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Technical content

Features

  • Measuring ranges ±30° SCA61T-FAHH1G and ± 90° SCA61T-FA1H1G
  • 0.0025° resolution (10 Hz BW, analog output)
  • Sensing element controlled over damped frequency response (-3dB 18Hz)
  • Robust design, high shock durability (20000g)
  • Excellent stability over temperature and time
  • Single +5 V supply
  • Ratiometric analog voltage outputs
  • Digital SPI inclination and temperature output
  • Comprehensive failure detection features o True self test by deflecting the sensing elements’ proof mass by electrostatic force. o Continuous sensing element interconnection failure check. o Continuous memory parity check.
  • RoHS compliant
  • Compatible with Pb-free reflow solder process

Applications

  • Platform leveling and stabilization
  • Leveling instruments
  • Acceleration and motion measurement Figure 1. Functional block diagram Data Sheet

Murata Electronics Oy Subject to changes 2/17 TABLE OF CONTENTS

Murata Electronics Oy Subject to changes 3/17

1 Electrical Specifications

The SCA61T product family comprises two versions, the SCA61T -FAHH1G and the SCA61T - FA1H1G, that differ in measurement range. The product version specif ic performance specifications are listed in the following table below. All other specifications are common to both versions. Vdd=5.00V and ambient temperature unless otherwise specified.

1.1 Absolute Maximum Ratings

Supply voltage (VDD) Voltage at input / output pins Storage temperature Operating temperature Mechanical shock -0.3 V to +5.5V -0.3V to (VDD + 0.3V) -55°C to +125°C -40°C to +125°C Drop from 1 meter on a concrete surface (20000g). Powered or non-powered

1.2 Performance Characteristics

Parameter Condition SCA61T- FAHH1G SCA61T- FA1H1G Units Measuring range Nominal ±30 ±0.5 ±90 ±1.0 g Frequency response –3dB LP (1 8-28 8-28 Hz Offset (Output at 0g) Ratiometric output Vdd/2 Vdd/2 V Offset calibration error ±0.11 ±0.23 ° Offset Digital Output 1024 1024 LSB Sensitivity between 0…1° (2 V/g mV/° Sensitivity calibration error ±0.5 ±0.5 % Sensitivity Digital Output 1638 819 LSB / g Offset temperature dependency Sensitivity temperature dependency Typical non-linearity Measuring range ±0.11 ±0.57 ° Digital output resolution between 0…1° (2 0.035 0.07 Bits ° / LSB Analog output resolution Bandwidth 10 Hz (3 0.0025 0.0025 ° Cross-axis sensitivity Max. 4 4 % Note 1. The frequency response is determined by the sensing element’s internal gas damping. Note 2. The angle output has SIN curve relationship to voltage output refer to paragraph 2.2 Note 3. Resolution = Noise density * √(bandwidth)

Murata Electronics Oy Subject to changes 4/17

1.3 Electrical Characteristics

Parameter Condition Min. Typ Max. Units Supply voltage Vdd 4.75 5.0 5.25 V Current consumption Vdd = 5 V; No load 2.5 4 mA Operating temperature -40 +125 °C Analog resistive output load Vout to Vdd or GND 10 kOhm Analog capacitive output load Vout to Vdd or GND 20 nF Start-up delay Reset and parity check 10 ms

1.4 SPI Interface DC Characteristics

Parameter Conditions Symbol Min Typ Max Unit

1.4.1.1.1 Input terminal CSB

Pull up current VIN = 0 V IPU 13 22 35 µA Input high voltage VIH 4 Vdd+0.3 V Input low voltage VIL -0.3 1 V Hysteresis VHYST 0.23*Vdd V Input capacitance CIN 2 pF

1.4.1.1.2 Input terminal MOSI, SCK

Pull down current VIN = 5 V IPD 9 17 29 µA Input high voltage VIH 4 Vdd+0.3 V Input low voltage VIL -0.3 1 V Hysteresis VHYST 0.23*Vdd V Input capacitance CIN 2 pF

1.4.1.1.3 Output terminal MISO

Output high voltage I > -1mA VOH Vdd- 0.5 V Output low voltage I < 1 mA VOL 0.5 V Tristate leakage 0 < VMISO < Vdd ILEAK 5 100 pA

1.5 SPI Interface AC Characteristics

Parameter Condition Min. Typ. Max. Units Output load @500kHz 1 nF SPI clock frequency 500 kHz Internal A/D conversion time 150 µs Data transfer time @500kHz 38 µs

1.6 SPI Interface Timing Specifications

Figure 2. Timing diagram for SPI communication

1.7 Electrical Connection

floating. Self-test can be activated applying logic “1” (positive supply voltage level) to ST pin (pin 6). Figure 3. SCA61T electrical connection

1 SCK Input Serial clock

2 MISO Output Master in slave out; data output

3 MOSI Input Master out slave in; data input

4 GND Supply Ground

5 CSB Input Chip select (active low)

6 ST Input Self test input

7 Out Output Output

8 VDD Supply Positive supply voltage (+5V DC)

1.8 Typical Performance Characteristics

following diagrams. The 3 sigma limits represents 99.73% of the SCA61T population. Figure 4. Typical temperature dependency of the SCA61T offset

1 SCK

2 MISO

3 MOSI

4 GND

8 VDD

7 OUT

5 CSB

Figure 5. Typical temperature dependency of SCA61T sensitivity

1.9 Additional External Compensation

2 Functional Description

2.1 Measuring Directions

Figure 8. The measuring direction of the SCA61T

2.2 Voltage to Angle Conversion

with SCA61T-FAHH1G and 2 V/g with SCA61T-FA1H1G. the angle measurement error if straight line conversion is used.

2.3 Ratiometric Output

used, the error caused by reference voltage variation is automatically compensated for.

2.4 SPI Serial Interface

products always operates as a slave device in master-slave operation mode. of wires for serial data input (MOSI), serial data output (MISO) and serial clock (SCK). Figure 9. Typical SPI connection

Murata Electronics Oy Subject to changes 11/17 MISO master in slave out SCA61T → µP SCK serial clock µP → SCA61T CSB chip select (low active) µP → SCA61T Each transmission starts with a falling edge of CSB and ends with the rising edge. During transmission, commands and data are controlled by SCK and CSB according to the following rules:

  • commands and data are shifted; MSB first, LSB last
  • each output data/status bits are shifted out on the falling edge of SCK (MISO line)
  • each bit is sampled on the rising edge of SCK (MOSI line)
  • after the device is selected with the falling edge of CSB, an 8-bit command is received. The command defines the operations to be performed
  • the rising edge of CSB ends all data transfer and resets internal counter and command register
  • if an invalid command is received, no data is shifted into the chip and the MISO remains in high impedance state until the falling edge of CSB. This reinitializes the serial communication.
  • data transfer to MOSI continues immediately after receiving the command in all cases where data is to be written to SCA61T’s internal registers
  • data transfer out from MISO starts with the falling edge of SCK immediately after the last bit of the SPI command is sampled in on the rising edge of SCK
  • maximum SPI clock frequency is 500kHz
  • maximum data transfer speed for RDAX is 5300 samples per sec / channel The SPI command can be either an individual command or a combination of command and data. In the case of combined command and data, the input data follows uninterruptedly the SPI command and the output data is shifted out parallel with the input data The SPI interface uses an 8- bit instruction (or command) register. The list of commands is given in Table below. Command name Command format Description: MEAS 00000000 Measure mode (normal operation mode after power on) RWTR 00001000 Read temperature data register STX 00001110 Activate Self test for X-channel STY 00001111 Activate Self test for Y-channel RDAX 00010000 Read X-channel acceleration RDAY 00010001 Read Y-channel acceleration Measure mode (MEAS) is standard operation mode after power -up. During normal operation, the MEAS command is the exit command from Self test. Read temperature data register (RWTR) reads temperature data register during normal operation without effecting the operation. Temperature data register is updated every 150 µs. The load operation is disabled whenever the CSB signal is low, hence CSB must stay high at least 150 µs prior the RWTR command in order to guarantee correct data. The data transfer is presented in Figure below. The data is transferred MSB first. In normal operation, it does not matter what data is written into temperature data register during the RWTR command and hence writing all zeros is recommended.

Figure 10. Command and 8 bit temperature data transmission over the SPI stored in acceleration data register X. Figure 11. Command and 11 bit acceleration data transmission over the SPI

2.5 Digital Output to Angle Conversion

Murata Electronics Oy Subject to changes 13/17 [ ] [ ] [ ]   −= LSB/g LSBLSBarcsin Sens DD outout α where; Dout digital output (RDAX) Dout@0° digital offset value, nominal value = 1024 α angle Sens sensitivity of the device. (SCA61T-FAHH1G: 1638, SCA61T-FA1H1G: 819) As an example following table contains data register values and calculated differential digital output values with -5, -1 0, 1 and 5 degree tilt angles. Angle [°] Acceleration [mg] RDAX (SCA61T- FAHH1G) RDAX (SCA61T- FA1H1G) -5 -87.16 dec: 881 bin: 011 0111 0001 dec: 953 bin: 011 1011 1001 -1 -17.45 dec: 995 bin: 011 1110 0011 dec: 1010 bin: 011 1111 0010 0 0 dec: 1024 bin: 100 0000 0000 dec: 1024 bin: 100 0000 0000 1 17.45 dec: 1053 bin: 100 0001 1101 dec: 1038 bin: 100 0000 1110 5 87.16 dec: 1167 bin: 100 1000 1111 dec: 1095 bin: 100 0100 0111

2.6 Self Test and Failure Detection Modes

To ensure reliable measurement results the SCA61T has continuous interconnection failure and calibration memory validity detection. A detected failure forces the output signal close to power supply ground or VDD level, outside the normal output range. The normal output ranges are: The calibration memory validity is verified by continuously running parity check for the control register memory content. In the case where a parity error is detected the control register is automatically re-loaded from the EEPROM. If a new parity error is detected after re-loading data both analog output voltage is forced to go close to ground level (<0.25 V) and SPI outputs goes below 102 counts. The SCA61T also includes a separate self test mode. The true self test simulates acceleration, or deceleration, using an electrostatic force. The electrostatic force simulates acceleration that is high enough to deflect the proof mass to the extreme positive position, and this causes the output signal to go to the maximum value. The self test function is activated either by a separate on- off command on the self test input, or through the SPI. The self-test generates an electrostatic force, deflecting the sensing element’s proof mass, thus checking the complete signal path. The true self test performs following checks:

  • Sensing element movement check
  • ASIC signal path check
  • PCB signal path check
  • Micro controller A/D and signal path check The created deflection can be seen in both the SPI and analogue output. The self test function is activated digitally by a STX command, and de-activated by a MEAS command. Self test can be

self test Input high voltage level is 4 – Vdd+0.3 V and input low voltage level is 0.3 – 1 V. Figure 12. Self test wave forms V1 = initial output voltage before the self test function is activated. V2 = output voltage during the self test function. initial value after the specified stabilization time. After a longer time (max. 1 second) V1=V3. T5 = Rise time during self test.

2.7 Temperature Measurement

The SCA61T has an internal temperature sensor, which is used for internal offset compensation. the temperature measurement is about ±1 °C.

3 Application Information

3.1 Recommended Circuit Diagrams and Printed Circuit Board Layouts

both the SCA61T and Analog/Digital converter. Use low pass RC filter with 5.11 kΩ and 10nF on the SCA61T output to minimize clock noise. power supply or GND connection strips on PCB. Figure 13. Analog connection and layout example Figure 14. SPI connection example

3.2 Recommended Printed Circuit Board Footprint

Figure 15. Recommended PCB footprint

4 Mechanical Specifications and Reflow Soldering

4.1 Mechanical Specifications (Reference only)

RoHS compliance: RoHS compliant lead free component. Co-planarity error 0.1mm max. Figure 16. Mechanical dimensions of the SCA61T. (Dimensions in mm)

4.2 Reflow Soldering

normal SMD pick-and-place equipment. Figure 17. Recommended SCA61T body temperature profile during reflow soldering. Ref. Average ramp-up rate (TL to TP) 3°C/second max. 3°C/second max.

  • Preheating time and temperatures according to solder paste manufacturer.
  • It is important that the part is parallel to the PCB plane and that there is no angular alignment error from intended measuring direction during assembly process.
  • Wave soldering is not recommended.
  • Ultrasonic cleaning is not allowed. The sensing element may be damaged by ultrasonic cleaning process.