Serial real-time clock (RTC) ICs

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1 Serial real-time clock (RTC) ICs

2 Content Real-time clock (RTC) ICs spectrum... 3 Low-power real-time clocks for portable devices... 4 World s smallest RTC with embedded crystal... 5 Enhanced industry-standard real-time clocks... 6 Highly accurate, automatic temperature-compensated real-time clock solution with embedded crystal... 6 Real-time clocks with analog calibration... 8 Highly-integrated real-time clocks Combined RTC and microprocessor supervisor Securitizor Design support... 16

3 RTC ICs spectrum Widest portfolio of real-time clocks offers unlimited designs solutions An extended variety of products with the newest technology innovations are available including ultralow-power devices, the world s smallest package with embedded crystal, ST s SNAPHAT with battery and crystal integrated. RTC functions include alarm, battery switchover, reset, and special features with time stamp, anti-tamper for secure applications, audio, and trickle charge, and an highly-accurate temperature-compensated RTC with embedded crystal. Low-power for portable devices Enhanced industry-standard Highly-integrated Securitizor Low standby current World s smallest RTC with crystal Small packages Automatic battery switchover Analog calibration Embedded crystal Temperature-compensated RTC RTC with NVRAM and microprocessor supervisor functions monitor Power-on reset/low-voltage detect Physical tamper detect Internal and external RAM clear Tamper event timestamp M41T6x series M41T81S, M41T00S, M41T82/83/93, M41T00CAP, M41TC8025 M41ST85W, M41T94, M41T00AUD M41ST87W 3 Integration

4 Low-power RTC ICs Very low standby current extends battery backup life Special low-power RTC series available in small packages, from 350 na, with battery switchover, and with or without an embedded crystal to best fit battery-operated device constraints. M41T6x 10ths and 100ths of seconds 350 na standby (typ) at 3.0 V 1.3 to 4.4 V operation 4.4 V max suitable for lithium-ion battery operation Timekeeping down to 1.0 V 400 khz I 2 C Interface Programmable watchdog output 62.5 ms to 31 min Dedicated output BCD registers for year, month, day, date, hours, minutes and seconds 2 century bits (Y2.1 K compliant) Automatic leap year adjustment Calibration register Oscillator fail detect 0.90 mm M41T6x 3 mm 3 mm QFN16 Application examples Digital cameras Portable media players Medical instruments Point-of-sale terminals Test equipment Portable navigation 4 Low-power RTCs for portable devices portfolio Part number Package supply current (Ibat) typ (na) Data bus type 400 khz Supply voltage min - max (V) Timekeeping min (V) Oscillator fail detect Programmable alarms timer Square wave dedicated ouput Power-up output frequency (khz) Embedded crystal M41T60 QFN I 2 C M41T62 QFN I 2 C LCC8 350 I 2 C M41T63 QFN I 2 C M41T64 QFN I 2 C M41T65 QFN I 2 C M41T66 QFN I 2 C Note: 1: With IRQ output

5 World s smallest RTC with embedded crystal M41T62LC6F RTC in LCC8 package with embedded crystal 10ths and 100ths of seconds Programmable alarm with repeat modes and interrupt function Programmable watchdog timer 62.5 ms to 31 min Programmable square-wave output 1 Hz to and on at power-up (can be disabled) 1.5 mm LCC8 3.2 mm XI XO Microcontroller 2 oscillator 400 khz interface M41T62 Day Century bits Alarm Out Oscillator fail detect Square wave Calibration OFIE IRQ/OUT (Open drain) SQW 5

6 Enhanced industry-standard Class-leading RTCs for smart utility meters and precision applications Enhanced industry-standard RTC with fixed reference added for highly-reliable battery switchover threshold, plus analog calibration, embedded crystal and oscillator fail detect. Highly accurate, automatic temperature-compensated real-time clock solution with embedded crystal More applications now require very accurate timekeeping across a wide range of temperature. Multi-rate smart power metering is a typical example,since power companies need to log multi-rate electricity usage for accurate billing. Applications: Smart metering and industrial. M41TC8025 Embedded high-stability DTCXO M41TC8025 Temperature-compensated serial real-time clock ±5.0 ppm max from -40 to 85 C ±3.8 ppm max from 0 to 50 C Temp sensor Compensation control temp-compensated OSC & capacitor array Interrupt control 6 Supply voltage Clock operating & timekeeping: 1.6 to 5.5 V I 2 C interface operating: 1.8 to 5.5 V Temperature compensation: 2.2 to 5.5 V 0.8 μa typical current at 3.0 V supply voltage 400 khz I 2 C interface Time-of-day alarm (with interrupt) Fixed-cycle timer interrupt function Time update interrupt function SDA SCL interface Time update Fixed-cycle timer Alarm compare Clock registers Day-of-week 1 Hz Divide by Hz Counter 0-59 Counter 0-59 UIE TIE AIE 1 KHz IRQ FOUT SQW FOE Programmable frequency output F OUT = 1 Hz, 1 KHz and Registers for seconds, minutes, hours, day-of week, date (day of month), month and year with automatic leap year compensation Programmable temperature compensation intervals (0.5 s, 2 s default, 10 s, 30 s) VSS Alarm registers Min alarm Hour alarm Day/week alarm alarm Non-clock registers Time counter 0 Time counter 1 Extension reg Flag register Control reg Counter 0-23 Counter 1-7 Counter 1-31 Counter 1-12 Counter 0-99 SO14

7 M41T00S Precision reference for battery switchover threshold Oscillator fail detect circuit 400 khz I 2 C interface Automatic battery switchover and write-protect Calibration register - accuracy to 5 seconds per month BCD registers: century, year, month, day, date, hours, minutes, seconds 2.7 to 5.5 V operation Automatic leap year adjustment SO8 package Microcontroller 2 XI XO Automatic battery switchover and write protect Reference VPFD = 2.6 V 400 KHz interface oscillator M41T00S Day Century bits Calibration Out Oscillator fail detect FT/OUT/ OSC-FAIL-IRQ M41T00CAP Integrated backup battery and embedded crystal Based on M41T00S RTC CAPHAT PCDIP24 package 0 to 70 C operation Up to 10 years of timekeeping without system power M41T00AUD RTC with integrated audio amplifier 400 khz I 2 C interface DFN16 (5 x 4 mm) package 0 to 70 C operation 400 na backup current 3.0 to 3.6 V operation Automatic battery switchover Audio features 300 mw differential audio amplifier 256 and 512 Hz tone generation Gain adjustment from - 33 to +12 db in 3 db steps Automatic shut off in backup mode 7 Oscillator fail detect PCDIP24 CAPHAT Embedded crystal + battery (internal view) Trickle charge circuit for backup capacitor Timekeeping down to 1.7 V M41T81S Precision reference for battery switchover threshold Programmable alarm with repeat modes Oscillator fail detect circuit monitor Automatic battery switchover and write-protect Calibration register - accuracy to 5 seconds per month BCD registers: century, year, month, day, date, hours, minutes, seconds 400 khz I 2 C interface Programmable watchdog 62.5 ms to 128 s time-out Programmable square-wave 1 Hz to Automatic leap year adjustment Microcontroller XI XO 2 Automatic battery switchover and write protect Reference VPFD = 2.6 V monitor 400 KHz interface oscillator M41T81S Day Century bits Calibration Alarm Square wave Oscillator fail detect Out SOX18 Embedded crystal (Internal view) SO8 FREQ-TEST/ ALARM/ W-DOG/ SQ-WAVE/ OSC-FAIL-IRQ/ OUT

8 Real-time clocks with analog calibration M41T83, M41T93 Dual calibration features Analog calibration 5 ppm typical at 25 C after two reflows Real-time feedback Pre-programmed in OTP byte (only in

0 V Microcontroller Automatic battery switchover and write-protect Precision reference 400 khz I 2 C, 10 MHz SPI 12 bytes of NVRAM 5 bytes shared with 2 alarm registers 2 programmable alarms with

8 8 Real-time clocks with analog calibration M41T83, M41T93 Dual calibration features Analog calibration 5 ppm typical at 25 C after two reflows Real-time feedback Pre-programmed in OTP byte (only in SOX18) Digital calibration 365 na standby (typ) at 3.0 V Microcontroller Automatic battery switchover and write-protect Precision reference 400 khz I 2 C, 10 MHz SPI 12 bytes of NVRAM 5 bytes shared with 2 alarm registers 2 programmable alarms with repeat modes Memory-mapped BCD year, month, day, date, hours, minutes, seconds, 10ths, 100ths of seconds 2.38 to 5.5 V operation Timekeeping down to 1.8 V Three V PFD (V RST ) options: 2.93 V 3.0 to 5.5 V CC 2.63 V 2.7 to 5.5 V CC 2.32 V 2.38 to 5.5 V CC Programmable watchdog (62.5 ms to 128 s) Programmable squarewave output 1 Hz to on at power-up (can be disabled) 0.90 mm /SPI M41T83 4 mm VBAT VPP (SOX18 only) 2/4 / SPI 4 mm QFN16 Automatic battery switchover and write protect Reference V PFD (VRST) = 2.6 V monitor 400 KHz T83 SPI: T93 oscillator M41T83, M41T93 Day 2 Century bits A. cal (REG) A. cal (OTP) D. cal Alarm1 Alarm2 Oscillator fail detect Out Auto-reload 8-bit tmr/cntr Square ware NVRAM 12 bytes SOX18 Embedded crystal (internal view) POR/LVD OTP only on SOX18 package IRQ2 IRQ/FT/OUT (W-DOG/ ALARM-IRQ/ FT/OUT/ OSC-FAIL-IRQ/ TIMER-IRQ) SQW (Defaults to and on; can be disabled) M41T82 Light version of M41T83, pin-to-pin compatible with earlier RTCs in SO8 packages Dual calibration features Analog calibration - real-time feedback Digital calibration Automatic battery switchover and writeprotect Precision reference 400 khz I2C 365 na standby (typ) at 3.0 V 12 bytes of NVRAM 2.38 to 5.5 V operation SO8 Timekeeping down to 1.8 V Three VPFD (VRST) options: 2.93 V 3.0 to 5.5 V CC 2.63 V 2.7 to 5.5 V CC 2.32 V 2.38 to 5.5 V CC Memory-mapped BCD year, month, day, date, hours, minutes, seconds 10ths, 100ths of seconds Microcontroller VBAT 2 XI XO Automatic battery switchover and write protect Reference V PFD (VRST) = 2.6 V monitor 400 KHz oscillator M41T82 Day 2 Century bits Analog cal Digital cal Oscillator fail detect Auto-reload 8-bit tmr/cntr NVRAM 12 bytes POR/LVD

9 Long-life battery backup 48 mah battery 12 years backup life M41T56 battery backup Backup life t = battery capacity / battery current BR1225 capacity = 48 mah M41T56 backup current IBAT = 450 na (typical) Backup life t = BR1225 capacity / I BAT t = 48 mah / 450 na = 106,666.7 hours = days Backup life t = 12.2 years VBAT BR1225 Li coin cell = 5 V M41T56 VBAT VSS Application examples Home multimedia Metering (gas, electricity, water) Multi-function printers Vehicle tracking systems Enhanced industry-standard RTCs portfolio Part number Package supply current (Ibat) typ (na) NVRAM size (bytes) Data bus type V CC min - max (V) Timekeeping min (V) switchover Oscillator fail detect Programmable alarms Square wave output Power-up output frequency (khz) timer low detect Power on Reset/low voltage detector output Embedded crystal Temperature compensated M41T0 SO M41T00S SO M41T00AUD DFN M41T00CAP PCDIP M41T11 SO SOH M41T56 SO M41T80 SO M41T81S SO SOX M41T82 SO M41T83 M41T93 QFN SOX QFN SPI SOX SPI M41TC8025 S Note: 1: Integrated battery and embedded crystal 2: 400 khz 3: With IRQ output 4: Dedicated output 5: Fixed switchover reference 6: 10 MHz

10 Highly-integrated RTC Combined RTC and Microprocessor supervisor Highly-integrated RTCs with NVRAM and a large set of microprocessor supervisory functions, including battery monitor, power-on reset and low-voltage detect. 10 M41T94 Automatic battery switchover Power-fail detect and write-protect 2 MHz SPI bus THS pin selects 5 or 3/3.3 V operation 400 na standby (typ) at 3.0 V 44 bytes of NVRAM Programmable alarm with repeat mode Programmable square-wave output 1 Hz to 10ths and 100ths of seconds Microprocessor supervisor functions Power-on reset/low-voltage detect Programmable watchdog 62.5 ms to 128 s Microprocessor THS I/O XTAL 4 SPI Automatic battery switchover VBAT monitor VSS Power-fail detect and Power-fail write Threshold protect 1: VPFD = 4.40 V 0: VPFD = 2.65 V WDI oscillator SPI M41T94 Day Century bits Calibration Alarm Square wave 44 Bytes NVRAM WDF AF IRQ/FT/OUT SQW Two reset inputs Application examples Servers RESET RST Power-on reset/low-voltage detect Push-button reset reset RSTIN1 RSTIN2 Medical equipment Point of sales IRQ Vending machines Gaming SO16 SNAPHAT battery top SOH28

11 M41ST85W 400 khz I 2 C 400 na standby (typ) at 3.0 V 2.7 to 3.6 V 28-lead SNAPHAT IC (SOH28) 28-lead embedded crystal SOIC (SOX28) Operating temperature: -40 to +85 C 44 bytes of NVRAM Programmable alarm with repeat mode Programmable square-wave output 1 Hz to 10ths and 100ths of seconds Microprocessor supervisor functions Early power-fail warning (PFI/PFO) with 1.25 V reference Power-on reset/low-voltage detect Programmable watchdog 62.5 ms to 128 s Two reset inputs SOH28 SNAPHAT IC NVRAM supervisor features Automatic battery switchover and write-protect Non-volatile external LPSRAM monitor SNAPHAT battery top SOX28 Embedded crystal (internal view) VUNREG Regulator CE VBAT VSS EX M41ST85W backup switchover monitor Power-fail deselect and write protect VOUT ECON LPSRAM 256 Kb to 16 Mb CE RESET R1 Microprocessor R2 VUNREG VPFI RST PFI Power-on reset/low-voltage detect Push-button reset reset Early power-fail warning 1.25 V RSTIN1 RSTIN2 11 NMI PFO Real-time clock section I/O 2/4 XTAL WDI 400 khz oscillator Day Century bits Calibration Alarm Square wave 44 Bytes NVRAM WDF AF IRQ/FT/OUT SQW IRQ ADDR/DATA BUS

12 Securitizor Combined real-time clock (RTC) IC including microprocessor supervisor, NVRAM supervisor, with physical tamper detect, plus internal and external RAM clear for secure applications. M41ST87W 64-bit unique serial number -40 to +85 C 3 V, 3.3 V, 5 V operation 500 na standby (typ) at 3.0 V 28-lead embedded crystal IC Counters for 10ths and 100ths of seconds, seconds, minutes, hours, day, date, month, year, and century 128 bytes of clearable NVRAM Programmable alarm with repeat modes functions in battery-backed mode Programmable square-wave output 1 Hz to Dedicated output NVRAM supervisor features switchover Power-fail write protect monitor Turns LPSRAM into NVRAM SOX28 Embedded crystal (internal view) Tamper circuit features Two independent inputs detect circuit opening or closing. Options on alarm: Generate interrupt Clear internal RAM Clear external RAM Store event time (always) Output reset Tamper detect functions even in batterybacked mode Oscillator fail detect bit indicates oscillator has slowed, and crystal may have been tampered SSOP20 Application examples 12 Black boxes Closed-circuit TV Financial security: ATM, cash, registers, POS, card readers Gaming machines Fire alarms Metering (gas, electricity, water) Microprocessor supervisor functions Programmable watchdog 62.5 ms to 128 s timeout period Power-on reset/low-voltage detect Two reset input pins Two independent early power-fail warning circuits (PFI/PFO) with 1.25 V precision reference M41ST87W application diagram TP1IN TP2IN Power-on reset/ low-voltage detect Early power-fail warning (PFI/PFO) Interrupt EXT RAM CLR INT RAM CLR Microprocessor/ Microcontroller /CE switchover Write protect LPSRAM VBAT Day Century bits Calibration Alarm Square wave 64 bit ser. no. 128 Bytes Nvram

13 Regulator VUNREG M41ST87W VOUT LPSRAM CE RESET Microprocessor NMI WDI R1 R2 VUNREG WDI VPFI PFO2 PFO1 2 TP1IN TP2IN XTAL VSS PFI1 VBAT PFI V REF EX RST 400 KHz interface oscillator Compare Compare Power-fail write protect Power-fail deselect and write protect monitor Debounce Real-time clock section /BL 128 bytes RAMCLR user ram WD Real-time clock with alarm AF Osc monitor OF Square wave 64 bit serial number TD1 Tamper ckt 1 TD2 Tamper ckt 2 (RESET ON W-DOG) ECON (RESET ON TPCLR) RSTIN1 RSTIN2 IRQ/OUT SQW TPCLR Any size Kbytes to 16 Mbytes CE 13 IRQ ADDR/DATA BUS Highly-integrated RTCs portfolio Part number M41ST85W M41ST87W Package supply current (Ibat) typ (na) NVRAM size (bytes) Data bus type V CC min - max (V) switchover Oscillator fail detect Programmable alarms Square wave dedicated output Power-up output frequency (khz) timer low detect Power on Reset/low voltage detector output SOX SOH SSOP SOX Power fail comparator Reset inputs Embedded crystal M41T94 Note: 1: 2 MHz 2: 400 khz 3: With IRQ output 4: Fixed switchover reference SO SPI SOH SPI

14 SERIAL REAL-TIME CLOCKS PORTFOLIO Part number Package Package size V CC min - max Ibat typ Timekeeping min NVRAM (mm) (V) (na) (V) (bytes) Oscillator fail detect M41T60 QFN16 3.0x M41T62 LCC8 QFN16 1.5x x M41T63 QFN16 3.0x M41T64 QFN16 3.0x Features Dedicated SQW output, crystal, I 2 C, programmable alarm, 32 khz, WDG Dedicated SQW and WDG timer output, crystal, I 2 C, programmable alarm, 32 khz Dedicated SQW output, I 2 C, programmable alarm, 32 khz, WDG M41T65 QFN16 3.0x Dedicated WDG timer output,, programmable alarm Dedicated SQW output, programmable alarm, M41T66 QFN16 3.0x khz, WDG, M41T0 SO-8 3.9x M41T00S SO-8 3.9x switchover with fixed reference, M41T00AUD DFN16 4.0x switchover with fixed reference, integrated audio amplifier, M41T00CAP PCDIP x switchover with fixed reference, integrated battery, I 2 C, crystal M41T11 SO-8 SOH x x switchover, SNAPHAT package available, M41T56 SO-8 3.9x M41T80 SO-8 3.9x switchover,, programmable alarm, SQW 14 M41T81 SO-8 3.9x M41T81S SO-8 SOX x x M41T82 SO-8 3.9x M41T83 M41T93 M41ST85W M41ST87W M41T94 QFN16 SOX-18 QFN16 SOX-18 SOH28 SOX-28 SOX-28 SSOP20 SO16 SOH28 4.0x x x x x x x x x x M41TC8025 S x switchover, low battery detection,, programmable alarm, SQW, WDG switchover with fixed reference, low battery detection, crystal,, programmable alarm, SQW, WDG Analog calibration, battery switchover with fixed reference, low battery detection,, POR/LVD Analog calibration, battery switchover with fixed reference, low battery detection,, programmable alarm, 32 khz, WDG, POR/LVD Analog calibration, battery switchover with fixed reference, low battery detection, crystal, 10 MHz SPI, programmable alarm, 32 khz, WDG, POR/LVD switchover with fixed reference, low battery detection, microprocessor supervisor functions, crystal, SNAPHAT package,, programmable alarm, SQW, WDG, POR/LVD, PFI/PFO, RSTin switchover with fixed reference, low battery detection, microprocessor supervisor functions, tamper detection,, programmable alarm, 32 khz, WDG, POR/LVD, PFI/PFO, RSTin switchover with fixed reference, low battery detection, microprocessor supervisor functions, snaphat package, 2 MHz SPI, programmable alarm, SQW, WDG, POR/LVD, RSTin Temperature compensated, Low battery detection,, programmable alarm, SQW, Fout 1 Hz-1 KHz-, POR/LVD

15 Glossary Function Timekeeping supply voltage Programmable alarms Square wave output (SQW) Oscillator fail detect Power-up output frequency (F32K) switchover (VSO) timer (WDG) low detect (BL) Power on reset/low voltage detector output (POR/LVD) Power fail comparator (PFI/PFO) Reset inputs (RSTin) Description Minimum oscillator operating voltage for specified temperature range. An alarm which can be set for a specified date and time, or to repeat at a certain day of every month, or at a certain hour of every day, or at a certain minute of every hour, or a certain second of every minute. A user programmable square wave signal with rail-to-rail amplitude and 50% duty cycle which is output on the SQW pin. A flag bit used to indicate that the oscillator has either stopped, or was stopped for some period of time and can be used to judge the validity of the clock and date data. A special 32 khz square wave function which is enabled on power-up to output on the F32K pin. Some devices offer this power-up default signal on the SQW pin. The voltage threshold at which the device power is switched to the back-up battery supply when V CC falls. At this time the clock registers is maintained by the attached battery supply. As system power returns and V CC rises above VSO, the battery is disconnected, and the power supply is switched to external V CC. The watchdog timer is used to detect an out-of-control microprocessor. The user programs the watchdog timer by setting the desired amount of time-out into the watchdog register. low detect is an automatic comparison of the battery voltage with a reference voltage of ~2.5 V. If the battery voltage is found to be less than 2.5 V, a flag is set and clock data should be considered suspect and verified as correct. A fresh battery should be installed. A continuous monitor of the V CC supply. When V CC falls to the power fail detect threshold, the /RST output pulls low and remains low for a defined recovery time after power-up, This function is intended for use as an early warning undervoltage detector to signal a failing power supply. Independent inputs which can generate an output reset which is identical to a reset generated by a power cycle. Package options LCC8 1.5 mm x 3.2 mm Embedded crystal QFN16 3 mm x 3 mm QFN16 4 mm x 4 mm DFN16 5 mm x 4 mm SO mm x 4.80 mm SO mm x 5.3 mm Embedded crystal SO mm x 9.80 mm 15 SNAPHAT : and crystal snap on module to order separately (internal view) SSOP mm x 5.3 mm PCDIP24 CAPHAT mm x mm Self-contained battery and crystal (internal view) SOX mm x 7.62 mm Embedded crystal SOIC SOX mm x 7.67 mm Embedded crystal SOH mm x 8.23 mm SNAPHAT packaging Serial real-time clocks are packaged in a special SNAPHAT SOIC which mates with ST s SNAPHAT battery/crystal top. The SNAPHAT top can be removed and replaced allowing the user to extend the battery backup time indefinitely. SNAPHAT tops, battery and crystal integrated 48 mah 120 mah M4T28-BR12SH M4T32-BR12SH Embedded crystal packaging The crystal is encapsulated in the serial real-time clock IC package. This allows the crystal to be less sensitive to humidity, temperature and vibration with the benefit of being a surface mount solution. It also enhances security by shielding the crystal from tampering. SOX28 Embedded crystal (internal view) SOX18 Embedde crystal (internal view)

16 Design support Real-time clocks application notes, technical notes, online calculators and resources Readers will find these documents helpful in understanding some of the subtleties of RTCs and what it takes to keep them running reliably. AN922 AN923 AN1011 AN934 AN1012 AN1879 AN1572 AN2583 AN2678 AN2971 AN3060 TA0344 Application notes Using a super cap to back up the M41T56, M41T00, M41T11, M41T81, M41T94 and M41ST84W (16-pin) Timekeeper rolling into the year 2000 (21st century, Y2K) technology used in NVRAM and real-time clock (RTC) products from ST How to use the digital calibration feature in Timekeeper and serial real-time clock (RTC) products Predicting the battery life and data retention period of NVRAMs and serial RTCs How to use M41ST87 tamper detect and RAM clear Power-down time-stamp function in serial real-time clocks (RTCs) Understanding and applying the M41T00AUD real-time clock with audio Extremely accurate timekeeping over temperature using adaptive calibration Using the typical temperature characteristics of crystal to compensate the M41T83 and the M41T93 serial real-time clocks Applications guide for serial real-time clocks (RTCs) Technical note Highly accurate, automatic temperature-compensated real-time clock (RTC) solution Product support at Datasheets Application notes Selector tables Serial RTC example code UL information Clock calibration tools RTC and NVRAM model files Design support Online technical support STMicroelectronics - December Printed in United Kingdom - All rights reserved The STMicroelectronics corporate logo is a registered trademark of the STMicroelectronics group of companies All other names are the property of their respective owners Order code: BRRTC1212 For more information on ST products and solutions, visit

Microprocessor resets and supervisor ICs

Microprocessor resets and supervisor ICs Selection guide Microprocessor resets and supervisors Microprocessor supervisors with switchover December 2005 www.st.com/supervisor www.st.com/reset www.st.com/rtc