APPLICATION NOTES A V A I L A B L E X25043/45AN11 • AN21 X25043/45 4K 512 x 8 Bit Programmable Watchdog Supervisory E2PROM FEATURES DESCRIPTION • • • • • The X25043/45 combines three popular functions, Watchdog Timer, Voltage Supervision, and E2PROM in a single package. This combination lowers the system cost and reduces the board space requirements. • • • • • • • • Programmable Watchdog Timer Low VCC Detection Reset Signal Valid to VCC = 1V 1MHz Clock Rate 512 X 8 Bits Serial E2PROM —4 Byte Page Mode Low Power CMOS —50µA Standby Current —3mA Active Current 2.7V To 5.5V Power Supply Block LockTM —Protect 1/4, 1/2 or all of E2PROM Array Built-in Inadvertent Write Protection —Power-Up/Power-Down protection circuitry —Write Latch —Write Protect Pin High Reliability —Endurance: 100,000 cycles per byte —Data Retention: 100 Years —ESD protection: 2000V on all pins Available Packages —8-Lead PDlP —8-Lead SOIC —14-Lead TSSOP X25043 = Active LOW RESET X25045 = Active HIGH RESET The Watchdog Timer provides an independent protection system for microcontrollers. During a system failure, the X25043/45 watchdog will respond with a RESET/ RESET signal after a selectable time-out interval. The user selects the interval from three preset values. Once selected, the interval does not change, even after cycling the power. The system is protected from low voltage conditions by the X25043/45 low VCC detection circuits. When VCC drops below the minimum VCC trip point, the system is reset. Reset is asserted until VCC returns and stabilizes. The memory portion of the X25043/45 is a CMOS 4096bit serial E2PROM, internally organized as 512 X 8. The X25043/45 features a Serial Peripheral Interface (SPI) and software protocol allowing operation on a simple three-wire bus. The X25043/45 utilizes Xicor’s proprietary Direct Write™ cell, providing a minimum endurance of 100,000 cycles per byte and a minimum data retention of 100 years. DIE PHOTOGRAPH RESET CONTROL LOGIC SERIAL INTERFACE LOGIC PROGRAMMABLE VOLTAGE SENSOR 4K BITS E22PROM W A T T I C M H E D R O G HIGH HIGH VOLTAGE VOLTAGE GENERATOR GENERATOR AND AND CONTROL CONTROL 3844 ILL F01 Direct Write™ is a trademark of Xicor, Inc. ©Xicor, Inc. 1994, 1995, 1996 Patents Pending 3844-6.5 5/9/96 T4/C2/D2 NS 1 Characteristics subject to change without notice X25043/45 PIN CONFIGURATION PIN DESCRIPTIONS Serial Output (SO) X25043/45 SO is a push/pull serial data output pin. During a read cycle, data is shifted out on this pin. Data is clocked out by the falling edge of the serial clock. 8-LEAD DIP/SOIC Serial Input (SI) SI is the serial data input pin. All opcodes, byte addresses, and data to be written to the memory are input on this pin. Data is latched by the rising edge of the serial clock. CS 1 8 VCC SO 2 7 RESET/RESET WP 3 6 SCK VSS 4 5 SI X25043/45 14-LEAD TSSOP Serial Clock (SCK) The Serial Clock controls the serial bus timing for data input and output. Opcodes, addresses, or data present on the SI pin is latched on the rising edge of the clock input, while data on the SO pin changes after the falling edge of the clock input. Chip Select (CS) When CS is HIGH, the X25043/45 is deselected and the SO output pin is at high impedance and, unless an internal write operation is underway, the X25043/45 will be in the standby power mode. CS LOW enables the X25043/45, placing it in the active power mode. It should be noted that after power-up, a HIGH to LOW transition on CS is required prior to the start of any operation. CS 1 14 VCC SO 2 13 RESET/RESET NC 3 12 NC NC 4 11 NC NC 5 10 NC WP 6 9 SCK VSS 7 8 SI 3844 ILL F02.3 PIN NAMES Symbol CS SO SI SCK WP VSS VCC RESET/RESET Write Protect (WP) When WP is LOW, nonvolatile writes to the X25043/45 are disabled, but the part otherwise functions normally. When WP is held HIGH, all functions, including nonvolatile writes operate normally. WP going LOW while CS is still LOW will interrupt a write to the X25043/45. If the internal write cycle has already been initiated, WP going LOW will have no affect on a write. Reset (RESET, RESET) Description Chip Select Input Serial Output Serial Input Serial Clock Input Write Protect Input Ground Supply Voltage Reset Output 3844 PGM T01.1 X25043/45, RESET/RESET is an active LOW/HIGH, open drain output which goes active whenever VCC falls below the mimimum VCC sense level. It will remain active until VCC rises above the minimum VCC sense level for 200ms. RESET/RESET also goes active if the Watchdog timer is enabled and CS remains either HIGH or LOW longer than the Watchdog time-out period. A falling edge of CS will reset the watchdog timer. 2 X25043/45 PRINCIPLES OF OPERATION The Write-In-Process (WIP) bit indicates whether the X25043/45 is busy with a write operation. When set to a “1”, a write is in progress, when set to a “0”, no write is in progress. During a write, all other bits are set to “1”. The WIP bit is read-only. E2PROM The X25043/45 is a 512 x 8 designed to interface directly with the synchronous serial peripheral interface (SPI) of many popular microcontroller families. The X25043/45 contains an 8-bit instruction register. It is accessed via the SI input, with data being clocked in on the rising SCK. CS must be LOW and WP input must be HIGH during the entire operation. The X25043/45 monitors the bus and provides a RESET/RESET output if there is no bus activity within the preset time period. The Write Enable Latch (WEL) bit indicates the status of the “write enable” latch. When set to a “1”, the latch is set, when set to a “0”, the latch is reset. The WEL bit is readonly and is set by the WREN instruction and reset by WRDI instruction or successful completion of a write cycle. Table 1 contains a list of the instructions and their operation codes. All instructions, addresses and data are transferred MSB first. Bit 3 of the Read and Write instructions contain the higher order address bit, A8. The Block Protect (BL0 and BL1) bits indicate the extent of protection employed. These nonvolatile bits are set by issuing the WRSR instruction and allows the user to select one of four levels of protection and program the watchdog timer. The X25043/45 is divided into four 1024-bit segments. One, two, or all four of the segments may be locked. That is, the user may read the segments but will be unable to alter (write) data within the selected segments. The partitioning is controlled as illustrated below with the state of BL1 and BL0. Data input is sampled on the first rising edge of SCK after CS goes LOW. SCK is static, allowing the user to stop the clock and then resume operations. Write Enable Latch The X25043/45 contains a “write enable” latch. This latch must be SET before a write operation will be completed internally. The WREN instruction will set the latch and the WRDI instruction will reset the latch. This latch is automatically reset upon a power-up condition and after the completion of a byte, page, or status register write cycle. The latch is also reset if WP is brought LOW. Status Register Bits BL1 BL0 0 0 1 1 0 1 0 1 Status Register 6 5 4 X WD1 WD0 None $180–$1FF $100–$1FF $000–$1FF 3844 PGM T04 The RDSR instruction provides access to the status register. The status register may be read at any time, even during a write cycle. The status register is formatted as follows: 7 X Array Addresses Protected 3 BL1 2 BL0 1 WEL The Watchdog Timer (WD0 and WD1) bits allow setting of the watchdog time-out function as shown in the table below. These nonvolatile bits are set by issuing the WRSR instruction. 0 WIP Status Register Bits WD1 WD0 3844 PGM T02 0 0 1 1 When issuing, WREN, WRDI and RDSR commands, it is not necessary to send a byte address or data. 0 1 0 1 Watchdog Time-out (Typical) 1.4 Seconds 600 Milliseconds 200 Milliseconds Disabled 3844 PGM T03 3 X25043/45 transmitted, CS must then be taken HIGH. If the user continues the write operation without taking CS HIGH after issuing the WREN instruction the write operation will be ignored. Clock and Data Timing Data input on the SI line is latched on the rising edge of SCK. Data is output on the SO line by the falling edge of SCK. To write data to the E2PROM memory array, the user issues the WRITE instruction, followed by the address and then the data to be written. Bit 3 of the Write instruction contains address A8. This bit is used to select the upper or lower half of the device. This is minimally a twenty-four clock operation. CS must go LOW and remain LOW for the duration of the operation. The host may continue to write up to four bytes of data to the X25043/45. The only restriction is the four bytes must reside on the same page. A page address begins with address X XXXX XX00 and ends with X XXXX XX11. If the byte address counter reaches X XXXX XX11 and the clock continues the counter will roll back to the first address of the page and overwrite any data that may have been written. Read Sequence When reading from the E2PROM memory array, CS is first pulled LOW to select the device. The 8-bit READ instruction is transmitted to the X25043/45, followed by the 8-bit byte address. Bit 3 of the Read instruction contains address A8. This bit is used to select the upper or lower half of the device. After the read opcode and byte address are sent, the data stored in the memory at the selected address is shifted out on the SO line. The data stored in memory at the next address can be read sequentially by continuing to provide clock pulses. The byte address is automatically incremented to the next higher address after each byte of data is shifted out. When the highest address is reached ($1FF) the address counter rolls over to address $000, allowing the read cycle to be continued indefinitely. The read operation is terminated by taking CS HIGH. Refer to the read E2PROM Array operation sequence illustrated in Figure 1. For the write operation (byte or page write) to be completed, CS can only be brought HIGH after the twenty-fourth, thirty-second, fortieth, or forty-eighth clock. If it is brought HIGH at any other time, the write operation will not be completed. Refer to Figure 4 and 5 below for a detailed illustration of the write sequences. To read the status register the CS line is first pulled LOW to select the device followed by the 8-bit RDSR instruction. After the read status register opcode is sent, the contents of the status register is shifted out on the SO line as shown in Figure 2. While the write is in progress, following a status register or E2PROM write sequence the status register may be read to check the WIP bit. During this time the WIP bit will be HIGH and all other bits in the status register will be undefined. Write Sequence Prior to any attempt to write data into the X25043/45 the “write enable” latch must first be set by issuing the WREN instruction (See Figure 3). CS is first taken LOW, then the WREN instruction is clocked into the X25043/45. After all eight bits of the instruction are RESET/RESET Operation The RESET (X25043) output is designed to go LOW whenever VCC has dropped below the minimum trip point and/or the Watchdog timer has reached its programmable time-out limit. Table 1. Instruction Set Instruction Name WREN WRDI RDSR WRSR Instruction Format* 0000 0110 0000 0100 0000 0101 0000 0001 READ 0000 A8011 WRITE 0000 A8010 Operation Set the Write Enable Latch (Enable Write Operations) Reset the Write Enable Latch (Disable Write Operations) Read Status Register Write Status Register (Block Lock Bits) Read Data from Memory Array beginning at selected address Write Data to Memory Array beginning at Selected Address (1 to 4 Bytes) 3844 PGM T05.1 *Instructions are shown MSB in leftmost position. Instructions are transferred MSB first. 4 X25043/45 The RESET (X25045) output is designed to go HIGH whenever VCC has dropped below the minimum trip point and/or the watchdog timer has reached its programmable time-out limit. Data Protection Operational Notes • A WREN instruction must be issued to set the “write enable” latch. The following circuitry has been included to prevent inadvertent writes: • The “write enable” latch is reset upon power-up. The X25043/45 powers-up in the following state: • CS must come HIGH at the proper clock count in order to start a write cycle. • The device is in the low power standby state. • A HIGH to LOW transition on CS is required to enter an active state and receive an instruction. The “write enable” latch is reset when WP is brought LOW. • SO pin is high impedance. • The “write enable” latch is reset. Figure 1. Read E2PROM Array Operation Sequence CS 0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 SCK INSTRUCTION BYTE ADDRESS 8 SI 7 6 5 4 3 2 1 0 9TH BIT OF ADDRESS DATA OUT HIGH IMPEDANCE 7 SO 6 5 4 3 2 1 0 MSB 3844 FHD F04 Figure 2. Read Status Register Operation Sequence CS 0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 SCK INSTRUCTION SI DATA OUT HIGH IMPEDANCE 7 SO MSB 5 6 5 4 3 2 1 0 3844 ILL F15 X25043/45 Figure 3. Write Enable Latch Sequence CS 0 1 2 3 4 5 6 7 SCK SI HIGH IMPEDANCE SO 3844 FHD F05 Figure 4. Byte Write Operation Sequence CS 0 1 2 3 4 5 6 7 8 9 7 6 10 11 12 13 14 15 16 17 18 19 20 21 22 23 SCK INSTRUCTION 8 SI DATA BYTE BYTE ADDRESS 5 4 3 2 1 0 7 6 5 4 3 2 1 0 9TH BIT OF ADDRESS HIGH IMPEDANCE SO 3844 FHD F06 SYMBOL TABLE WAVEFORM 6 INPUTS OUTPUTS Must be steady Will be steady May change from LOW to HIGH Will change from LOW to HIGH May change from HIGH to LOW Will change from HIGH to LOW Don’t Care: Changes Allowed N/A Changing: State Not Known Center Line is High Impedance X25043/45 Figure 5. Page Write Operation Sequence CS 0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 SCK INSTRUCTION SI DATA BYTE 1 BYTE ADDRESS 7 8 6 5 4 3 2 1 7 0 6 5 4 3 2 1 0 9TH BIT OF ADDRESS CS 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 SCK DATA BYTE 2 SI 7 6 5 4 3 2 DATA BYTE 3 1 0 7 6 5 4 3 2 DATA BYTE 4 1 0 7 6 5 4 3 2 1 0 3844 FHD F07 Figure 6. Write Status Register Operation Sequence CS 0 1 2 3 4 5 6 7 8 9 7 6 10 11 12 13 14 15 SCK DATA BYTE INSTRUCTION SI 5 4 3 2 1 0 HIGH IMPEDANCE SO 3844 ILL F08 7 X25043/45 ABSOLUTE MAXIMUM RATINGS* Temperature under Bias .................. –65°C to +135°C Storage Temperature ....................... –65°C to +150°C Voltage on any Pin with Respect to VSS ...... –1.0V to +7V D.C. Output Current ............................................. 5mA Lead Temperature (Soldering, 10 seconds) .............................. 300°C *COMMENT Stresses above those listed under “Absolute Maximum Ratings” may cause permanent damage to the device. This is a stress rating only and the functional operation of the device at these or any other conditions above those listed in the operational sections of this specification is not implied. Exposure to absolute maximum rating conditions for extended periods may affect device reliability. RECOMMENDED OPERATING CONDITIONS Temp Commercial Industrial Min. 0°C –40°C Supply Voltage X25043/45 X25043/45-2.7 Max. 70°C +85°C Limits 5V ±10% 2.7 to 5.5V 3844 PGM T07.3 3844 PGM T06.1 D.C. OPERATING CHARACTERISTICS (Over the recommended operating conditions unless otherwise specified.) Limits Symbol Parameter ICC VCC Supply Current (Active) Min. Max. 3 Units mA Test Conditions SCK = VCC x 0.1/VCC x 0.9 @ 1MHz, SO = Open ISB1 VCC Standby Current 50 µA CS = VCC, VIN = VSS or VCC, VCC = 5.5 ISB2 VCC Standby Current 20 µA CS = VCC, VIN = VSS or VCC, VCC = 2.7V ILI Input Leakage Current 10 µA VIN = VSS to VCC ILO Output Leakage Current 10 µA VOUT = VSS to VCC VIL(1) VIH(1) Input LOW Voltage VCC x 0.3 V VCC x 0.7 VCC + 0.5 V VOL Output LOW Voltage VOH1 Output HIGH Voltage VOH2 Output HIGH Voltage Input HIGH Voltage –0.5 0.4 V IOL = 2mA VCC–0.8 V IOH = –1.6mA, VCC = 4.5V VCC–0.4 V IOH = –.4mA, VCC = 2.7V V IOL = 1mA VOLRS Reset Output LOW Voltage 0.4 3844 PGM T08.3 POWER-UP TIMING Symbol tPUR(2) Parameter Power-up to Read Operation tPUW(2) Power-up to Write Operation Min. Max. 1 Units ms 5 ms 3844 PGM T09 CAPACITANCE TA = +25°C, f = 1MHz, VCC = 5V. Symbol COUT (2) CIN(2) Notes: Test Max. Units Conditions Output Capacitance (SO, RESET, RESET) 8 pF VOUT = 0V Input Capacitance (SCK, SI, CS, WP) 6 pF VIN = 0V (1) VIL min. and VIH max. are for reference only and are not tested. (2) This parameter is periodically sampled and not 100% tested. 8 3844 PGM T10.2 X25043/45 EQUIVALENT A.C. LOAD CIRCUIT AT 5V VCC A.C. TEST CONDITIONS Input Pulse Levels VCC x 0.1 to VCC x 0.9 Input Rise and Fall Times 10ns Input and Output Timing Level VCC x 0.5 5V 5V 4.6KΩ OUTPUT 3844 PGM T11 RESET/RESET 100pF 100pF 3844 FHD F12.2 A.C. CHARACTERISTICS (Over recommended operating conditions, unless otherwise specified) Data Input Timing Symbol fSCK tCYC tLEAD tLAG tWH tWL tSU tH tRI(3) tFI(3) tCS tWC(4) Parameter Clock Frequency Cycle Time CS Lead Time CS Lag Time Clock HIGH Time Clock LOW Time Data Setup Time Data Hold Time Input Rise Time Input Fall Time CS Deselect Time Write Cycle Time Min. Max. Units 0 1000 500 500 500 400 100 100 1 MHz ns ns ns ns ns ns ns µs µs ns ms 2 2 500 10 3844 PGM T12.2 Data Output Timing Symbol fSCK tDIS tV tHO tRO(3) tFO(3) Parameter Min. Max. Units Clock Frequency Output Disable Time Output Valid from Clock LOW Output Hold Time Output Rise Time Output Fall Time 0 1 500 400 MHz ns ns ns ns ns 0 300 300 3844 PGM T13.1 Notes: (3) This parameter is periodically sampled and not 100% tested. (4) tWC is the time from the rising edge of CS after a valid write sequence has been sent to the end of the self-timed internal nonvolatile write cycle. 9 X25043/45 Serial Output Timing CS tCYC tWH tLAG SCK tV SO SI tHO MSB OUT tWL tDIS MSB–1 OUT LSB OUT ADDR LSB IN 3844 FHD F09 Serial Input Timing tCS CS tLEAD tLAG SCK tSU SI tH tRI MSB IN tFI LSB IN HIGH IMPEDANCE SO 3844 FHD F10 10 X25043/45 Power-Up and Power-Down Timing VTRIP VCC VTRIP tPURST 0 Volts tPURST tF tRPD tR RESET (X25043) RESET (X25045) 3844 FHD F13.1 RESET Output Timing Symbol VTRIP tPURST tRPD(5) tF(5) tR(5) VRVALID Parameter Min. Reset Trip Point Voltage, 5V Device Reset Trip Point Voltage, 2.7V Device Power-up Reset Timeout VCC Detect to Reset/Output VCC Fall Time VCC Rise Time Reset Valid VCC Typ. 4.25 2.55 100 Max. Units 4.5 2.7 400 500 V V ms ns µs ns V 10 0 1 3844 PGM T14.3 Notes: (5) This parameter is periodically sampled and not 100% tested. CS vs RESET/RESET Timing CS tCST RESET tWDO tRST tWDO tRST RESET 3844 FHD F14.1 RESET/RESET Output Timing Symbol tWDO tCST tRST Parameter Watchdog Timeout Period, WD1=1,WD0=0 WD1=0,WD0=1 WD1=0,WD0=0 CS Pulse Width to Reset the Watchdog Reset Timeout Min. Typ. Max. Units 100 450 1 400 100 200 600 1.4 300 800 2 ms ms sec ns ms 400 3844 PGM T15.3 11 X25043/45 PACKAGING INFORMATION 8-LEAD PLASTIC DUAL IN-LINE PACKAGE TYPE P 0.430 (10.92) 0.360 (9.14) 0.260 (6.60) 0.240 (6.10) PIN 1 INDEX PIN 1 0.300 (7.62) REF. HALF SHOULDER WIDTH ON ALL END PINS OPTIONAL 0.145 (3.68) 0.128 (3.25) SEATING PLANE 0.025 (0.64) 0.015 (0.38) 0.065 (1.65) 0.045 (1.14) 0.150 (3.81) 0.125 (3.18) 0.020 (0.51) 0.016 (0.41) 0.110 (2.79) 0.090 (2.29) 0.015 (0.38) MAX. 0.060 (1.52) 0.020 (0.51) 0.325 (8.25) 0.300 (7.62) 0° 15° TYP. 0.010 (0.25) NOTE: 1. ALL DIMENSIONS IN INCHES (IN PARENTHESES IN MILLIMETERS) 2. PACKAGE DIMENSIONS EXCLUDE MOLDING FLASH 12 X25043/45 PACKAGING INFORMATION 8-LEAD PLASTIC SMALL OUTLINE GULL WING PACKAGE TYPE S 0.150 (3.80) 0.158 (4.00) 0.228 (5.80) 0.244 (6.20) PIN 1 INDEX PIN 1 0.014 (0.35) 0.019 (0.49) 0.188 (4.78) 0.197 (5.00) (4X) 7° 0.053 (1.35) 0.069 (1.75) 0.004 (0.19) 0.010 (0.25) 0.050 (1.27) 0.010 (0.25) X 45° 0.020 (0.50) 0.050" TYPICAL 0.050" TYPICAL 0° – 8° 0.0075 (0.19) 0.010 (0.25) 0.250" 0.016 (0.410) 0.037 (0.937) FOOTPRINT NOTE: ALL DIMENSIONS IN INCHES (IN PARENTHESES IN MILLIMETERS) 13 0.030" TYPICAL 8 PLACES X25043/45 PACKAGING INFORMATION 14-LEAD PLASTIC, TSSOP PACKAGE TYPE V .025 (.65) BSC .169 (4.3) .252 (6.4) BSC .177 (4.5) .193 (4.9) .200 (5.1) .047 (1.20) .0075 (.19) .0118 (.30) .002 (.05) .006 (.15) .010 (.25) Gage Plane 0° – 8° Seating Plane .019 (.50) .029 (.75) Detail A (20X) .031 (.80) .041 (1.05) See Detail “A” NOTE: ALL DIMENSIONS IN INCHES (IN PARENTHESES IN MILLIMETERS) 3926 FHD F32 14 X25043/45 ORDERING INFORMATION X25043/45 P T -V VCC Limits Blank = 5V ±10% 2.7 = 2.7V to 5.5V Device Temperature Range Blank = Commercial = 0°C to +70°C I = Industrial = –40°C to +85°C Package P = 8-Lead Plastic DIP S = 8-Lead SOIC V = 14-Lead TSSOP Part Mark Convention X25043/45 Blank = 8-Lead SOIC P = 8-Lead Plastic DIP V = 14-Lead TSSOP X X Blank = 5V ±10%, 0°C to +70°C I = 5V ±10%, –40°C to +85°C F = 2.7V to 5.5V, 0°C to +70°C G = 2.7V to 5.5V, –40°C to +85°C LIMITED WARRANTY Devices sold by Xicor, Inc. are covered by the warranty and patent indemnification provisions appearing in its Terms of Sale only. Xicor, Inc. makes no warranty, express, statutory, implied, or by description regarding the information set forth herein or regarding the freedom of the described devices from patent infringement. Xicor, Inc. makes no warranty of merchantability or fitness for any purpose. Xicor, Inc. reserves the right to discontinue production and change specifications and prices at any time and without notice. Xicor, Inc. assumes no responsibility for the use of any circuitry other than circuitry embodied in a Xicor, Inc. product. No other circuits, patents, licenses are implied. U.S. PATENTS Xicor products are covered by one or more of the following U.S. Patents: 4,263,664; 4,274,012; 4,300,212; 4,314,265; 4,326,134; 4,393,481; 4,404,475; 4,450,402; 4,486,769; 4,488,060; 4,520,461; 4,533,846; 4,599,706; 4,617,652; 4,668,932; 4,752,912; 4,829, 482; 4,874, 967; 4,883, 976. Foreign patents and additional patents pending. LIFE RELATED POLICY In situations where semiconductor component failure may endanger life, system designers using this product should design the system with appropriate error detection and correction, redundancy and back-up features to prevent such an occurrence. Xicor's products are not authorized for use in critical components in life support devices or systems. 1. Life support devices or systems are devices or systems which, (a) are intended for surgical implant into the body, or (b) support or sustain life, and whose failure to perform, when properly used in accordance with instructions for use provided in the labeling, can be reasonably expected to result in a significant injury to the user. 2. A critical component is any component of a life support device or system whose failure to perform can be reasonably expected to cause the failure of the life support device or system, or to affect its safety or effectiveness. 15