LIS302ALB STMICROELECTRONICS | Alldatasheet
Document overview
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- PDF pages: 17
Technical content
Datasheet sections
- 1 Block diagram
- 1.1 Pin description
- 2 Mechanical and electrical specifications
- 2.1 Mechanical characteristics
- 2.2 Electrical characteristics
- 2.3 Absolute maximum ratings
- 2.4 Terminology
- 3 Functionality
- 3.1 Sensing element
- 3.2 IC interface
- 3.3 Factory calibration
- 4 Application hints
- 4.1 Soldering information
- 5 Typical performance characteristi cs
- 5.1 Mechanical characteristics at 25°C
- 5.2 Mechanical characteristics derived from measurement in the
- 5.3 Electrical characteristics at 25°C
- 6 Package information
- 7 Revision history
Features
■ 3.0V to 3.6V supply voltage ■ ~2mW power consumption ■ ±2g full-scale ■ 3 acceleration channels plus multiplexed analog output ■ Ratiometric output voltage ■ Power down mode ■ Embedded self test ■ 10000g high shock survivability ■ ECOPACK® RoHS and “Green” compliant (see Section 6)
Description
The LIS302ALB is a miniaturized low-power three-axis linear accelerometer. It includes a sensing element and an IC interface to provide an analog signal to the external world. The sensing element, capable of detecting the acceleration, is manufactured using a dedicated process developed by ST to produce motion sensors and actuators in silicon. The IC interface is manufactured using a CMOS process that allows to design a dedicated circuit which is trimmed to better match the sensing element characteristics. The device can be operated from 2.16V to 3.6V. The LIS302ALB has a full scale of ±2g and it is capable of measuring accelerations over a maximum bandwidth of 2.0kHz. The device bandwidth may be reduced by using external capacitances. A self-test capability allows the user to check the functioning of the sensor in the final application. The device has three analog acceleration output plus an embedded multiplexer that allows to redirect the analog outputs onto a single pin for operation with a single channel A/D converter. The LIS302ALB is available in plastic Thin Land Grid Array package (TLGA) and it is guaranteed to operate over an extended temperature range from -40°C to +85°C. The LIS302ALB belongs to a family of products suitable for a variety of applications: – Mobile terminals – Gaming and Virtual Reality input devices – Free-fall detection for data protection – Antitheft systems and Inertial Navigation – Appliance and Robotics. Order codes Note: Tape & reel parts are compliant to International Standard EIA-481. LGA-14 (3x5x0.9mm) Part number Temperature range, °CP a c k a g e P a c k i n g LIS302ALB -40°C to +85°C LGA-14 Tray LIS302ALBTR -40°C to +85°C LGA-14 Tape & reel
1 Block diagram
Figure 1. Block diagram
1.1 Pin description
Figure 2. Pin connection
Table 1. Pin description
1 Reserved Connect to Vdd
2 Reserved Connect to Vdd
3 S0 Mux selector 0 (Connect to Vdd or to GND)
4 S1 Mux selector 1 (Connect to Vdd or to GND)
5 ST Self Test (Logic 0: normal mode; Logic 1: Self-test)
6 PD Power Down (Logic 0: normal mode; Logic 1: Power-Down mode)
7 Voutx Output Voltage X channel
8 Vouty Output Voltage Y channel
9 Voutz Output Voltage Z channel
10 GND 0V supply
11 Vout Multiplexer output
12 Aux_In Auxiliary input
13 Vdd Power supply
14 Reserved Connect to Vdd
2 Mechanical and electrical specifications
2.1 Mechanical characteristics. Table 2. Mechanical characteristics (1)
- The product is factory calibrated at 3.3V . The operational power supply range is specified in table 3. Since the device is
ratiometric Voff, So and Vt parameters will vary with supply voltage.
- Typical specificat ions are not guaranteed
- Guaranteed by wafer level test and measurement of initial offset and sensitivity
- Zero-g level and sensitivity are ratiometric to supply voltage
- Contribution to the measuring output of an inclination/acceleration along any perpendicular axis
- Self test output voltage change” is defined as Vout
- Self test output voltage change” varies cubically with supply voltage
- Minimum resonance frequency Fres=2 .0kHz. Sensor bandwidth=1/(2*π*32kΩ*Cload)
2.2 Electrical characteristics
Table 3. Electrical characteristics (1)
- Typical specificat ions are not guaranteed
- Minimum resonance frequency Fres=2 .0kHz. Device bandwidth=1/(2*π*32kΩ*Cload)
2.3 Absolute maximum ratings
2.4 Terminology
little over temperature (see sensitivity change vs. temperature) and also very little over time. Table 4. Absolute maximum ratings
Mechanical and electrical specifications LIS302ALB over lifetime. The Zero-g level tolerance describes the range of Zero-g levels of a population of sensors. Self Test allows to check the sensor functionality without moving it. The Self Test function is off when the ST pin is connected to GND. When the ST pin is tied at Vdd an actuation force is applied to the sensor, simulating a definite input acceleration. In this case the sensor outputs will exhibit a voltage change in their DC levels which is related to the selected full scale and depending on the Supply Voltage through the device sensitivity. When ST is activated, the device output level is given by the algebraic sum of the signals produced by the acceleration acting on the sensor and by the electrostatic test-force. If the output signals change within the amplitude specified inside Table 2, than the sensor is working properly and the parameters of the interface chip are within the defined specification. Output impedance describes the resistor inside the output stage of each channel. This resistor is part of a filter consisting of an external capacitor of at least 2.5nF and the internal resistor. Due to the resistor level, only small inexpensive external capacitors are needed to generate low corner frequencies. When interfacing with an ADC it is important to use high input impedance input circuitries to avoid measurement errors. Note that the minimum load capacitance forms a corner frequency close to the resonance frequency of the sensor. In general the smallest possible bandwidth for a particular application should be chosen to get the best results.
3 Functionality
The LIS302ALB is an “piccolo” low-power, analog output three-axis linear accelerometer packaged in a LGA package. The complete device includes a sensing element and an IC interface able to take the information from the sensing element and to provide an analog signal to the external world. The sensor provides the three accelerations and one multiplexed analog output.
3.1 Sensing element
A proprietary process is used to create a surface micro-machined accelerometer. The technology allows to carry out suspended silicon structures which are attached to the substrate in a few points called anchors and are free to move in the direction of the sensed acceleration. To be compatible with the traditional packaging techniques a cap is placed on top of the sensing element to avoid blocking the moving parts during the moulding phase of the plastic encapsulation. When an acceleration is applied to the sensor the proof mass displaces from its nominal position, causing an imbalance in the capacitive half-bridge. This imbalance is measured using charge integration in response to a voltage pulse applied to the sense capacitor. At steady state the nominal value of the capacitors are few pF and when an acceleration is applied the maximum variation of the capacitive load is in fF range.
3.2 IC interface
The complete signal processing uses a fully differential structure, while the final stage converts the differential signal into a single-ended one to be compatible with the external world. The first stage is a low-noise capacitive amplifier that implements a Correlated Double Sampling (CDS) at its output to cancel the offset and the 1/f noise. The produced signal is then sent to three different S&Hs, one for each channel, and made available to the outside. The device provides an embedded multiplexer to allow the redirection of either the analog output signals Voutx, Vouty, and Voutz or of an auxiliary input signal onto a single pin for operation with a single channel A/D converter. All the analog parameters (output offset voltage and sensitivity) are ratiometric to the voltage supply. Increasing or decreasing the voltage supply, the sensitivity and the offset will increase or decrease linearly. The feature provides the cancellation of the error related to the voltage supply along an analog to digital conversion chain. The product is factory calibrated at 3.3V. For availability of different supply voltage in the maximum range [2.16V, 3.6V] contact factory
3.3 Factory calibration
The IC interface is factory calibrated for sensitivity (So) and Zero-g level (Voff). The trimming values are stored inside the device in a non volatile structure. Any time the device is turned on, the trimming parameters are downloaded into the registers to be employed during the normal operation. This allows the user to employ the device without further calibration.
4 Application hints
Figure 3. LIS302ALB electrical Connection be placed as near as possible to the device (common design practice). Cload(x, y, z) is required in any case. An external capacitor can be added to the Vout pin. Values below 10 pF are recommended.
4.1 Soldering information
qualified for soldering heat resistance according to JEDEC J-STD-020C. soldering. Land pattern and soldering recommendations are available at www.st.com/mems. Figure 4. Output Response vs. Orientation Figure 4 refers to LIS302ALB powered at 3.3V. Table 5. Filter capacitor selection, C load (x,y,z)
1 Hz 5 μF
20 Hz 250nF
50 Hz 100nF
100 Hz 50nF
200 Hz 25nF
500 Hz 10nF
Table 6. MUX I/O table
5 Typical performance characteristics
5.1 Mechanical characteristics at 25°C
Figure 5. X-axis Zero-g level and Sensitivity at 3.3V Figure 6. Y-axis Zero-g level and Sensitivity at 3.3V Figure 7. Z-axis Zero-g leveland Sensitivity at 3.3V
5.2 Mechanical characteristics de rived from measurement in the
Figure 8. X-axis Zero-g level and Sensitivity change Vs temperature Figure 9. Y-axis Zero-g level and Sensitivity change Vs temperature Figure 10. Z-axis Zero-g level and Sensitivity change Vs temperature
5.3 Electrical characteristics at 25°C
Figure 11. Current consumption at 3.3V
6 Package information
conditions are also marked on the inner box label. ECOPACK is an ST trademark. ECOPACK specifications are available at: www.st.com. Figure 12. LGA 14: Mechanical Data & Package Dimensions
7 Revision history
Table 7. Document revision history 03-Oct-2006 1 Initial release.