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SILICON SENSING Proprietary

CRS10 Digital Rate Gyro Product Specification

Document No: Issue: Date DCR No.

CRS10-01-0100-121 3 November 2007 614663

SILICON SENSING Proprietary

CRS10 Digital Rate Gyro

SILICON SENSING Proprietary This is an unpublished work created in 2007, any copyright in which vests in SILICON SENSING. All rights reserved. The information contained in this document is proprietary to SILICON SENSING unless stated otherwise and is made available in confidence; it must not be used or disclosed without the express written permission of SILICON SENSING. This document may not be copied in whole or in part in any form without the express written consent of SILICON SENSING which may be given by contract. This document contains trade secrets and/or sensitive commercial and/or financial information as of the date provided to the original recipient by SILICON SENSING and is provided in confidence. Release of the information to any third party is prohibited without prior written consent from SILICON SENSING. Public authorities are prohibited from releasing the information unless its release would not constitute an actionable breach of confidence. Public authorities should contact SILICON SENSING to determine the current releasability of the information. [5 USC 552(b)(4) and 18 USC 1905]/ [Sections 41 and 43 of the Freedom of Information Act 2000] are applicable. UK Origin Any enquiries relating to this document or its contents should be addressed in the first instance to: SILICON SENSING, Clittaford Road, Southway, Plymouth, Devon PL6 6DE Telephone: (01752) 723330 Fax: (01752) 723331 International: International: +44 1752 723330 +44 1752 723331

SILICON SENSING and the

wordmark are trademarks of SILICON SENSING.

CRS10 Digital Rate Gyro

CRS10-01-0100-121 Rev 3

CRS10 Digital Rate Gyro

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CRS10 Digital Rate Gyro

CRS10-01-0100-121 Rev 3

CRS10 Digital Rate Gyro

ORDERING INFORMATION

Model CRS10-01 Bandwidth 75 Hz (user programmable) Digital Rate Range ±300°/s Analogue Rate Range ±75°/s (user programmable)

GENERAL DESCRIPTION FEATURES

· · · · · · · · · · · · · · · · Digital Angular Rate Gyroscope Suitable for High integrity applications Wide temperature range operation High Bandwidth and rate range Very low Angular Random Walk High vibration rejection over wide frequency 1000 g-powered shock survivability 5 V single-supply operation 23 mm × 17 mm × 10 mm package SPI® compatible digital output interface Absolute rate output for precision applications Ratiometric analogue rate output Out of plane Z-axis (yaw) rate response Externally controlled self-test (CBIT) Internal temperature sensor output RoHS compliant The CRS10 Rate Sensor incorporates the Silicon Sensing Micro-Machined Silicon Ring and a micro controller to make a functionally complete digital angular rate sensor with an integrated serial peripheral interface (SPI). The CRS10-01 default configuration is a 75Hz bandwidth, ±300°/s digital rate sensor with a ±75°/s analogue rate range. Other rate ranges and bandwidths can be programmed by the user (bandwidths available are 5Hz, 10Hz, 25Hz, 40Hz, 50Hz, 60Hz 75Hz and 100Hz).

® The digital rate data available at the SPI port is proportional to the angular rate about the axis that is normal to the mounting surface of the package (see Figure 9).

Other SPI messages can be accessed containing a range of other data if required. If the basic uncompensated performance is insufficient for your application, access to an internal temperature sensor is provided. This enables individual temperature modelling and compensation. The CRS10 has been developed to produce stable bias performance over a wide operating temperature range. An internal continuous BIT function (BIT) and externally commanded test function (CBIT) are provided, which together test the complete operation of the sensor and the integrity of the signal-conditioning circuits. The CRS10 is available in a 23 mm × 17 mm × 10 mm package and is also available with either a Vertical or Horizontal bracket which can be surface mounted on a PCB (consult factory for further information)

APPLICATIONS

· · · · · · Automotive Yaw rate measurement Guidance and control Platform stabilization Image stabilization Inertia measurement units Robotics

FUNCTIONAL BLOCK DIAGRAM

Figure 1

CRS10 Digital Rate Gyro

CRS10-01-0100-121 Rev 3

CRS10 Digital Rate Gyro

TABLE OF CONTENTS

TABLE OF CONTENTS .............................................................5 ABSOLUTE MAXIMUM RATINGS *...........................................6 NORMAL OPERATING RATINGS .............................................6 ESD SENSITIVITY .....................................................................6 SPECIFICATIONS .....................................................................6 PIN DIAGRAM............................................................................8 CRS10 PIN DESCRIPTIONS .....................................................8 THEORY OF OPERATION ........................................................9

PRINCIPLE ........................................................................................9 IMPLEMENTATION ...........................................................................9 ANALOGUE RATE OUTPUT CHANNEL.........................................12

USER PROGRAM NOTES ......................................................13 MECHANICAL DESIGN ...........................................................14

PACKAGE OUTLINE DIMENSIONS................................................14 RECOMMENDED SOLDER CONDITIONS FOR THE VERTICAL OR HORIZONTAL BRACKET ................................................................14

CRS10 MEAN TIME BEFORE FAILURE (MTBF) CALCULATIONS......................................................................15

SELF-TEST FUNCTION.............................................................9 SPI CONFIGURATION ON POWER UP....................................9 SERIAL PERIPHERAL INTERFACE PORT.............................10 EXTERNAL SYSTEM TO CRS10 MESSAGES .......................10 EXTERNAL INTERFACE DISCRETE SIGNALS......................11

RESET_IN (INPUT) .........................................................................11

.

CRS10 Digital Rate Gyro

CRS10-01-0100-121 Rev 3

CRS10 Digital Rate Gyro

ABSOLUTE MAXIMUM RATINGS *

Operating Temperature Storage Temperature Maximum Operating Voltage Maximum Current on Start-up Ripple Operation (full operation) Power Supply Ripple -40ºC to +125ºC -55ºC to +140ºC 6.0V 75mA <5mV in frequency range 100 Hz to 12 kHz <2mV in frequency range 12 kHz to 400 MHz At the resonator frequency 13.4 kHz to 14.6 kHz the power supply ripple should not exceed 0.5mV pk-pk and at the third harmonic frequency (40.5 kHz to 43.5 kHz) the power supply ripple should not exceed 0.5mV pk-pk 6 V for 1 second with a current limit of < 100 mA

Reverse Power Supply Protection

NOTE *: Stresses beyond those listed under "Absolute Maximum Ratings" may cause permanent damage to the device. These are stress ratings only and functional operation of the device at these or other conditions beyond those indicated is not implied.

NORMAL OPERATING RATINGS

Operating Temperature Supply Voltage Supply Current -40ºC to +125ºC 5V dc nominal, (4.75V min, 5.25 max continuous) 60mA maximum @ 5.25V across operating temperature

ESD SENSITIVITY

The CRS10 device is rated to 2kV using the Human Body Model (direct contact, 100pF/1.5kOhm). ESD (Electrostatic Discharge) sensitive device Charged devices and circuit boards can discharge without detection. Although this product features patented or proprietary protection circuitry, damage may occur on devices subjected to high energy ESD. Therefore, proper ESD precautions should be taken to avoid performance degradation or loss of functionality.

SPECIFICATIONS

Ambient Temperature (TA) = -40ºC to 125ºC, VDD = 4.75V to 5.25V, Angular Rate = 0°/s, unless otherwise stated.

Table 1 Parameters Scale Factor Analogue Full Scale Range (Default) Scale Factor Analogue (Default) Digital Full Scale Range Scale Factor (digital) Nominal Scale Factor Initial setting Scale Factor Variation with temperature Scale Factor Rate Non Linearity Bias Bias Initial Setting - Digital Bias Initial Setting - Analogue Bias Variation with temperature Bias Instability Ratiometric Error (analogue) g sensitivity (±10 g range) Cross Coupling Errors Cross axis sensitivity Dynamic response Gain Peaking Bandwidth Noise From 1Hz to 75Hz band Broadband noise Angular random walk CRS10 Digital Rate Gyro Conditions Units Value

1

Ratiometric wrt VDD

TA = 25°C

°/s mV/°/s °/s lsb/°/s % % % Full Scale

±75 24 ±300 32 ±1 ±2 0.25

TA = 25°C TA = 25°C Ratiometric wrt VDD

°/s °/s °/s °/hr °/s °/s/g

±1 ±1 ±3 4 12 ±1 ±0.01

%

< 2.5

wrt 1Hz -3dB wrt 1Hz

dB Hz

<1 > 75Hz

°/s rms °/s rms °/hr

<0.5 <1.5 4 <5 CRS10-01-0100-121 Rev 3

CRS10 Digital Rate Gyro

Parameters Commanded BIT (CBITA) Nominal rate output offset Offset variation/tolerance Max data loss during test Power Supply VDD VDD Quiescent Supply Current Environment Temperature Linear Acceleration Shock Vibration Mass Conditions Units Value

1

TA = 25°C Bandwidth dependant

°/s °/s ms

+25.0 ±3 500

VDD= 5.25 V

V mA

+5 ±0.25 60

2

Steady state, any axis. ½ sine, t = 1 ms, recovery within 20 ms 20 Hz to 2 kHz

°C g g g rms grams

-40 to +125 10 95 min 8.85 <10

1 2

Unless otherwise stated errors quoted in this table refer to the digital rate output.

Operating Voltage stated as 4.75V to 5.25V (5V optimum). Variation from 5V optimum will lead to degradation of performance in relation to Bias, Scale Factor and Non-Linearity.

3

The maximum measurable input bandwidth is limited by the communication scheme in the SERIAL PERIPHERAL INTERFACE PORT section Typical Allan Variance curve showing both Angular Random Walk and Bias instability

4

Figure 2: Typical Allan Variance Curve

CRS10 Digital Rate Gyro

CRS10-01-0100-121 Rev 3

CRS10 Digital Rate Gyro

PIN DIAGRAM

Figure 3

CRS10 PIN DESCRIPTIONS

Pin Name Vdd Reset_P SPI_out SPI_in SPI_clk SPI_sel GND ANL_out

1

Pin Pin 1 No Type 1 2 3 4 5 6 7 8 I I O I I I G O

Expected Value +5 V ±0.25 V Active Low 5 V CMOS Logic 5 V CMOS Logic 5 V CMOS Logic Active Low 0V VDD/2 ±2.07 V max

Description Power Supply Connections Analogue 5 V power supply connection Connecting the Reset_P pin to GND shall reset the unit. SPI data input (MOSI). See "Serial Peripheral Interface Port" section for details. SPI data output (MISO). See "Serial Peripheral Interface Port" section for details. SPI clock signal. This signal is typically a 1 MHz clock. See "Serial Peripheral Interface Port" section for details. SPI chip select. This line is active low. See "Serial Peripheral Interface Port" section for details. Ground connection for the CRS10. Buffered analogue. This signal represents the angular rate applied to the CRS10 and is referenced to VDD/2. ANL_OUT is set to VSS if a continuous or demanded built in test (BIT) failure occurs.

Pin types include: Input (I), Output (O) and Ground (G).

CRS10 Digital Rate Gyro

CRS10-01-0100-121 Rev 3

CRS10 Digital Rate Gyro

THEORY OF OPERATION

The CRS10 uses a bulk silicon Micro-Machined ring structure, a mixed signal ASIC and a processor to make a single axis rate sensor. For legacy applications, the rate data is also converted to a analogue format (with factory programmable scale factor) and output on ANL_OUT. The digital rate data is output on the SPI interface together with other data to produce a high integrity system (see SERIAL PERIPHERAL INTERFACE PORT) Other digital data can be accessed over the SPI interface by selecting other messages (see SERIAL PERIPHERAL INTERFACE PORT)

Principle

The Silicon ring is driven in a cos2 mode shape to produce the radial velocity components required to make a Coriolis gyroscope.

1 3 2

3

SELF-TEST FUNCTION

The CRS10 includes an internal passive BIT system which monitors internal data and an externally commanded self-test feature (CBIT) that actuates the rate nulling loop in a similar manner to an applied angular rate. The primary purpose of CBIT is to synthesise the effect of real motion and stimulate the host system, particularly for analogue implementation. The CBIT mode can only be activated by selecting the CBIT bit in the SPI message for a fully digital gyro application (See SERIAL PERIPHERAL INTERFACE PORT for further details).

F

Resultant Vibration

2 1

Fc = Coriolis Force

2 1

F F

1

3

2

3

SPI CONFIGURATION ON POWER UP

Figure 5 shows the configuration status of the SPI communications upon Power up or after Reset as well as an initial User programming sequence to setup the analogue scalefactor and sensor bandwidth. The points to note are that there should be no SPI communication for the first 300ms after reset as this could result in erroneous data being transferred. The first successful SPI transfer will return message type 110 as shown (06). The analogue scalefactor and sensor bandwidth may be determined by sending User command 001 (81) and if changes are required the User command 000 (80) may be sent. It is necessary to stop all SPI communication during programming for at least 500ms as this could result in erroneous data being transferred. The first successful SPI transfer after programming will return User message type 000 as shown (80). Note that the message sequences shown in the diagram are examples only and should not be taken as a requirement. Details of the user mode codes can be found later in this document (see USER PROGRAM NOTES).

Figure 4

Figure 4 shows the movement of the silicon ring while vibrating:­ As the ring oscillates in it's natural state the ring moves in the way shown by (1). When the gyro is turned, the Coriolis force acts on the ring as shown by (2). This causes a resultant vibration 45° out of alignment with the primary vibration, as shown by (3).The force required to completely null this resultant vibration is directly proportional to the angular rate.

Implementation

Eight uniformly spaced capacitive transducers are placed around the ring to form 2 pairs of drive transducers and 2 pairs of pickoff transducers. One pair of diametrically opposed drive transducers is used to excite the cos2 mode with the phase and amplitude sensed by the corresponding pickoff transducer pair. The drive amplitude and frequency is controlled by the ASIC and Processor to establish an accurate radial velocity component at the resonant frequency of the structure. This sets the basic operating point and scalefactor of the system. A secondary rate nulling loop is set up using the other drive and pickoff transducer pairs to enable the Coriolis forces (generated by applied angular rate) to be detected and servoed to zero using digital filters within the processor. This fully closed loop operation largely removes dependency of performance on the mechanical Q of the resonator and enables a very accurate level of bias and scalefactor performance to be achieved without any compensation. The force required to null the coriolis force becomes an accurate measure of the applied angular rate. All loop controllers and filtering are implemented within the processor so the rate (and other information) is available directly in digital form. This eliminates performance variation or drift in more typical analogue control loops, as the numeric control is inherently free from ageing, temperature and manufacture tolerances. All numeric processing is synchronised to the MEMS resonant frequency, so as to eliminate phase related detector errors commonly found in MEMS sensors. The derived rate data is digitally filtered, scaled and then output via the SPI bus.

CRS10 Digital Rate Gyro

Figure 5 SPI Communications on Power up and Reset

CRS10-01-0100-121 Rev 3

CRS10 Digital Rate Gyro

SERIAL PERIPHERAL INTERFACE PORT

Communication with the CRS10 uses a serial peripheral interface (SPI) port, in which the CRS10 behaves as the slave. The SPI port includes four signals: SPI select (SPI_SEL), serial clock in (CLK_IN), MOSI or SPI data in (SPI_IN) and MISO or SPI data out (SPI_OUT). The SPI_SEL line enables the CRS10 SPI port and frames each communication see Figure 6- SPI Data Frame Structure. When the SPI_SEL line is high, SPI_OUT is held in a high impedance state and signals on CLK_IN and SPI_IN are ignored by the CRS10. A communication consists of a 48-bit data frames split into 6 8-bit bytes. The SPI port operates in full duplex mode, which means that as data is transmitted to the CRS10 on SPI_IN, it is also received from the CRS10 on SPI_OUT. Table 2 shows detailed timing information referenced from Figure 6 and Figure 7, which show's the detail of the SPI port data structure.

Table 2 - SPI Port Timing Information Parameter Value tCLK 1 tQ t1 t2 t3 t4 580 5 0.4 x tCLK 0.4 x tCLK 1 Unit µs ± 1% µs min µs min µs min µs min µs min Description CLK_IN period. Minimum quiet time required between SPI_SEL rising and start of next communication. SPI_SEL to CLK_IN setup time. CLK_IN high pulse width. CLK_IN low pulse width. Delay between successive bytes.

Control Byte:

RES bit 7 Bits bit 2-0 RES Function Message Type RES RES CBITA MT2 MT1 MT0 bit 0

Function Normal Mode: 000 = Basic rate data (default) 100 = Reserved 101 = Reserved 110 = Device configuration 1 data 111 = Device configuration 2 data User Mode: 000 = Program user data 001 = Read user data 1 = Gyro Output OK 0 = Gyro Output NOT OK 0 = ADC in range 1 = Cbit_A test in progress 0 0 = Normal mode 1 = User mode

3 4 5 6 7

Bit_OK ADC over run Cbit_A active Not used Operation Mode

Checksum:

CHK7 Byte 6 Byte 7-0 CHK6 CHK5 CHK4 CHK3 CHK2 CHK1 CHK0 bit 0

:

CHK7:CHK0 : Checksum 1s complement of the sum of bytes 1 ­ 5

The checksum is the 1s complement of sum of the previous 5 bytes

CRS10 to External System Messages

The data frames transmitted from the CRS10 to the external system are in the following format:

Byte 1 2-5 6 Function Status Byte Data Bytes Checksum

EXTERNAL SYSTEM TO CRS10 MESSAGES

The data frames from the external system to the CRS10 are in the following format:

Byte 1 2-5 6 Function Command Spare ­ Ignored(except in user mode) Checksum

Each message from the CRS10 begins with a status byte contained in byte 1 and a checksum in byte 6.

Figure 7- SPI Data Timing Diagram

CRS10 Digital Rate Gyro

~ ~~ ~~

~

CRS10-01-0100-121 Rev 3

~

CRS10 Digital Rate Gyro

Status Byte:

MODE bit 7 bit 20 PRM CBIT ADC BIT MT2 MT1 MT0 bit 0

Device Configuration Message 1 (MT2 : MT0 = 110)

Byte 1 2 3 4 5 6 Function Status Byte Bits (7:4) Bits (3:0) Bits (7:4) Bits (3:0) Bits (7:0) Bits (7:6) Bits (5:0) Checksum Description Old rate range and bandwidth data ­ overridden with User data Spare bits Model variant Software Version Assembly Plant (1:0) Yoshikawa(0:0) Year of manufacture Sum of byte 1 to 5

Message Type

Normal Mode: 000 = Basic rate data (default) 100 = Reserved 101 = Reserved 110 = Device configuration 1 data 111 = Device configuration 2 data User Mode: 000 = Program user data 001 = Read user data 0 = Gyro Output OK 1 = Gyro Output NOT OK 0 = ADC in range 1= ADC Overflow 0 = Cbit_A test not in progress 1 = Cbit_A test in progress 0 = OK 1= Fault 0 = Normal mode 1 = User mode CHK4 CHK3 CHK2 CHK1 CHK0 bit 0

3 4 5 6 7

BIT ADC over run Cbit_active PRM Operation Mode CHK6

Device Configuration Message 2 (MT2 : MT0 = 111)

Byte 1 2 3 4 5 6 Function Status Byte Bits (7:6) Bits (5:0) Bits (7:0) Bits (7:0) Bits (7:0) Checksum Description Assembly Lot Number (9:8) Week Number (5:0) Assembly Lot Number (7:0) Device serial number (15:8) Device serial number (7:0) Sum of byte 1 to 5

Checksum:

CHK7 bit 7 bit 7-0 CHK5

Note: The content of the device configuration message (byte 5) and the extended device configuration message (bytes 1 to 5) give each sensor a unique serial number. Note: If an incorrect message is received, the CRS10 will continue to transmit the message chosen in the last valid request. Upon power up, the CRS10 will output the device configuration 1 message until a valid control signal is received (0 =Ok, 1 = Fault)

:

CHK7:CHK0 : Checksum 1s complement of the sum of bytes 1 - 5

Depending on the message type requested in MT2 : MT0 of the previous message from the host, the data bytes (Data 3: Data 0) in the subsequent data frame the CRS10 contain the following data, indicated by MT2 : MT0: Definition of message header: PRM: Previous Received Message: If the previous message received is corrupt, bit 6 of the status byte is set to 1. CBIT: Commanded Built in Test, if the CBIT is demanded, bit 5 of the status byte is set to 1.. ADC: Analogue to Digital converter, if the ADC overflow is out of range, bit 4 of the status byte is set to 1. BIT: Built In Test, The built in test is a `health' check of the gyro system, if a detectable fault is detected bit 3 of the status byte is set to 1. Basic Rate Data Message (MT2 : MT0 = 000)

Byte 1 2 3 4 5 6 Function Status Byte Rate MS Rate LS DSH Temperature MS DSH Temperature MS Checksum Description Nominally ±300°/s, 0.03125°/s/lsb -50 to +145 °C, 0.125°C/lsb Sum of byte 1 to 5

EXTERNAL INTERFACE DISCRETE SIGNALS

A discrete signal is part of the external host interface of the CRS10:

RESET_IN (input)

The CRS10 has a discrete input which is capable of resetting the device. The RESET_IN input is an active-low signal. When pulled low for a minimum of 2µs, CRS10 enters a reset state. The timing of the reset sequence is shown in Figure 8.

Figure 8 - RESET_IN Timing

RESET_IN Logic Levels RESET_IN = 0 RESET_IN = 1 After a minimum of 2µs, the CRS10 is held in reset. The CRS10 is in normal operation.

CRS10 Digital Rate Gyro

CRS10-01-0100-121 Rev 3

CRS10 Digital Rate Gyro

Analogue Rate Output Channel

The analogue rate output from the CRS10, is referenced to VDD/2, bipolar (around VDD/2) and directly proportional to the applied rate. The analogue rate has a minimum voltage range of ±2.0 V with respect to VDD/2. When positive rate is applied, the voltage increases (within the rate limits of the gyro). When a BIT failure occurs (with the exception of CBIT being asserted), the analogue rate output falls to within 0.1V of VSS (Ground 0V) .

CRS10 Digital Rate Gyro

CRS10-01-0100-121 Rev 3

CRS10 Digital Rate Gyro

USER PROGRAM NOTES

To write the USER options for Bandwidth and Analogue scale factor the following inputs are required to be sent to the sensor from the host

Bytes 1 80 2 AA 3 06 4 5E 5 FC 6 75

Definition:

Byte 1 2 3..4 5 6 Function Status byte Programmed Bandwidth selection code Programmed Analogue scale factor code Not used (00) Checksum

In this example Byte 2 (06) - 75Hz bandwidth and Byte 3 (5E) and Byte 4 (FC) give a 24mV/°/s scale factor. To read the Bandwidth and Analogue scale factor that has been programmed into the CRS10 (default configuration) or to cross check user input The following command should be sent from the Host.

Bytes

Definition:

Byte 1 2 3 4..5 6 Function Command byte= 80 User Mode activation code= AA Bandwidth selection code Analogue scale factor code Checksum

Bandwidth selection codes available for Byte 3 are

Bandwidth Hz 5 Hz 10 Hz 25 Hz 40 Hz 50 Hz 60 Hz 75 Hz 100 Hz 00 01 02 03 04 05 06 Default 07 Code hex

1 81

2 AA

3 00

4 00

5 00

6 D4

Definition:

Byte 1 2 3..5 6 Function Command byte= 81 User Mode activation code= AA Not used (00) Checksum

The response from the CRS10 will be ( example only)

Bytes 1 2 06 3 5E 4 FC 5 00 6 1E

The determine the scale factor selection code, the following equation is required to be used, Analogue Scale factor = Integer (Required Analogue scale factor (mV/°/s) * 1013.159)

Scale Factor mV/°/s 5 10 15 20 24 30 50 60 Rate Range °/s 360 180 120 90 75 60 36 30 Code hex 13C9 2793 3B5D 4F27 5EFB 76BA C5E1 ED75

81

Definition:

Byte 1 2 3..4 5 6 Function Status byte Programmed Bandwidth selection code Programmed Analogue scale factor code Not used (00) Checksum

Note, this is a 16 bit unsigned number, where maximum input can be FFFF or 64 mV/°/s. The response from the CRS10 will be (example only)

Bytes 1 80 2 06 3 5E 4 FC 5 00 6 1F

CRS10 Digital Rate Gyro

CRS10-01-0100-121 Rev 3

CRS10 Digital Rate Gyro

MECHANICAL DESIGN

Package Outline Dimensions

Figure 9 - Package Outline Dimensions

Recommended Solder Conditions Vertical or Horizontal Bracket

for

the

The CRS10 Vertical and Horizontal bracket arrangements have been designed to be reflow soldered to a PCB. It is recommended that lead-free solder flow conditions should not exceed 235°C with a dwell over 220°C of less than 60 seconds. However, short duration dwells of 10 seconds or less at temperatures of up to 260°C can be tolerated. On completion on the soldering process the CRS10 can be easily fitted in to the bracket.

CRS10 Digital Rate Gyro

CRS10-01-0100-121 Rev 3

CRS10 Digital Rate Gyro

CRS10 MEAN TIME BEFORE FAILURE (MTBF) CALCULATIONS

7

CRS10 FPMH vs Temperature

Failures Per Million Hours

The MTBF of any component or system is dependant upon the operational temperature and vibration environment. Therefore, specifying a numeric to every question on this issue is difficult as different customers wish to use the information for different purposes. The CRS10 figures have been calculated using MIL-HBK217F for a parts stress analysis. The table and graph show the Failures Per Million Hours (FPMH) calculated in a Ground Mobile vibration environment, which can be used to calculate any specific MTBF.

6

5

4

3

2

1

0 -40

-30

-20

-10

0

10

20

30

40

50

60

70

80

90

100

110

120

130

Temperature (°C)

TEMP -40 °C -35 °C -30 °C -25 °C -20 °C -15 °C -10 °C -5 °C 0 °C 5 °C 10 °C 15 °C 20 °C 23 °C 25 °C 30 °C 35 °C 40 °C 45 °C 50 °C 55 °C 60 °C 65 °C 70 °C 75 °C 80 °C 85 °C 90 °C 95 °C 100 °C 105 °C 110 °C 115 °C 120 °C 125 °C

FPMH 0.603 0.604 0.606 0.609 0.612 0.616 0.621 0.628 0.637 0.648 0.662 0.681 0.704 0.721 0.734 0.772 0.820 0.881 0.956 1.048 1.161 1.297 1.459 1.651 1.877 2.139 2.441 2.789 3.185 3.635 4.144 4.716 5.358 6.074 6.871 Looking up the failure rate from the table, the FPMH = 0.881 Substituting into the equation: Examples: 1. MTBF of CRS10 operated at +40°C The MTBF is next calculated in the same way as for a single specific temperature. Calculation Method To calculate the MTBF at any specific temperature, simply use the following equation, and the appropriate data from the table:

MTBF =

1× 10 6 FPMH

Calculation for a specific usage profile is a little more involved. First it is necessary to determine the percentage time the CRS10 would be operating at any particular temperature, and for each of those temperatures, determine a factored FPMH using the following equation:

fpmhT = usage% × FPMH 2

The resultant FPMH figure for the applied usage profile is then calculated using the following equation:

FPMH =

fpmh

2

T

1×10 6 1×10 6 MTBF = = = 1,135,073 Hrs FPMH 0.881

Thus the MTBF = 1,135,073 Hrs

CRS10 Digital Rate Gyro

CRS10-01-0100-121 Rev 3

CRS10 Digital Rate Gyro

2. MTBF of CRS10 with the following usage profile: 6% @ -40°C; 65% @ 23°C; 20% @ 60°C; 8% @ 80°C; 1% @ 85°C

Firstly, look up the FPMH figure for each of the temperatures in the profile from the data table. Next, compute the factored fpmh numbers. The results of this operation are shown in the following table:

TEMP -40°C +23°C +60°C +80°C +85°C

FPMH 0.603 0.721 1.297 2.139 2.441

usage% 6% 65% 20% 8% 1%

fpmhT 0.148 0.581 0.580 0.605 0.244

The combined FPMH figure can now be calculated as follows:

FPMH =

fpmh

2

T

= 1.121 = 1.059

Finally, the MTBF for the usage profile is calculated:

1 × 10 6 1 × 10 6 MTBF = = = 944,287 Hrs FPMH 1.059

Thus the MTBF = 944,287 Hrs

CRS10 Digital Rate Gyro

CRS10-01-0100-121 Rev 3

Silicon Sensing Systems reserves the right to make changes without further notice to any products herein. Silicon Sensing Systems makes no warranty, representation or guarantee regarding the suitability of its products for any particular purpose, nor does Silicon Sensing Systems assume any liability arising out of the application or use of any product or circuit, and specifically disclaims any and all liability, including without limitation consequential or incidental damages. "Typical" parameters which may be provided in Silicon Sensing Systems datasheets and/or specifications can and do vary in different applications and actual performance may vary over time. All operating parameters, including "Typicals" must be validated for each customer application by customer's technical experts. Silicon Sensing Systems does not convey any licence under its patent rights nor the rights of others. Silicon Sensing Systems products are not intended for any application in which the failure of the Silicon Sensing Systems product could create a situation where personal injury or death may occur. Should Buyer purchase or use Silicon Sensing Systems products for any such unintended or unauthorised application, Buyer shall indemnify and hold Silicon Sensing Systems and its officers, employees, subsidiaries, affiliates, and distributors harmless against all claims, costs, damages, and expenses, and reasonable legal fees arising out of, directly or indirectly, any claim of personal injury or death associated with such unintended or unauthorised use, even if such claim alleges that Silicon Sensing Systems was negligent regarding the design or manufacture of the part.

Phone: +44 1752 723330 · Fax: +44 1752 723331 [email protected] · www.siliconsensing.com

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