ADXRS150

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Technical content

±150°/s Single Chip Yaw Rate Gyro with Signal Conditioning ADXRS150

FEATURES

Complete rate gyroscope on a single chip Z-axis (yaw rate) response High vibration rejection over wide frequency 0.05°/s/√Hz noise 2000 g powered shock operation Self-test on digital command Temperature sensor output Precision voltage reference output Absolute rate output for precision applications

5 V single-supply operation

Ultrasmall and light (< 0.15 cc, < 0.5 gram)

APPLICATIONS

Inertial measurement units Guidance and control Platform stabilization GENERAL DESCRIPTION The ADXRS150 is a complete angular rate sensor (gyroscope) that uses Analog Devices’ surface-micromachining process to make a functionally complete and low cost angular rate sensor integrated with all of the required electronics on one chip. The manufacturing technique for this device is the same high volume BIMOS process used for high reliability automotive airbag accelerometers. The output signal, RATEOUT (1B, 2A), is a voltage proportional to the angular rate about the axis normal to the top surface of the package (see Figure 2). A single external resistor can be used to lower the scale factor. An external capacitor is used to set the bandwidth. Other external capacitors are required for operation (see Figure 21). A precision reference and a temperature output are also pro- vided for compensation techniques. Two digital self-test inputs electromechanically excite the sensor to test the operation of both sensors and the signal conditioning circuits. The ADXRS150 is available in a 7 mm × 7 mm × 3 mm BGA surface-mount package. FUNCTIONAL BLOCK DIAGRAM 2G 1F 7F 6A 7D7C7B 4A 5A 7E 6G PDD 12V ADXRS150 47nF 22nF100nF 22nF CP2 CP1 PGND CP4 CP3 CP5 CHARGE PUMP/REG. TEMP PTAT RATEOUT 2.5V π DEMODRATE SENSOR SELF TEST 100nF 100nF CMIDAGNDAVCC ST1 ST2 CORIOLIS SIGNAL CHANNEL RSEN1 RSEN2 COUT SUMJ ROUT 2.5V REF 180kΩ 1% RESONATOR LOOP Figure 1. Rev. A Information fur nished by An alog Devices is believed t o be accurate an d r eliable. However, no r esponsibility is assumed by Anal og De vices fo r its use, nor for a ny infringements of patents or other rights of third parties that m ay result from its use. Specifications subject to change without notice. No license is granted by implication or otherwise under any patent or p atent rights of A nalog Devices. Trademarks and registered trademarks are the property of their respective companies. Tel: 781.329.4700 www.analog.com Fax: 781.326.8703 © 2003 Analog Devices, Inc. All rights reserved.

REVISION HISTORY

1/03—Data Sheet Changed from REV. 0 to REV. A Rev. A | Page 2 of 12

Table 1. @TA = 25°C, VS = 5 V, Bandwidth = 80 Hz (COUT = 0.01 µF), Angular Rate = 0°/s, Unless Otherwise Noted.

2.5 V REFERENCE

1 All min and max specifications are guaranteed. Typical specifications are not tested or guaranteed. 3 Specification refers to the maximum extent of this parameter as a worst-case value at TMIN or TMAX. 5 Self-test response varies with temperature. Refer to the Self-Test Function section for details.

Table 2. ADXRS150 Absolute Maximum Ratings or other means to achieve this requirement. 2000 g and exceed the absolute maximum rating of the device. Care should be exercised in handling to avoid damage. clockwise when looking down at the package lid. Figure 2. RATEOUT Signal Increases with Clockwise Rotation

Rev. A | Page 9 of 12 of RSEN1 and RSEN2) at about 4.5 kΩ nominal, and CMID is less well controlled since RSEN1 and RSEN2 have been used to trim the rate sensitivity during manufacturing and have a ±35% toler- ance. Its primary purpose is to limit the high frequency demodulation artifacts from saturating the final amplifier stage. Thus, this pole of nominally 400 Hz @ 0.1 µF need not be precise. Lower frequency is preferable, but its variability usually requires it to be about 10 times greater (in order to preserve phase integrity) than the well-controlled output pole. In general, both –3 dB filter frequencies should be set as low as possible to reduce the amplitude of these high frequency artifacts as well as to reduce the overall system noise. Increasing Measurement Range The full-scale measurement range of the ADXRS150 can be increased by placing an external resistor between the RATEOUT (1B, 2A) and SUMJ (1C, 2C) pins, which would parallel the internal ROUT resistor that is factory-trimmed to 180 kΩ. For example, a 330 kΩ external resistor will give approximately 8.1 mV/°/sec sensitivity and a commensurate ~50% increase in the full-scale range. This is effective for up to a 4× increase in the full-scale range (minimum value of the paral- lel resistor allowed is 45 kΩ). Beyond this amount of external sensitivity reduction, the internal circuitry headroom require- ments prevent further increase in the linear full-scale output range. The drawbacks of modifying the full-scale range are the additional output null drift (as much as 2°/sec over tempera- ture) and the readjustment of the initial null bias (see the Null Adjust section). Temperature Output and Calibration It is common practice to temperature-calibrate gyros to improve their overall accuracy. The ADXRS150 has a tempera- ture-proportional voltage output that provides input to such a calibration method. The voltage at TEMP (3F, 3G) is nominally

2.5 V at 27°C and has a PTAT (proportional to absolute tem-

perature) characteristic of 8.4 mV/°C. Note that the TEMP output circuitry is limited to 50 µA source current. Using a 3-point calibration technique, it is possible to calibrate the ADXRS150’s null and sensitivity drift to an overall accuracy of nearly 300°/hour. An overall accuracy of 70°/hour or better is possible using more points. Limiting the bandwidth of the device reduces the flat-band noise during the calibration process, improving the measurement accuracy at each calibration point. Using the ADXRS150 with a Supply- Ratiometric ADC The ADXRS150’s RATEOUT signal is nonratiometric, i.e., nei- ther the null voltage nor the rate sensitivity is proportional to the supply. Instead they are nominally constant for dc supply changes within the 4.75 V to 5.25 V operating range. If the ADXRS150 is used with a supply-ratiometric ADC, the ADXRS150’s 2.5 V output can be converted and used to make corrections in software for the supply variations. Null Adjustment Null adjustment is possible by injecting a suitable current to SUMJ (1C, 2C). Adding a suitable resistor to either ground or the positive supply is a simple way of achieving this. The nomi- nal 2.5 V null is for a symmetrical swing range at RATEOUT (1B, 2A). However, a nonsymmetric output swing may be suit- able in some applications. Note that if a resistor is connected to the positive supply, supply disturbances may reflect some null instability. Digital supply noise should be avoided particularly in this case (see Supply and Common Considerations section). The resistor value to use is approximately: )V – )/(V( R NULL1NULL0NULL 00018052 , . ×= VNULL0 is the unadjusted zero rate output, and VNULL1 is the target null value. If the initial value is below the desired value, the resistor should terminate on common or ground. If it is above the desired value, the resistor should terminate on the 5 V sup- ply. Values typically are in the 1 MΩ to 5 MΩ range. If an external resistor is used across RATEOUT and SUMJ, then the parallel equivalent value is substituted into the above equa- tion. Note that the resistor value is an estimate since it assumes VCC = 5.0 V and VSUMJ = 2.5 V. Self-Test Function The ADXRS150 includes a self-test feature that actuates each of the sensing structures and associated electronics in the same manner as if subjected to angular rate. It is activated by standard logic high levels applied to inputs ST1 (5F, 5G), ST2 (4F, 4G), or both. ST1 will cause the voltage at RATEOUT to change about –0.66 V and ST2 will cause an opposite change of +0.66 V. The self-test response follows the viscosity temperature dependence of the package atmosphere, approximately 0.25%/°C. Activating both ST1 and ST2 simultaneously is not damaging. Since ST1 and ST2 are not necessarily closely matched, actuat- ing both simultaneously may result in an apparent null bias shift. Continuous Self-Test The one-chip integration of the ADXRS150 gives it higher reli- ability than is obtainable with any other high volume manufac- turing method. Also, it is manufactured under a mature BIMOS process that has field-proven reliability. As an additional failure detection measure, power-on self-test can be performed. How- ever, some applications may warrant continuous self-test while

Figure 27. BGA-32 (Bottom View) Table 3. Pin Function Descriptions—32-Lead BGA

3.65 MAX

7.00 BSC SQ

4.80 BSC

Figure 28. 32-Lead Chip Scale Ball Grid Array [CSPBGA] degradation or loss of functionality. Table 4. Ordering Guide tered t rademarks ar e t he p roperty of their respective companies .