds (VRST) Hardware Hookup for the STM703/704 Supervisor


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Application Note General Purpose Products M40SZ100W M40SZ100Y M40Z111 M40Z111W M40Z300AV M40Z300W STM817LM STM818LM STM819LM.pdf Datasheet