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SILICON DESIGNS, INC
SENSOR: Capacitive Micromachined
Nitrogen Damped Hermetically Sealed ___ Low Noise: 5 g/Hz typical for 2g Full Scale Version Internal Temperature Sensor 4V Differential Output or 0.5V to 4.5V Single Ended Output Fully Calibrated Responds to DC & AC Acceleration -55 to +125 C Operation +5 VDC, 8 mA Power (typical) Non-Standard g Ranges Available Integrated Sensor & Amplifier LCC or J-Lead Surface Mount Package Serialized for Traceability Pin Compatible with Model 1210
Model 1221 LOW NOISE ANALOG ACCELEROMETER
ORDERING INFORMATION
Full Scale Acceleration 2 g 5 g 10 g 25 g 50 g 100 g 200 g 400 g Hermetic Packages 20 pin LCC 20 pin JLCC 1221L-002 1221J-002 1221L-005 1221J-005 1221L-010 1221J-010 1221L-025 1221J-025 1221L-050 1221J-050 1221L-100 1221J-100 1221L-200 1221J-200 1221L-400 1221J-400
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The Model 1221 is a low-cost, integrated accelerometer for use in zero to medium frequency instrumentation applications that require extremely low noise. The 2g version is ideally suited for seismic applications. Each miniature, hermetically sealed package combines a micro-machined capacitive sense element and a custom integrated circuit that includes a sense amplifier and differential output stage. It is relatively insensitive to temperature changes and thermal gradients. Each device is marked with a serial number on its bottom surface for traceability. An optional calibration test sheet (1221-TST) is also available which lists the measured bias, scale factor, linearity, operating current and frequency response.
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The Model 1221 produces two analog output voltages which vary with acceleration as shown in the figure below. The outputs can be used either in differential or single ended mode referenced to +2.5 volts. Two reference voltages, +5.0 and +2.5 volts (nominal), are required; the output scale factor is ratiometric to the +5 volt reference voltage, and both outputs at zero acceleration are equal to the +2.5 volt reference. The sensitive axis is perpendicular to the bottom of the package, with positive acceleration defined as a force pushing on the bottom of the package.
$33/,&$7,216
Seismic Monitoring Earthquake Detection Security Systems Machine Control Modal Analysis Instrumentation Appliances Robotics Crash Testing Vibration Monitoring Vibration Analysis Vehicle Dynamics
Silicon Designs, Inc. 1445 NW Mall Street, Issaquah, WA 98027-5344 web site: www.silicondesigns.com [page 1]
Phone: 425-391-8329
Fax: 425-391-0446 Aug 05
Model 1221 Low Noise Analog Accelerometer
6,*1$/'(6&5,37,216
VDD and GND (power): Pins (9,11,14) and (2,5,6,18,19) respectively. Power (+5 Volts DC) and ground. AOP and AON (output): Pins 12 and 16 respectively. Analog output voltages proportional to acceleration. The AOP voltage increases (AON decreases) with positive acceleration; at zero acceleration both outputs are nominally equal to the +2.5 volt reference. The device experiences positive (+1g) acceleration with its lid facing up in the earth's gravitational field. Either output can be used individually or the two outputs can be used differentially but differential mode is recommended for both lowest noise and highest accuracy operation. Voltages can be measured ratiometrically to VR for good accuracy without requiring a precision reference voltage. (See plot.) DV (input): Pin 4. Deflection Voltage. Normally left open. A test input that applies an electrostatic force to the sense element, simulating a positive acceleration. The nominal voltage at this pin is 1/2 VDD. DV voltages higher than required to bring the output to positive full scale may cause device damage. VR (input): Pin 3. Voltage Reference. Tie directly to VDD for ratiometric measurements or to a +5V reference for better absolute accuracy. A 0.1F bypass capacitor is recommended at this pin. 2.5 Volt (input): Pin 17. Voltage Reference. Tie to a resistive voltage divider from +5 volts or to a +2.5 volt reference voltage. IT (output): Pin 8. Temperature dependent current source. (May be tied to VDD; see full description on page 5).
!# # - by Model:
MODEL NUMBER
VDD=VR=5.0 VDC, TC=25C. 1221x-002 1221x-005 1221x-010 1221x-025 1221x-050 1221x-100 1221x-200 1221x-400 UNITS 5 10 25 50 100 200 400 g 0 - 600 0 - 1000 0 - 1500 0 - 2000 0 - 2500 0 - 3500 0 - 4000 Hz 800 400 160 80 40 20 10 mV/g 7 10 25 50 100 200 400 g/(root Hz) 2000 g Note 1: Single ended sensitivity is half of values shown.
Input Range 2 Frequency Response (Nominal, 3 dB) 0 - 400 2000 Sensitivity (Differential) 1 Output Noise (Differential, RMS, typical) 5 Max. Mechanical Shock (0.1 ms)
!# # - all Models:
PARAMETER Cross Axis Sensitivity Bias Calibration Error 2 Bias Temperature Shift (TC= -55 to +125C) 2
Unless otherwise specified VDD=VR=5.0 VDC, TC=25C, Differential Mode. MIN -002 -005 thru -200 -002 -005 thru -200 -250 TYP 2 2 1 100 50 1 MAX 3 4 2 300 200 2 250 0.5 1.0 2.0 UNITS % % of span (ppm of span)/C % ppm/C
Scale Factor Calibration Error 2, 3 Scale Factor Temperature Shift (TC= -55 to +125C) 2 -002 thru -050 Non-Linearity -100 & -200 (-90 to +90% of Full Scale) 2, 3 -400 Power Supply Rejection Ratio Output Impedance Operating Voltage Operating Current (IDD+IVR) 2 Mass: `L' package (add 0.06 grams for `J' package) Note 2: Tighter tolerances available on special order.
0.3 0.5 % of span 1.0 25 dB 90 Ohms 4.75 5.0 5.25 Volts 8 10 mA 0.62 grams Note 3: 100g and greater versions are tested from -65 to +65g.
SPECIFICATIONS SUBJECT TO CHANGE WITHOUT NOTICE
Silicon Designs, Inc. 1445 NW Mall Street, Issaquah, WA 98027-5344 web site: www.silicondesigns.com [page 2]
Phone: 425-391-8329
Fax: 425-391-0446 Aug 05
Model 1221 Low Noise Analog Accelerometer
$%62/87(0$;,0805$7,1*6 *
Case Operating Temperature . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . -55 to +125C Storage Temperature . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . -55 to +125C Acceleration Over-range . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2000g for 0.1 ms Voltage on VDD to GND . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . -0.5V to 6.5V Voltage on Any Pin (except DV) to GND 4 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . -0.5V to VDD+0.5V Voltage on DV to GND 5 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 15V Power Dissipation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 50 mW Note 4: Voltages on pins other than DV, GND or VDD may exceed 0.5 volt above or below the supply voltages provided the current is limited to 1 mA.. Note 5: The application of DV voltages higher than required to bring the output to positive full scale may cause device damage.
* NOTICE: Stresses greater than those listed above may cause permanent damage to the device. These are stress ratings only. Functional operation of the device at or above these conditions is not implied. Exposure to absolute maximum rating conditions for extended periods may affect device reliability.
PINOUT RECOMMENDED CONNECTIONS
(LCC & JLCC PACKAGES)
The 2.5V reference input (pin 17) may be driven from either a precision voltage source by the capacitively bypassed resistive divider shown above.
DEFLECTION VOLTAGE (DV) TEST INPUT: This test input applies an electrostatic force to the sense element, simulating a positive acceleration. It has a nominal input impedance of 32 k$ and a nominal open circuit voltage of 1/2 VDD. For best accuracy during normal operation, this input should be left unconnected or connected to a voltage source equal to 1/2 of the VDD supply. The change in differential output voltage (AOP - AON) is proportional to the square of the difference between the voltage applied to the DV input (VDV) and 1/2 VDD. Only positive shifts in the output voltage may be generated by applying voltage to the DV input. When voltage is applied to the DV input, it should be applied gradually. The application of DV voltages greater than required to bring the output to positive full scale may cause device damage. The proportionality constant (k) varies for each device and is not characterized.
1 ( A O P - A O N ) k (V D V - 2 V D D ) 2
ESD and LATCH-UP CONSIDERATIONS: The model 1221 accelerometer is a CMOS device subject to damage from large electrostatic discharges. Diode protection is provided on the inputs and outputs but care should be exercised during handling to assure that the device is placed only on a grounded conductive surface. Individuals and tools should be grounded before coming in contact with the device. Do not insert the model 1221 into (or remove it from) a powered socket.
SPECIFICATIONS SUBJECT TO CHANGE WITHOUT NOTICE
Silicon Designs, Inc. 1445 NW Mall Street, Issaquah, WA 98027-5344 web site: www.silicondesigns.com [page 3]
Phone: 425-391-8329
Fax: 425-391-0446 Aug 05
Model 1221 Low Noise Analog Accelerometer
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Bias temperature hysteresis can be minimized by temperature cycling your model 1221 accelerometer after it has been soldered to your circuit board. If possible, the assembled device should be exposed to ten cycles from -40 to +85C minimum (-55 to +125C recommended). The orientation to the Earth's gravitational field during temperature cycling should preferrably be in the same orientation as it will be in the final application. The accelerometer does not need to have power applied during this temperature cycling.
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DIM A B C D E F G H J K L *M N P R S *T *U INCHES MILLIMETERS MIN MAX MIN MAX 0.342 0.358 8.69 9.09 0.346 0.378 8.79 9.60 0.050 0.060 1.27 1.52 0.095 0.115 2.41 2.92 0.075 0.095 1.91 2.41 0.050 BSC 1.27 BSC 0.022 0.028 0.56 0.71 0.050 TYP 1.27 TYP 0.004 x 45 0.10 x 45 0.010 R TYP 0.25 R TYP 0.016 TYP 0.41 TYP 0.048 TYP 1.23 TYP .050 .070 1.27 1.78 .012 .020 0.30 0.51 0.03 R TYP 0.76 R TYP 45 MINIMUM 0.085 TYP 2.16 TYP 0.175 TYP 4.45 TYP
NOTES:
1. * 2. 3. 4. 5.
DIMENSIONS 'M', 'T' & 'U' LOCATE ACCELERATION SENSING ELEMENT'S CENTER OF MASS . LID IS ELECTRICALLY TIED TO TERMINAL 19 (GND). CONTROLLING DIMENSION: INCH. TERMINALS PLATED 60 MICRO-INCHES MIN GOLD OVER 80 MICRO-INCHES MIN NICKEL. PACKAGE: 90% MINIMUM ALUMINA (BLACK), LID: SOLDER SEALED KOVAR.
SPECIFICATIONS SUBJECT TO CHANGE WITHOUT NOTICE
Silicon Designs, Inc. 1445 NW Mall Street, Issaquah, WA 98027-5344 web site: www.silicondesigns.com [page 4]
Phone: 425-391-8329
Fax: 425-391-0446 Aug 05
Model 1221 Low Noise Analog Accelerometer
,17(51$/7(03(5$785(6(16,1*
The model 1221 accelerometer contains a temperature dependent current source that is output on pin 8. This signal is useful for measuring the internal temperature of the accelerometer so that any previously characterized bias and scale factor temperature dependence, for a particular accelerometer, can be corrected. The nominal output current at 25C is 500 A and the nominal sensitivity is 1.5 A/C. It is up to the user to characterize each device's exact output current versus temperature over the range it is to be used. Fluctuations in VDD & VR have little effect on the temperature reading. A reduction of 0.10 V to both VDD & VR will reduce the current about 1 A which corresponds to less than a 1C change in reading. With a single resistor RT = 2K between IT (pin 8) and GND, as shown in Figure 1, the output voltage VT will vary between +0.76 and +1.3 volts from -55 to +125C, which equates to a sensitivity of +3 mV/C.
V T R T (5 0 0 A ) + (1.5 A )(T - 2 5 )
[
[
]]
V T = R T (1.5 A ) T
If a greater voltage change versus temperature or a lower signal source impedance is needed, the circuit in Figure 2 can be used. With VOFF = -5V, gain resistor RG = 15.0K and offset resistor ROFF = 7.32K, the output voltage VT will vary between +4.5 and +0.5 Volts from -55 to +125C, which equates to a sensitivity of -29 mV/C.
V OFF + (5 00 A ) + (1.5 A )( T - 2 5 ) VT -RG R OFF
[
]
R OFF =
- V OFF
V T ( ) R G + (5 0 0 A ) + (1.5 A ) T - 2 5
[
]
RG =
(1.5 A )( T )
- V T
V T = - R G (1.5 A ) T
Figure 3 shows the voltage compliance of the temperature dependent current source (IT) at room temperature. The voltage at pin 8 must be kept in the 0 to +3V range in order to achieve proper temperature readings.
SPECIFICATIONS SUBJECT TO CHANGE WITHOUT NOTICE
Silicon Designs, Inc. 1445 NW Mall Street, Issaquah, WA 98027-5344 web site: www.silicondesigns.com [page 5]
Phone: 425-391-8329
Fax: 425-391-0446 Aug 05
Model 1221 Low Noise Analog Accelerometer
62/'(5,1*5(&200(1'$7,216
Reflow using a hotplate is the preferred method for assembling the model 1221 surface mount accelerometer to your Printed circuit board. Sn62 or Sn63 type solder is recommended. Hand soldering using a fine tipped soldering iron is possible but difficult without a steady hand and some form of visual magnification due to the small size of the connections. When using the hand solder iron method, it's best to purchase the J-Leaded version (1221J) for easier visual inspection of the finished solder joints.
Pre-Tinning of Accelerometer Leads is Recommended: To prevent gold migration embrittlement of the solder joints, it is best to pre-tin the accelerometer leads. The solder bath method of pre-tinning is not recommended due to the high degree of heat the interior of the device gets subjected to which may cause permanent shifts in the bias and scale factor. Instead, we recommend tinning one lead at a time, to prevent excessive heating of the accelerometer, using a fine-tipped solder iron and solder wire. Hotplate Attach Method using Solder Paste or Solder Wire: Apply solder to the circuit board's pads using Sn62 or Sn63 solder paste or pre-tin the pads using solder and a fine tipped soldering iron. If pre-tinning with an iron, apply flux to the tinned pads prior to placing the components. Place the accelerometer in its proper position onto the pasted or tinned pads then place the entire assembly onto a hotplate that has been pre-heated to 200C. Leave on hotplate only long enough for the solder to flow on all pads (DO NOT OVERHEAT!) Solder Iron Attach Method using Solder Paste: Apply solder paste to the circuit board's pads where the accelerometer will be attached. Place the accelerometer in its proper position onto the pasted pads. Press gently on the top of the accelerometer with an appropriate tool to keep it from moving and heat one of the corner pads, then an opposite corner pad with the soldering iron. Make sure the accelerometer is positioned so all 20 of its connections are centered on the board's pads. Once the two opposite corner pads are soldered, the part is secure to the board and you can work your way around soldering the remaining 18 connections. Allow the accelerometer to cool in between soldering each pin to prevent overheating. Solder Iron Attach Method using Solder Wire: Solder pre-tin two opposite corner pads on the circuit board where the accelerometer will be attached. Place the accelerometer in its proper position onto the board. Press gently on the top of the accelerometer and heat one of the corner pads that was tinned and the part will drop down through the solder and seat on the board. Do the same at the opposite corner pad that was tinned. Make sure the accelerometer is positioned so all 20 of its connections are centered on the board's pads. Once the two opposite corner pads are soldered, the part is secure to the board and you can work your way around soldering the remaining 18 connections. Allow the accelerometer to cool in between soldering each pin to prevent overheating. LCC & JLCC Solder Contact Plating Information: The plating composition and thickness for the solder pads and castellations on the "L" suffix (LCC) package are 100 to 225 micro-inches thick of gold (Au) over 80 to 350 micro-inches thick of nickel (Ni) over a minimum of 5 micro-inches thick of moly-manganese or tungsten refractory material. The leads for the "J" suffix (JLCC) package are made of CDA102 copper (Cu) have the same gold over nickel plating thicknesses as for the LCC pads. Recommended Solder Pad Pattern: The recommended solder pad size and shape for both the LCC and J-LCC packages is shown in the diagram and table below. These dimensions are recommendations only and may or may not be optimum for your particular soldering process.
DIM A B C D E F G
inch .230 .430 .100 .033 .050 .013 .120
mm 5.84 10.92 2.54 0.84 1.27 0.33 3.05
SPECIFICATIONS SUBJECT TO CHANGE WITHOUT NOTICE
Silicon Designs, Inc. 1445 NW Mall Street, Issaquah, WA 98027-5344 web site: www.silicondesigns.com [page 6]
Phone: 425-391-8329
Fax: 425-391-0446 Aug 05
APPLICATION NOTE
Model 1221 Accelerometer
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R1 = R2 = 5.00K 0.5% for precision 2.50V ref. C1 = C2 = 0.01 F ceramic
R3, R4, R5 & R6 = 20k6 to 50k6 R3 = R5 to within 0.1% for common mode rejection R4 = R6 to within 0.1% for common mode rejection R4 / R3 ratio accurate to within 0.1% for gain control R6 / R5 ratio accurate to within 0.1% for gain control
To achieve the highest resolution and lowest noise performance from your model 1221 accelerometer module, it should be connected to your voltage measurement instrument in a differential configuration using both the AOP and AON output signals. If your measurement instrument lacks differential input capability or you desire to use a differential input capable instrument in single ended mode, then the circuit above can be used to preserve the low noise performance of the model 1221 while using a single ended type connection. This circuit converts the 4 Volt differential output of the model 1221 accelerometer, centered at +2.5 Volts, to a single ended output centered about ground (0.0 Volts). It provides the advantage of low common mode noise by preventing the ground current of the model 1221 from causing an error in the voltage reading. The op-amp should be located as close as possible to your voltage monitoring equipment so that the majority of the signal path is differential. Any noise present along the differential path will affect both wires to the same degree and the op-amp will reject this noise because it is a common mode signal. The op-amp type is not critical; a A741 or 1/4 of a LM124 can be used. Both plus and minus supplies are needed for the op-amp to accommodate the positive and negative swings of the single ended output signal. The gain of the op-amp is determined by the ratio R4/R3 (where R4=R6 and R3=R5). If R3 through R6 are all the same value, the gain equals 1 and the output swing will be 4 Volts single ended with respect to ground. To obtain a 5 Volt single ended output, set R4/R3 = R6/R5 = 5/4 = 1.25. The single ended output of the op-amp will be centered at ground if R4 and C3 are tied to ground; using some other fixed voltage for this reference can shift the output. The value of the optional capacitors C3 and C4 (C3=C4) can be selected to roll off the frequency response to the frequency range of interest.
SPECIFICATIONS SUBJECT TO CHANGE WITHOUT NOTICE
Silicon Designs, Inc. 1445 NW Mall Street, Issaquah, WA 98027-5344 web site: www.silicondesigns.com [page 7]
Phone: 425-391-8329
Fax: 425-391-0446 Aug 05

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